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View Full Version : High voltage, low OTR pressure, related?



jelmore
07-03-2009, 07:20 PM
Had the OTR serviced about 3 months ago. Added 4 lbs 134A and some dye for leak detection later.

A week ago, the OTR didn't seems quite cold, but after about 10 minutes it seemed to work ok, though not really, really cold. Checked the refrigerant levels and the bottom sight glass seemed full and practically nothing in the top sight glass. The compressor oil looked a tad low, but it was showing in its sight glass, sloshing around.

Yesterday while under way the Hi/Low 24v voltage indicator on the dash was showing sporadically, never more than 3 seconds, and sometimes flickering. The analog voltage gauge shows pretty much topped out, just below 28v.

Turning on the 12v headlights seems to suck enough voltage to eliminate that hi/low warning light. Maybe the 24v regulator needs a slight adjustment. I think I can do that.

Today, though a nice day, I thought I'd run the OTR, and draw down some volts. Five minutes later, the OTR high pressure and OTR low pressure lights came on, the same indication as when I was low on refrigerant.

Turned off the OTR, a few minutes later the hi/low voltage light came on, turned on the headlights and no hi/low voltage warning.

Parked in high idle for 15 minutes, no headlights and no warning lights.

Haven't turned the OTR back on.

If you're still following this, are these events possibly related?

Jon Wehrenberg
07-03-2009, 07:57 PM
Jim,

What was the actual voltage as shown on the gauge?

If the voltage indication light was really telling of a problem such as low voltage and it affected the condensing coil blower then the two can be related. A failed or slow running condenser motor would not pull enough air across the condenser and the AC system refrigerant pressure would increase causing the unit to shut down or at least give the warning.

jelmore
07-03-2009, 08:19 PM
Jon, would high voltage have a similar effect? The actual voltage (as best I could tell) was 28v. Liberty manual says the hi/lo indicator turns on when the batteries are >30v or <24v.

I'm running now with the wabasto on (coldest temp) to run some 24v fans (I presume) and the voltage on the dial is 27.5v. I'm also running the headlights and the 12v side reads 13.3v/13.2v. No hi/lo warning for 50 mies. Jon--don't flip out it's Linda doing the typing!

Jon Wehrenberg
07-04-2009, 07:55 AM
The reason I asked about actual voltage is because the Vanner monitor (in the rear above the chassis batteries) has failed on some coaches giving incorrect warnings.

It does not monitor the OTR so I am still trying to figure out how the AC warning light relates to all this.

If you get the Hi/Lo warning light again for chassis voltage check the voltmeter and see what it reads. At least that is easily checked.

jelmore
07-04-2009, 08:15 PM
I'm thinking the OTR and voltage are not related. The OTR pressure warning isn't voltage dependent I don't think, so the only voltage effect would be on the condenser fans like you said. I'm seeing high voltage, so unless that blew a fan breaker I don't know about yet, then I guess I need to be looking at the actual voltages at the regulator and monitor; the OTR air can be dealt with later. I don't know about the equalizer. I've never seen exactly double the 12v voltage on the 24v gauge; the 24v side has always been a little higher. I don't know that I have the literature to test it.

I hope you're right on the monitor malfunctioning. I'm anxious to check that out. That would sure ease the angst.

Happy 4th, from Saint Ignace, Michigan.

Jon Wehrenberg
07-05-2009, 08:27 AM
Jim,

You are mixing apples, oranges and peaches. Doing on-line analysis of problems is difficult because there are so many clues available when a person has some tools or meters and is standing next to the coach and on-line we have to ask and assume. Your last post suggests you are mixing up house and chassis electric readings.

Let me see if I can help you sort things out.

First, if you do not have a good multi-tester, you should get one. If for no other reason than to be able to obtain voltage readings not available from the coach gauges, and to check for power and open circuits. I will assume you have one, or for the moment you can borrow one.

