OTR air

[sticks]

Experiencing a problem with my OTR heat/air on my way from Iowa to Florida. After 3 days of fog, rain, and road grime, the passenger heat/air unit would shut off seemingly when pulling off interstate and driving slowly or ready to stop. It would not turn back on pushing the on/off button for 30-60 seconds. Is something overheating and thus shutting down? Are there filters under the bus that have gotten dirty creating this problem? I.m all ears.thanks!!

[Jon Wehrenberg]

What is passenger OTR?

I am not up to speed on later model H3 OTR systems, or how Prevost set up the controls. My controls for OTR consist of a rocker switch to set heat or AC, and controls for the temp and fan speed.

The driver's portion of the system is the front ducts only, and for heat can be run without the main OTR switch being on, but the AC function requires the OTR AC function to be on.

I have no button to push or reset.

You don't say whether you were calling for heat or AC. Any warning lights? Is it the fan that quits, or does the fan continue to run but the temperature fails to heat or cool?

It is highly improbable that a few days running in crud has any affect on the system because these systems run on commercial buses that run in those conditions for a long time with minimal maintenance.

[rfoster]

You need an A1 Fan.

[jack14r]

Sticks,The switch for the dash as well as the switch for the rest of the coach must be on for the system to work,my 05 Liberty would show a webasto light on the dash whenever the heat came on,this indicated that the webasto pump was on which circulated the hot water to the heat exchangers throughout the coach.I would check the Webasto pump as well as solenoids that allow the coolant to flow to the dash heat exchanger.Being in warranty,this is a Liberty job.

[sticks]

mystery solved. There are two small wires on top of the alternator that feed the OTR system. One or both can vibrate loose over time or break , either way, the OTR stops working . In my case , I probably had one to start with which intermittently stopped passenger side but by the next day the whole system went belly up for good but I was able to limp into Stuart, Fla. in 84 degree weather and get it repaired.Turning generator on, opening front shudders and running Cruise airs helped cool the back of the coach, but doesn't do anything for the driver( me).

[GDeen]

mystery solved. There are two small wires on top of the alternator that feed the OTR system. One or both can vibrate loose over time or break , either way, the OTR stops working . In my case , I probably had one to start with which intermittently stopped passenger side but by the next day the whole system went belly up for good but I was able to limp into Stuart, Fla. in 84 degree weather and get it repaired.Turning generator on, opening front shudders and running Cruise airs helped cool the back of the coach, but doesn't do anything for the driver( me).

Imagine that was especially true in the H.....

[garyde]

Hi Sticks. If your OTR is working for the rest of the Coach, it may be a vent problem only. I have heard that the front vent hoses can collapse or seperate.

[Jon Wehrenberg]

Huh???????

Wires off alternator make the OTR work???????

[JIM CHALOUPKA]

How about wires off alternator and nothing works. :eek:





:pjim

[Jon Wehrenberg]

The alternator on my bus has three wires, the big cable going to the isolator, a field wire to the regulator, and a relay wire.

If they are loose the bus loses voltage in the chassis batteries, and the AC is a heavy load pulling juice from the batteries, but before the batteries go dead there is a big red warning light on the dash saying the alternator ain't alternating.

[truk4u]

Alternator wires running direct to the OTR doesn't make any sense!

[Jerry Winchester]

If the driver's air is not working (cooling) is could be the expansion valve. In that issue, coach air is cold, but driver air is not.

[tdelorme]

OK, guys. Sticks says nothing about the loose wires being part of the alternator system. The loose wires apparently run in the general area of the top of the alternator. Jon, remember in OKC when my OTR air was not working. Same deal, broken wire that had been rubbed by the alternator pully caused the failure.

[Loc]

Another good reason to avoid an OTR coach. At least it has slides.:D

[GDeen]

Sounds like he said the OTR didn't work at all and he had to use the cruiseairs instead....particularly in the H3, that would leave the driver pretty isolated without A/C....

