Alternator/Regulator failure

I was on the road to Asheville,NC last week and the voltage began to fall on the dash gauge and the battery icon showed up on the dash,I knew that I had a Guest charger hooked up to the coach batteries and I cranked up the generator and the voltage came up to 25.5-26.I only had 25 miles to go so I continued to my destination,the strange thing is that neither the alternator or the regulator have any thermal protection but when it all cooled down it began to work again.Today I left Asheville and in about 30 minutes the same failure happened again,the Guest charger could maintain 25+ volts for about 1 hour but then it fell to 24 volts so I stopped and hooked up a 30 amp charger that I carry with me and made it home.Prevost says that there is no thermal protection so I am trying to figure out if this is a alternator or regulator failure.Prevost has recommended a bus shop nearby and the shop foreman is convinced that the regulator is the problem.How can I verify that the alternator is not at fault and it really is the regulator.This coach has the 270 amp alternator and the Delco regulator.

I replaced my regulator last year when the voltage started acting up. Fixed the problem. Mine went bad when I overcharged my batteries with the on board charger while plugged in.

Jack,

I am assuming the alternator you are talking about is the big one.

It is cooled via an oil bath. The rear of it, as seen from the RH side door is actually an oil chamber that bathes the diodes. If you suspect it is shutting down due to heat(?) the oil supply line can be removed and you can check the flow by starting the engine. Do a rear start and rig up a way to catch the oil. If you suspect the alternator will have a high output in amps when you run this test, remove the field wire so it does not try to charge with no oil cooling. Any output in excess of 100 amps without oil cooling will damage the diodes.

The return line is the big line coming out the center bottom of the alternator.

The only way I can imagine heat being an issue, assuming the oil supply is adequate (there is a spec that I think I can find if needed) is if the alternator is really working hard, such as to charge dead batteries, or if you are pulling heavy loads off the inverters.

As to the regulator, I can't figure how it would get hot. All it does is sense the battery voltage, and open or close the circuit supplying 24V to the alternator field. The regulator is in the simplest of terms a switch that opens when the voltage reaches a specific point, like 28 volts, and then closes when the voltage drops below that voltage. All that switch is doing is limiting the voltage output of the alternator by removing power to the field. If it did not do that the alternator output voltage would go far beyond 28 volts.

We had a very similar problem last summer.

The chassis charging voltage would drop, and the dash indicator light would come on, when starting out on our travel for the day. Would not usually stay on, but would occasionally happen.

Anyway, with Jon's invaluable help, I made a diagnosis of a bad regulator, which is what we had suspected.

Sounds like your charging problem, and any "warming" may be just coincidental.

I would suspect the regulator first..... but I have no idea why you weren't able to resolve it temporarily by running the generator with the charger running. That was always my "back-up" plan....

Quote:

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Originally Posted by garyde

I replaced my regulator last year when the voltage started acting up. Fixed the problem. Mine went bad when I overcharged my batteries with the on board charger while plugged in.

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Gary, I don't understand. Tell me more, please.

Jon,I don't believe that the oil is not flowing because it would have opened the diodes and the alternator would not have ever charged again.Paul the charger is only ten amps at 24 volts and it was adequate until I had to turn on the wipers and then the voltage began to drop.I will check it this afternoon and try to get it to fail and check the field voltage.

I don't envy you chasing an intermittent problem Jack. It still could be a bad alternator although it sounds as if the regulator is the real culprit.

When the alternator gets hot it could be an issue relating to the slight dimensional change of things when it is hot, but my first guess would be the regulator. iF you suspect heat nothing saus it has to be re-installed in the engine area if you can find a cooler place. Just lengthen the wires.

I verified that it is the regulator,I ran the system with a large load and it finally shut down,then I jumped from the field post on the regulator to the battery post on the regulator and the alternator put out 33 volts which would be the unregulated voltage at hi idle.I am going to take it to a shop that Prevost recommended tomorrow morning,I will report back on how things go there.

Changing out that regulator was a pretty simple job on our bus. I was able to order a replacement from a local auto electric shop and have it the next day.

If yours is as accessible as ours, you probably can do it yourself easily.