Your 24 volt gauge is the chassis voltage. It only reflects the output of the alternator for the chassis (the big alternator). Your chassis electrical system alone is monitored by the Vanner electrical monitor. The only equalizer you should have is the 100 amp equalizer above the chassis batteries.

The voltage you should see at the 24 volt battery post, at the 24 volt equalizer post, and at the dash gauge is about 28 volts with the engine running on high idle, and with the engine off, and no loads you should see 25.5 (approximately). At the 12 volt equalizer post you should see one half the 24 volt value within 1/2 volt or 14 volts and 12.75 volts respectively.

If the actual voltage is around those values your chassis electrical system is OK. Those values will change downward as you put loads on the chassis electrical system, such as running the OTR or bus lights. With a healthy alternator and a voltage regulator working as they should the voltage drop will be minimal with the engine running.

Your comment about 12 volts suggests to me that you are interpreting the house voltage gauge as a reading of the chassis 12 volt systems. That is not correct. The house and chassis on your coach never merge. I believe you have a separate house alternator, likely driven from the fan pulley. That house system has no dash warning lights and is not a part of the issues you are discusssing. But just for your info, with the engine running the house voltage should be around 14 volts, and with the engine off and no house loads it should be around 12.75.

As to voltages affecting the OTR.....higher than acceptable voltages (30 volts for example) are not good, but it is unlikely they will shut down the OTR system or motors. Actually as voltage increases the motors draw less current so it is unlikely the OTR circuit breakers will trip. As the voltage drops however, the current draw increases and then the CBs will trip, but if they do trip you will have to reset them before the AC system will function. Your description of problems with the AC does not inidcate a tripped breaker. It may be coincidence the electrical HI/Low indicator is coming on when the AC warning is coming on.

phorner
07-05-2009, 08:58 AM
Jon, my set-up is exactly as you described.

Jim, after reading your postings, is it at all possible that the HI/LO dash warning was the OTR AC pressure instead of the voltage?

If the indicator only came on for a second, especially while driving, could they have been mistaken?

jelmore
07-05-2009, 10:01 AM
Jon, I have a 12v display and a 24v gauge that are both reading chassis voltages. The 12v display is part of what Liberty calls the Message Display Center. It's an LCD display is the lower left corner of the dash that also provides, among other things, engine oil and transmission retarder temps. The 24v gauge is a separate item. I have a multi-tester and will check the voltages when I can start up the bus without bothering the folks around me.

Paul, I'm sure I saw both types of warning. And I don't think they're related. They didn't happen at the exact same time, just during the same driving period.

I find it interesting that there was no voltage warning while stopped in fast idle; only while under way, and while under way it was sporadic. Almost makes me suspect a loose connection.

phorner
07-05-2009, 10:12 AM
Jim,

FWIW, I had an intermittent indication on the dash warning lights of hi/low chassis voltage. Usually, it would come on when I first started up the bus and then be OK. Sometimes it would stay on for a few minutes and then go out.

I finally caught this display long enough to compare with the voltage gauge and, sure enough, the actual voltage was too low, then swing to correct.

As it turned out, this was an early indication of a failing voltage regulator. Took a while before it finally failed, as this occurred over several thousand miles and a few months.

jelmore
07-05-2009, 10:23 AM
Paul, Prevost replaced the voltage regulator, along with the chassis batteries, a year ago. The voltage regulator is the new style, whatever that means. It looks like it has red loctite all over the adjustment screw, so before I mess with adjusting something, I need to check everything else out. Thanks for all the help.

When I take a voltage reading at the regulator, what is that voltage ... batteries? alternator? Are they the same? The field wire, is that what tells the alternator how much to put out?

phorner
07-05-2009, 10:49 AM
Jim,

The measurement at the regulator with the engine running should be charging voltage.

Jon helped me through the diagnostics..... he's your guy there.

truk4u
07-05-2009, 12:46 PM
Jim,

If you want to check your alternator voltage, check at the batteries while the bus is running on high idle.