Loc, you should be in hiding after Brown won Teddy's seat - the first step in the new populist agenda for the white house is to come after those of you who caused all this economic trouble in the first place....:cool:

[garyde]

Sounds like he said the OTR didn't work at all and he had to use the cruiseairs instead....particularly in the H3, that would leave the driver pretty isolated without A/C....

Loc, you should be in hiding after Brown won Teddy's seat - the first step in the new populist agenda for the white house is to come after those of you who caused all this economic trouble in the first place....:cool:


Lets keep it clean. No Politics please.

[GDeen]

Jeez Gary, just jerking Loc's chain.......wasn't aware of the new rules so thanks for keeping me straightened out.

[sticks]

Sorry for my uneducated second hand explanation of my OTR wiring malfunction, I'm an eye surgeon by training not an electrician. In fact, electric circuits always eluded me when I took physics. " tells the ak seemed like something " not for man to know". At any rate, the two small wires coming off the top and back of the alternator , apparently , are notorious for vibrating loose over time ( or breaking like mine). One of these wire goes to a relay that " activates" the OTR and the other small wire "tells the alternator to charge the chassis batteries" Hows that for a noobe novice electrically challenged explanation?

[Jon Wehrenberg]

We understand. Trust me.

Those wires relate solely to the alternator and its operation. I think. I have to look at a wiring diagram to see what's what because it does not seem reasonable for the OTR to be controlled from the alternator, however there may be something in the circuit that prevents the AC from running below a certain voltage, the current drop caused by a loose wire.

It still does not compute in my brain why you did not get a warning light for voltage on the dash. Or did you?

[sticks]

Jon, I had no red battery warning light show up on the dash when my OTR system shut down only during very low or idle speeds the last 2 or 3 hours of driving time. My primitive brain was wondering at this time whether voltage was crossing this compromised wire at higher speeds but not at idle speed. At any rate, once both wires definitely parted ways the red battery warning light came on and the OTR shut down permanently and I was " toast" for the remainder of the trip to Stuart, Fla.

[GDeen]

Jon, I had no red battery warning light show up on the dash when my OTR system shut down only during very low or idle speeds the last 2 or 3 hours of driving time. My primitive brain was wondering at this time whether voltage was crossing this compromised wire at higher speeds but not at idle speed. At any rate, once both wires definitely parted ways the red battery warning light came on and the OTR shut down permanently and I was " toast" for the remainder of the trip to Stuart, Fla.

To me that is the biggest potential drawback of the OTR system - if it goes down and you have to switch to cruiseair, no air for the driver up front. As Jerry pointed out, this would also be the case if the expansion valve on the drivers portion of the system crapped out as well. Still, nothing like OTR air for cooling the coach and driver when it is on.:D

Seems like it would make some sense the way Sticks thinks his is set up - eg, if the alternator craps out it sends a signal to the relay to shut down the OTR to preserve battery power?? That would at least stop battery draw before it learns of low voltage from the batteries or invertors after it has already happened?

Jon, would you think that OTR wiring is a convertor specific setup or Prevost since it deals with the chassis air? If Prevost, then all coaches should be wired the same I would think.

In any case, another one of those maintenance things it sound like worthwhile to add to the periodic checklist.

[Jon Wehrenberg]

Stick,

Now it makes more sense. You were not charging the chassis batteries due to loose alternator wires, and it appears that in turn was the gremlin that caused the OTR to stop functioning properly.

The OTR takes a lot of juice and that is why buses with OTR always have the big alternator dedicated to the chassis.

Gordon,

Stick was getting a warning light, but as he pointed out it was originally occurring at low RPM or idle. You should never ever get a red light on the electrical system if the bus engine is running, even at low idle with the OTR on. So he was being warned, but did not understand that unlike some cars of a bygone era this was not normal. As a new owner all of us go through that phase where we do not know what we don't know. His alternator explaination makes sense in the context that his loose alternator wires did affect the OTR, but only because the voltage was low.