Its in warranty,I bet it would be cheaper to buy it than the fuel to drive to have it replaced,but I want to visit the place for possible future maintenance.It might take 10 minutes to change it out,the regulator must be the weak link,from talking to the service people they replace them on a regular basis.

Quote:

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Originally Posted by jack14r

Its in warranty,I bet it would be cheaper to buy it than the fuel to drive to have it replaced,but I want to visit the place for possible future maintenance.It might take 10 minutes to change it out,the regulator must be the weak link,from talking to the service people they replace them on a regular basis.

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Jack, sorry to hear you are having problems with the coach. Sounds like you have located the issue.

I wish you would have sent us a note letting us know that you were attending the Lions Club Horse Show?? The NC Ag center is only about a 45 minute drive from our farm. Sorry we missed you and please do let us know when you will be in the area again. The Blue Ridge Show perhaps? Our granddaughter (only 10) showed in two Academy classes in Arden earlier this month and won them both! Needless to say she was a happy little girl.

Debi and Bob-05

Jack, I called Prevost and got a regulator sent to my house 2nd day air. About $180.00 for the regulator I believe.
Jim, from what I remember, I turned my on board charger on one afternoon and walked away. The next day I discovered I had boiled my batteries.
Refilled the cells. Started the engine and the voltage was low. While driving, I ran the charger to attempt to maintain voltage.
So, somehow I blew the regulator. It may have been a surge when starting with bad batteries, or from charging too long while boiling my batteries.

I don't know when Prevost made the switch to the current regulator. I still have the old cast metal housing regulator.

When my alternator died I considered replacing both, but in the last few years a number of owners have had failures of the new style and I am not sure in this case that new is better.

The old style regulator is still available, and for those who wish to get up close and personal the internals are also available for repairing rather than replacing.

I would consider giving John Kincaid john.kincaid@volvo.com a call at Jacksonville Prevost. John is the service manager in Jax, really great guy and will go the extra mile to help his customers. he has been great to me and always gets things done.

John Kincaid
Prevost Jacksonville
Service Manager
800-874-7740 phone
904-886-0092 fax
john.kincaid@volvo.com

I had a appointment with Burke Christian Tours in Maiden,NC and they were great.The service manager is Sonny and the technician was Dave(I knew him from Featherlite in Mocksville,NC).As I said it should be a ten minute job and it was except we talked for awhile about coaches etc.They have 38 Prevost seated coaches and several larger vans that they use for tours.The billing office will submit the paperwork and defective part to Prevost and they should send me a check because I actually paid for the part and labor.Dave is a great resource for me because he is in NC and has worked on almost every brand of coach,he did quite a lot of work on my Marathon when he was at Featherlite a few years ago.I would recommend them to any coach owner,just make sure that you have the directions or a good GPS,they are a little off the beaten path.

Jack,

I have had work done on my old coach at Holiday Tours in Randleman. Marzel is the gate keeper and a nice person to deal with. David is the shop foreman. They do good work and I would not hesitate to take my coach back any time I need maintenance work that I can't do myself - which leaves lots of room for return trips. Their hourly rate is exceptional as well. I am allowed to remain with the coach, go down in the pit and take a look for myself. Almost like going to Bus College!

Randleman is just down US 220 from Greensboro. Easy in and out. The bus driveway is the second driveway. I used the first driveway and they still didn't get upset with me.

Hope you get your problem corrected without too much headache.

We just made a 3000 mile trip and had to buy 6 new chassie batteries. They seem to be over charge, swelled up, but 12 volt guage was only showing a little over 12 volts and 24 was about 26. My husband read in book to check equalizer to reset, but can't find resets they are talking about. He has read posts here and is going to see if can test regulator. 91 Liberty. Thanks in advance for any, as there were hidden costs on this trip. Did see 2 nice Prevosts, 1 around Canmore Alberta and 1 in B.C.
Judi Brown
Oh all most forgot, Can any one tell us where these resets are.

Hi Judy. With a voltmeter test your Vanner and your Alternator regulator.

Judi,

I think there is information on the POG home page about electrical systems and it tells how to trouble shoot electrical stuff like alternators, regulators and equalizers.