If your equalizer has a little led light, you can check it to make sure it is working properly. With the bus off, turn on the headlights and the little light on the equalizer should be on steady.

The Vanner monitors are many times the culprit. With your meter in hand, call Vanner and they will walk you through the diagnostics, they are very helpful. I almost got talked into a new equalizer when in fact it was the monitor and ran about 80 bucks vs 1000. They also have updated the monitors and you probably have an older one.

Jon covered everything well, so I don't have much to add.

Jon Wehrenberg
07-05-2009, 03:00 PM
Jim,

Since you have the voltmeter I would keep it simple and check the voltages at the equalizer with the bus not running, and then with the bus running.

Checking both the 24 volt post and the 12 volt post, not running and running will tell you everything you need to know. That will verify if the alternator is charging and it will verify the equalizer is equalizing. You will note if the batteries need a charge that you can see the 24 volt side cycle up and down as the equalizer is adjusting the 12 volt side. You may even hear the internal relay in the equalizer clicking. But Paul made an important observation. He could see voltages that were not right for a while before his regulator finally died. As a pilot I tend to really watch the gauges, and I can tell you if my gauges are so much as a needle width different than normal I am working to find out why. I would suggest you monitor and record your gauges do determine what is normal, keeping in mind on electrical stuff it is also important to recognize the loads that are on the system.

jelmore
07-05-2009, 10:18 PM
Thanks you guys. Great help. I'll probably get to this tomorrow. Meanwhile, speaking of loads, I found it curious that while monitoring my transmission retarder temperature, when I turn on the headlights, the temperature display increases about 10 degrees. I don't know if that's a recent thing or just something I've never noticed before.

Jon Wehrenberg
07-06-2009, 08:35 AM
That's an interesting observation.

This is a piece of trivia, but it may be worth following with a call to Prevost.

Way back when we had a 87 vintage coach with DDEC I. Prevost had a recall to change the wiring because the headlights and the DDEC were on the 12V side of the chassis electrical system, and turning the headlights on would drop the voltage to the DDEC.

Prevost revised the wiring in the front electric compartment so the DDEC was not affected by turning on the headlights.

How this relates to the 10 degree temperature change I do not know, but since the transmission computer is generating that temperature readout it makes me wonder if some or all of the funky conditions Jim is describing may all be tied together and are the result of some obscure problem.

jelmore
07-06-2009, 08:50 AM
Yes, Jon, that IS very interesting. I hadn't mentioned it I don't think, but also turning on the headlights drops the 12v display down about .5 volts. Normal reading while under way is 13.6-13.8v. With the headlights, 13.1-13.3v.

Jon Wehrenberg
07-06-2009, 09:12 AM
What we now need is for folks that are driving today, and have a fully charged set of chassis batteries to post the 12 and 24 volt readings with no chassis electrical loads, and then to turn on the headlights and post the voltages.

I have never paid close attention to the chassis voltages with the headlights on and off, but do know running the OTR does drop the chassis battery voltage a little. Since that is normal and expected I never gave it any further thought.

I cannot compare my coach to yours directly because I have a single large alternator and I have house and chassis loads affecting output. We need others with separate house and chassis alternators to post.

phorner
07-07-2009, 01:03 PM
OK, so in an effort to add to the collective data base, I took the bus out to burn some diesel and provide some voltage numbers.

With fully charged chassis batteries, and driving at 1500 rpm with the OTR on, I was reading a consistent 13.4 volts. Starting out at 13.5, but after a few minutes of driving settled down to 13.4

Turning the headlights on under the same conditions (1500 rpm, OTR on) dropped the voltage to 13.1 volts. Tried this several times with the same results.

Turning the headlights on under the same conditions but WITHOUT the OTR on (the sacrifices I make!) dropped the voltage to 13.2 volts.

Once again, cruising at 1500 with the headlights off and OTR on returned to a very consistent 13.4 volts. And interesting note, the voltage would then drop to 13.0 at low idle while stopped in traffic.