As to Cruise Airs, and Stick's Liberty this is another case where some understanding would have kept him comfortable. First, lets start with the worst scenario where his alternator quit functioning due to those loose wires. At that point he could have cranked up the generator, run all his cruise airs and he would have been very comfortable. He would have been automatically charging the house batteries through the inverters because as the alternator quit functioning his house power was dropping also, and finally if his coach is equipped as I suspect it is with an engine battery charger he could have turned that on to at least keep the voltage up for the chassis or maybe even bring them back up to a full charge until the alternator issue could be resolved.

The way Liberty sets up the cruise airs (four in his case) the two center ones move air forward and rearward, and the front one cools the front area. He would have been very comfortable, and if he wanted to move even more air he could run the driver's area fan so he had air flow from the normal front vents.

We have had OTR for 20 years now and the first coach was 15 to 17 years old before it needed any service with the exception of a weak circuit breaker for the condenser fan. Considering the complexity of the system I think OTR is reliable. What puzzles me is the loose alternator wires because as installed they are tight and then coated with a heavy sealant which would prevent them from coming loose. I suspect someone worked on the alternator and just failed to properly tighten and seal the terminals.

[jack14r]

Two months ago I had an alternator wire break,the factory crimp was not centered on the connector and the crimp almost cut the wire,over time with the vibration and heat the wire broke at the crimp,the dash light came on and I started the generator which charged the bus batteries,it was night and I was only 15 miles from home.I don't know how long the Guest charger will power the coach with headlights on but I doubt that it would supply enough current for several hours at night.I had a regulator fail last spring and I had to drive 3 hours and the Guest charger overheated after about 2 hours and shut down,I had another charger with me and hooked it up and made it home.

[Jon Wehrenberg]

Interesting that Liberty went with Guest.

I have the old converter and so did my first bus. They did a great job as backup. They are not recommended as continuous use devices to maintain the batteries as the Guest is.

[sticks]

Jon

Thanks for your input. Once my battery warning light came on and my OTR went out permanently I called Troy at Liberty. He said my alternator was not working and I should turn off headlights and blower motor to preserve chassis batteries. I did already have the generator turned on and the cruiseairs all on and the front shudders open. This helped for a while but the driver is still isolated from the front cruiseair.After about 15 minutes the front cruiseair stopped and it showed a " HI" PSI code for the remainder of the trip. That's when I lowered the toll window and recalled how we all use to drive down the highway with our windows down back in the " good ol' days"

[Jon Wehrenberg]

In case anybody has missed the ball breaking and the debates regarding OTR, Cruise Airs and roof mounted AC units here is the short version to help Stick understand what is happening.

OTR is the most powerful and easiest way to maintain comfortable temps inside our buses when traveling. It is over 80,000 BTU and there is no energy management on the part of the driver.

But in the absence of OTR the alternatives are Cruise Airs or Roof airs run through inverters (if set up that way) or the generator. Cruise Airs were what all coaches had when Prevost coaches were being converted in the 80s and some without OTR were equipped solely with Cruise Airs even after most converters went with roof airs. Cruise airs are strong, well built quiet units with the condenser portion mounted in the bays or behind the front bumper. But they do not function well if they are pulling air across the condenser from a highway that is radiating hot air. They are fine on a hot day when parked in the desert because the bus shades the ground below it where the air is drawn from.

So converters began using roof mounted AC units which draw cooler air across the condensers instead of the hot air rising off a highway baking in the sun. The only drawback to the roof units was complaints of excessive noise, some of which can be controlled by the installation.

Stick's Cruise Air quit and gave the error message because it was not getting enough cool air across the condenser coils. POG members with Cruise Airs have addressed this problem. Jim Shoen has added a pressure switch in the system and when pressures get too high he sprays a mist automatically across the coils. Someone else (maybe Steve Bennet?) has increased the air flow across the coils so there are ways to make Cruise Airs work while traveling, but they are not ideal.