Before you buy batteries or get any age on a new set you want to be sure everything is working or you can convert a set of batteries into junk.

As to the reset on equalizers, going by memory here, at one time the Vanner equalizers did not have a circuit breaker on them. Around your vintage or maybe a little later they began installing resetable breakers in the bottom of the equalizer. If it tripped it could be reset. It was located about the center bottom of the equalizer.

Your batteries should read a lot of voltages depending on whether they are being charged, at rest with no loads or at rest with loads. Also you likely have multiple ways to charge the batteries such as the engine driven alternator, converters or inverters depending on how your coach was set up, and maybe a built in battery charger. All of those items need to be checked. It is no big deal but important.

If you are coming to OKC I think Skiffer may have the electrical systems seminar on the agenda.

Thanks Jon.
We are not putting in any new batteries till find problem. The $800.00 in
new ones to get home are toast. The green light on dash stays on and he
says he noticed when running lights were on it dropped below 12 volts. Are there 2 alternators on there, 1 for 12 and 1 for 24 volt . The reason I ask
we had a MCI and it was at the back of the motor and the Prevost has 1 at the front right side and is not oil cooled, Haven't looked at back yet.
Again thanks for any help.
Judi Brown

Jon
One more thing. the former owner added 28 extra running lights and the same for signal lights and my husband thinks that is 2 heavy of a draw and was wondering if he just took bulbs out of them, would that reduce draw. Can't take off or would notice on paint job. When LED's drop in price replace.
Thanks
Judi Brown

We found the resets the book was talking about,they were behind the 12 and 24 switchs. That draw pulled out after pulling release button in engine compartment. So are going to get bus runnig and see if charging right.
Thanks
Judi

Judi,

28 extra lights will not create the problems you describe, however it is important to understand your electrical system to properly point to the source of your problem.

For example, at one time the Prevost headlights and the ATEC and DDEC computers were the 12 volt items on the Prevost side of your electric system, with the balance of the lighting being 24 volt. The change to 12 volt lighting for the whole coach was made at some point which obviously added 12 volt loads meaning the equalizer(s) had to be working right or in a relatively short time the batteries on the 12 volt side were drawn down. Clearly this means an understanding of the Prevost electrical loads is important so you know where to focus when trouble shooting.

If the 12 volt Prevost electrical system voltage drops to a certain level, you not only have dead batteries, your computers for DDEC and ATEC shut down and your bus is not moving.

Keep in mind that the house and the bus electrical systems are isolated from one another so you do not get confused when trouble shooting. From your post is sounds like the house is 12 volts and has its own alternator. That makes the trouble shooting much easier because you are not dealing with an isolator and the alternator is not supplying two separate systems. I don't know what the practice was for Liberty at that time. It is possible the alternator mounted on the rear of the engine out of sight is a 12 volt, 270 amp for the house, and the smaller alternator is a 24 volt of lesser amperage, such as 145 amps is dedicated to the bus. Or not. You need to determine which is which because I can see if the small alternator is for the bus 24 volt charging, and you run all lights plus the OTR air conditioning the batteries may discharge.

My guess is that if the running lights pulled down the voltage on the 12 volt side of the Prevost system the equalizer is likely the culprit and if you found and reset the equalizer circuit breaker you may have solved the problem. The equalizer(s) when checked with a voltmeter should read 24 to 28 volts on the 24 volt electrical post and half of that on the 12 volt post with an allowable 1/2 volt variation. If you do not get those values the equalizer is not functioning properly. You may have one 100 amp equalizer or 2 50 amp equalizers. The voltage variations will be dependent upon whether the engine is running when you do the test or whether it is not and the batteries have been drawn down. Engine running I would expect to see 27.4 to 28.2 volts, or engine off, fully charged batteries 25.4 to 25.7 volts, with the values at the 12 volt posts (batteries or equalizers) half of those voltages.

Thanks to everyone for the help. Husband thinks has problem licked amd managed to save new batteries. We had computer on trip,but I couldn't
remember pass word, his computer not mine, so another lesson learned.
But 800.00 poorer.
Judi B