My bus has the separate 12 volt alternator for the house batteries, so any house loads during this test should not have influenced the numbers.

Hope this helps....

jelmore
07-07-2009, 01:23 PM
Paul, thanks for your sacrifice. Did you happen to notice what your 24v gauge was showing?

You see a drop in 12v voltage under load just as I do. However, without a load, my 12v display is from 13.6-13.8v, a little higher than yours.

I'm in the middle of testing things now. Getting ready to learn a lot.

jelmore
07-07-2009, 01:46 PM
In testing the equalizer, in addition to checking voltages, the Vanner instructions says to check with an ammeter all the wires attached to the 12v stud. I don't have one of those wrap around ammeters, but my multi-tester will read amperage. Would reading the amperage from the 12v post on the equalizer to the post it connects to on the battery be the same as using an wrap around ammeter?

Jon Wehrenberg
07-07-2009, 03:29 PM
Yes, but isn't your question regarding voltage, and if so why not just check them for a start?

Also, most multitesters have a limit of around 10 amps, which on 12 or 24 volts isn't much of a load.

jelmore
07-07-2009, 03:50 PM
Jon, the Vanner instructions say with the engine running, turn on a 12v load such as headlights, check the 24v + ground. If between 25.5v and 29v, check amperage on the wires connected to the 12v terminal. If > 3 amps, the equalizer is ok. If not, there's a series of additional tests.

I'm so lame, I've already fried a set of leads with alligator clips trying to do that ammeter test. I'll try again.

Voltage readings have been:

Engine off, batteries rested...
24v + gnd = 25.33
12v + gnd = 12.55
24v + 12v = 12.78

Engine on, no 12v load...
24v + gnd = 28.15
12v + gnd = 14.03
24v + 12v = 14.12

Engine on, headlights on...
24v + gnd = 28.16
12v + gnd = 13.95
24v + 12v = 14.21

Interesting the difference between 12 + gnd and the 24v + 12v.

Jon Wehrenberg
07-07-2009, 05:05 PM
I would say you now know two things. First, the chassis alternator is charging and is being properly regulated, and second the equalizer is working.

My voltages with the engine running are less, however my alternator (single large one) charges house and chassis, and may have been set to not overscharge gel cell house batteries. I run around 27.8 volts.

The voltage drop with headlights on is certainly expected and I do not see high or low voltages or any spread to indicate an equalizer problem.

When the hi/lo voltage light comes on again, if possible try to see what voltages you are getting, at the dash is OK, but at the equalizer as you did is better. If the voltages are where they are right now I suspect the Vanner monitor is malfuncting (a highly technical term).

jelmore
07-07-2009, 07:31 PM
Jon, I like "malfuncting." I'll add that to my increasingly vast Prevost vocabulary.

Talked to Vanner, and since I don't have a real ammeter to check whether or not the equalizer is equalizing, Doug gave me this test: engine off, 12v load on such as headlights, check voltage on 12v+gnd and compare to 12v+24v. Do this over enough time for the batteries to lose .2v. I did that for about 45 minutes and the 12v+gnd went from 12.03 to 11.96 and the 12v+24v went from 12.78 to 12.65. Perhaps I didn't let it run long enough. Doug explained there is a timer delay and it could take 10 minutes for the equalizer to kick in.

I called Doug back but Vanner was closed for the day. Not sure what those numbers mean, but Doug will.

It looks like the equalizer isn't doing anything. Maybe there wasn't enough load, but I don't know how to add any more significant 12v load.

The regulator is reading 28.19 and I think my books say it should read 27.5.

Maybe all I need to do is turn down the regulator.

Doug suggested, as you did, to check voltage at the equalizer or batteries while running. I can just see the duct tape on the side of the bus with wires running up to my voltmeter. I guess there is no other way, eh?

Jon Wehrenberg
07-07-2009, 08:19 PM
Jim,

Don't look for problems you do not have. They will come to you.