[Devin W]

In case anybody has missed the ball breaking and the debates regarding OTR, Cruise Airs and roof mounted AC units here is the short version to help Stick understand what is happening.

OTR is the most powerful and easiest way to maintain comfortable temps inside our buses when traveling. It is over 80,000 BTU and there is no energy management on the part of the driver.

But in the absence of OTR the alternatives are Cruise Airs or Roof airs run through inverters (if set up that way) or the generator. Cruise Airs were what all coaches had when Prevost coaches were being converted in the 80s and some without OTR were equipped solely with Cruise Airs even after most converters went with roof airs. Cruise airs are strong, well built quiet units with the condenser portion mounted in the bays or behind the front bumper. But they do not function well if they are pulling air across the condenser from a highway that is radiating hot air. They are fine on a hot day when parked in the desert because the bus shades the ground below it where the air is drawn from.

So converters began using roof mounted AC units which draw cooler air across the condensers instead of the hot air rising off a highway baking in the sun. The only drawback to the roof units was complaints of excessive noise, some of which can be controlled by the installation.

Stick's Cruise Air quit and gave the error message because it was not getting enough cool air across the condenser coils. POG members with Cruise Airs have addressed this problem. Jim Shoen has added a pressure switch in the system and when pressures get too high he sprays a mist automatically across the coils. Someone else (maybe Steve Bennet?) has increased the air flow across the coils so there are ways to make Cruise Airs work while traveling, but they are not ideal.

Wow, what a great summary. I know what I have in our bus, but didn't really know what drove all of the initial specifications by the converter and the +/- 's of the choices they made. Having the cruise air units, I now understand what situations to avoid or make accommodation for.

[Jon Wehrenberg]

With respect to AC units for cooling our buses we all have to recognize almost any approach is a compromise and there is no perfect answer. Converters seem to have tried all possibilities. Some have used packaged 26,000 BTU units, others Cruise Airs, others roof airs and every choice has a cost in terms of applicability to a coach. While it is a lot of fun joking with each other about how good our respective systems work, the reality is that every installation has its strengths and weaknesses and we often only recognize the weaknesses when everything is already going wrong.

From an owner's perspective I would suggest doing "what if" scenarios so if something should fail that options regarding dealing with the failure have been considered and tried. If my OTR quits I can tell you I will not be planning on a cross country drive across the southwest in the summer because my Cruise Airs will not work either.

I would also suggest that in coaches with multiple AC units that instead of routinely using one or two that they all get used in rotation so if one has failed it will be known and steps can be taken to repair the unit. I found myself only using the front and rear AC units out of habit so now I intentionally switch around so all four of my Cruise Airs are used which will not allow the failure of one to be a surprise when I need it.

[phorner]

Good suggestion, Jon.

I found myself also using the forward and aft Cruisair's about 99% of the time and only used the mid coach units to supplement them if I needed additional cooling.

Now I try to intentionally "rotate" the use.

We are almost always in warm weather areas, so ours get a workout year round.

[JIM CHALOUPKA]

I would say use the ones most, whose filters are easiest to clean.

Further I would say that if you rotate the cruisair's use you will possibly wear them out all at the same time. Given the age of the owners in POG this could put their repair or replacement into a time when we would be too old to fix/replace them ourselves :eek:
It is better to use them individually and in the area that needs the cooling to best advantage and repair/replace them as the need comes up;)

If you turn your bus every couple years, then by all means rotate the use, that is, when it is warm in the front use the cruisair in the back and wear them out evenly and put the burden of replacing them onto the next/new owner.;)



:D

[Jon Wehrenberg]

I have found that on this coach I can access all filters with four screws each. Filter access is not so bad that I consider it an issue.

I intend to wear them out at the same time because I went through that with my original coach and did replace all Cruise Airs at the same time. I would much rather replace them all simultaneously when the first one pukes than wait and get piecemeal replacements. 15 years seems to be a good life span, and although we are close they are doing well.