Your equalizer is working. I have my neck out a country mile saying that, but the fact that the voltages were the proper ratio tells me it is OK. If is was not working your 12 volts would not be half of your 24 volt values. You are well within the .5 volt tolerance.

There is a time delay for the equalizer to read a drop in 12 volt values and to make the adjustment to bring it within the specified range. You can hear it if you leave the engine off and turn on the chassis battery charger. I think it is maybe a minute or so delay. There is a distinct click and even if you do not hear the sound, measuring the 24 volt side at the batteries you will see the voltage slowly ramp up and then drop down, and ramp up again. The spread is only about .3 or .4 volt, but it is the equalizer directing the charge to the 12 volt side.

I'm not sure you need to turn down the regulator. Or maybe I am thinking of the bulk and absorbtion voltages for lead acid batteries. They are typically where your voltages are. FWIW my plane system runs at 28.2 and I have no battery problems. If the book says 27.5 then that is where you should set it, but before doing that you might want to read up on battery info to see if your current set point is what the battery folks suggest. Unlike my coach where I am charging other than lead acid I can understand why my voltages are lower, especially if the coach came with gel cell.

jelmore
07-08-2009, 08:54 PM
According to Doug at Vanner, the equalizer tested out ok from that last test. Ok, since the 12v+gnd and the 12v+24v went down the same amount while under load.

The Prevost electrical manual says that in the event of high battery voltage, turn down the regulator .3v and see how that does over a few days. I turned it down from 28.19v to 27.80v. Vanner doesn't think it is a monitor problem. Doug said that when they go bad, it's all the way bad all at once, not intermittent. He also suggested there may be a not very good ground somewhere. Oh boy!

Rodney at Prevost Ft. Worth, by the way, diagnosed either a bad battery or equalizer. That's where they would look first. Also, he said a high battery voltage condition will shut down the OTR.

Jon Wehrenberg
07-09-2009, 08:13 AM
I trust the advice Vanner gave. I am not so sure about the monitor comment however. Dan S should post here, but if I recall he kept getting intermittant hi/lo and it was the monitor. I think Truk replaced a monitor once also. Forgot how his problem acted.

I see the 28.2 volts at the high end of the range, but not an overvoltage condition by any stretch of the imagination. I do agree with turning down the regulator.

I would like to know where in the OTR system there is overvoltage protection, or to be more precise, what will cause it to stop functioning if the voltage gets too high, and what voltage is too high? Perhaps Rodney can explain this. Also I have never heard of a bad battery causing a high voltage situation. I am wondering why he would suggest that. BTW, equalizers do not step up the voltage. They just insure that the 12 volt side is half of the system 24 volt value. Why would he focus on the equalizer? I'm critical because it is morning and I have not had my second cup of coffee.

truk4u
07-09-2009, 09:23 AM
I did have to change out a monitor on Jamie's CC and it was intermittent.

Danss
07-09-2009, 09:52 AM
I did have same problem for all of a 1 week trip. After consulting with the experts on POG I ordered and replaced the vanner control unit. Corrected problem and was a lot cheaper than chasing down and changing some batteries. Good Luck

jelmore
07-09-2009, 10:16 AM
I'll be traveling today and see how it does.

Odd that the hi/low light does not come on while in high idle, but only while under way. And that applying a load while underway makes the light go away.

Odd also that Vanner and Prevost both suspected a battery or the equalizer. Vanner had me check the equalizer (and he kept mentioning out of balance, which I repeatedly said was not the issue).

I have had an episode of serious voltage spikes in the past, but that was a loose battery cable (installed by Prevost).

jelmore
07-09-2009, 07:35 PM
A couple of hundred miles today. No electrical issues at all. It might have been nothing more than a loose connection at the monitor. I reseated all the connections while tidying up. All voltages are where they should be and they stay that way. I sure learned a lot.

Asked Rodney at Prevost Ft. Worth about that high voltage shutting down the OTR. Boy, did he fumble and mumble. "Well, maybe it's the low voltage that, uh, might cause, uh, some problems, uh . . . ".

The OTR is still going out. That has to be a separate issue. I'll do some poking around based on the long read in the manual. Maybe someone in Green Bay can do something with it. Meanwhile, generator and Cruise Airs. Nice to have some options.

Jon Wehrenberg
07-09-2009, 09:28 PM
Jim,

Long shot, and difficult to help you when we are not standing next to the bus, but if you get a chance pop one or two of the brushes for the condenser fan motor. I don't know if yours is like earlier models that I have had, but the brushes are easily removed for inspection. If my memory is working the minimum length is 3/4". Intermittent OTR operation could be caused by something as simple as a condenser fan motor operating imtermittently.

Thanks for the update on the OTR over voltage shutdown. It sounded unreasonable.

You still could have a Vanner monitor acting up, but at least dropping the voltage has now made the immediate problem go away. Again, going by memory, the monitor treats 30 volts as hi voltage.

jelmore
07-23-2009, 10:09 AM
This might wrap this thread up. Maybe it will be helpful to others.

The hi/low warning light has mostly gone away. Turning down the voltage at the regulator made some difference. I've checked 12v and 24v coming into the monitor and those voltages are steady and right where they should be. I thought I had caught it when it was acting up, but could have missed the event. I suppose I should order a monitor and keep it handy in case this one acts up again.

The OTR, of course, is not related to this particular hi/low voltage issue. CB1 is fine, motor brushes are fine, relays are fine, the condenser fan cycles. Driving the other day, I left the unit on after the hi pressure and low pressure warning lights came on and in about a minute the lights went off and the unit was cooling again. Anywhere from a minute to five minutes later, the lights would come on again. This cycle continued all afternoon. Went to a Carrier truck service center. All pressures in the system normal when it is working, refrigerant level is normal, everything fine except a refrigerant solenoid valve right after the moister indicator. That valve was freezing up indicating it wasn't opening. After further checks on the system and driving pressures way up, that valve came back to life and all is functioning normally. The tech supposed there must have been a little "junk" in the system and getting pressures up, checking things and spending some money fixed it.

I need a thorough tour of the OTR system by a Prevost expert. There are some things that the Carrier guys didn't know about this type of installation.

Hope this has been helpful. I'm never amazed by how little I know.

phorner
07-23-2009, 10:46 AM
Jim,

A guided tour of the OTR system would be very beneficial to me too.

It's interesting that in the manual, they describe the High Air Conditioning (A/C) Pressure indicator with a note " In hot weather, the High A/C pressure indicator may light up. This is not an abnormal condition."

Well gee whiz..... that's exactly when I expect to be using mine!

And, what is "hot" weather anyway ??

Thanks for keeping us up to date with this.

GDeen
07-23-2009, 10:56 AM
I need a thorough tour of the OTR system by a Prevost expert. There are some things that the Carrier guys didn't know about this type of installation.



Right with you there - wonder if we could get something going in OKC???

Jon Wehrenberg
07-23-2009, 11:37 AM
Again, not encumbered by actual knowledge of the system, if it actually has a solenoid valve that opens and closes when required it sounds like for whatever reason it's ability to open (or stay open) as required is intermittent.

Since mechanical devices never repair themselves this could pose a problem in the future and cause the OTR system to fail to function. What concerns me are high system pressures. The high system pressures and the failure of the seal behind the clutch on the compressor which in turn eventually caused and then fed the fire in my engine compartment on the first coach.

The compressor is a six cylinder one and it has the ability to pump some high pressures if the system downstream gets shut down. That is why on the top of the compressor are all the pressure switches and wires. They will shut the compressor down if pressures exceed certain values. On my coach the Wizards that repaired the system left the unloader valves off so the system did not have the over pressure protection. If there is something causing an over pressure situation, keep in mind your only remaining protection is those pressure switches, and you are betting that one of them will not fail.

phorner
07-23-2009, 12:46 PM
Jon,

That picture gives me chills every time I see it.....:eek:

A valuable lesson indeed.

Jon Wehrenberg
07-23-2009, 01:09 PM
You had to be there Paul if you think a picture will shake you up.

The freon escaping from the failed seal behind the clutch was coming out under pressure and carrying compressor oil with it, making it a very effective blowtorch.

I thought a picture would be worth a thousand words to illustrate my point.

GDeen
07-23-2009, 01:13 PM
Ok, so how about an OTR donkey show for us noobs in OKC so we can avoid this type of disaster???:cool:

jelmore
07-23-2009, 01:21 PM
From what I was told, that solenoid valve is what releases the refrigerant to the expansion valve. It's electrical. Where it gets its instructions, I don't know. There is (supposed to be) another one of these valves for the driver air system. The normal state for those valves is closed and the solenoid opens the valve. The normal closed state can be overridden manually. It's curious that my Prevost manual doesn't show that valve.

The high pressures that were generated were by keeping the condenser door open. The unloading solenoids and clutch were working fine.

All fine so far. No fires yet. Insurance is paid up.

Jon Wehrenberg
07-23-2009, 04:01 PM
Gordon,

Jim has it right. When the system senses high pressure from the solenoid valve being closed (that is the first time I ever knew one existed on the system. thanks Jim) his high pressure switches on top of the the compressor open the circuit to the clutch and it disengages. They also trigger the warning light.

In the case of my coach it had mechanical unloader valves that the Carrier techs INTENTIONALLY removed saying the pressures would never get high enough to even actiuate them. There was no warning light to indicate excessive pressures. In my case the warning light was flames. If it was night time I bet the sight would have been impressive. In the daytime you cannot see the flames in your mirror or camera.

Our systems now are supposed to self protect us and we have no control over them. As long as everything works we are OK.

In Jim's case it sounds as though his solenoid valve is malfuncting (a very technical term). So now I know there are a couple of reasons why we would get high pressures. The first and most common is the failure of the condensing coil fan which could be due to brushes worn out, a tripped CB, or some associated reason why the coils are not getting enough air across them. The second reason now is the previously unknown solenoid valve not opening allowing the flow of refrigerant.

GDeen
07-23-2009, 05:43 PM
Thanks for the info Jim and Jon. I would love to see a walk through of the entire system, and cruiseairs for that matter. Would be nice if we could re-visit some of the prior successful tech seminars for the new POGGERs to help our continued understanding of these machines.


Gordon,

Jim has it right. When the system senses high pressure from the solenoid valve being closed (that is the first time I ever knew one existed on the system. thanks Jim) his high pressure switches on top of the the compressor open the circuit to the clutch and it disengages. They also trigger the warning light.

In the case of my coach it had mechanical unloader valves that the Carrier techs INTENTIONALLY removed saying the pressures would never get high enough to even actiuate them. There was no warning light to indicate excessive pressures. In my case the warning light was flames. If it was night time I bet the sight would have been impressive. In the daytime you cannot see the flames in your mirror or camera.

Our systems now are supposed to self protect us and we have no control over them. As long as everything works we are OK.

In Jim's case it sounds as though his solenoid valve is malfuncting (a very technical term). So now I know there are a couple of reasons why we would get high pressures. The first and most common is the failure of the condensing coil fan which could be due to brushes worn out, a tripped CB, or some associated reason why the coils are not getting enough air across them. The second reason now is the previously unknown solenoid valve not opening allowing the flow of refrigerant.

truk4u
07-23-2009, 09:11 PM
King,

After reading this, don't you wish you had Prevost OTR?:eek:

rfoster
07-23-2009, 11:12 PM
Truk: Been there - have not done that.

I guess I will stick to my funeral home fan from Denny.

Yall have big fun up north and send pictures now ya hear.

truk4u
07-24-2009, 09:15 AM
Could'nt go to Osh, stuck at home!:mad: