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voltage regulator problem

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voltage regulator problem
Thu Jul 09, 2009 12:33 pm

I am having a problem with the charging system on my 1988 eagle 15 . The voltage fluctuates from under charg to over charge on the gauge, about 10volts to 15volts giving all the lights a flashing appearance. The manual that I have does not address this problem. Has any one experanced this? maybe could send me in the right direction. Thanks, Ray
Ray Sell
1964 Eagle 01
8v71 4 Speed Manual
1988 Eagle 15
8v92T 740 Allison
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Re: voltage regulator problem
Thu Jul 09, 2009 2:21 pm

Hello Ray,
did you install some new electric user? dos it the same when you have all electric users on (light, beam, van....)?
Are you sure, all your batteries are working good?

The AC Generator/Alternator creat electric between 14 - 17v. If the regulator is broken, it can make + or - till 10v. The electric wave needs to get regulatet for give constant the same 13.6v out, if you need electric or not.
If your Batteries are ok and no new Toy installed, than i would look at the regulator. You can messure the in and out electric and find out if it is the same.

hope it helps
Pesche & Nats
Interlaken Switzerland

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Engine Volvo B10 1989
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Re: voltage regulator problem
Thu Jul 09, 2009 2:32 pm

Twoeagles, Another thing you can check ,if the regulator is constant ,is the sending unit in the electral box in the engine compartment to the dash gage. Mine was going from 5 to 14 volts, then it went to zero.I checked the voltage going to the Batt.,then the sending unit. I replaced it and that corrected the problem.
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Re: voltage regulator problem
Thu Jul 09, 2009 7:30 pm

Ray, I can't help you with this one, but just wanted to say, I'm glad to see you are working on your new baby! These guys will get you headed in the right direction.

Becky & Paul Lawry
1968 Eagle 01 #7443
Silver 8V92 HT 740

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Re: voltage regulator problem
Thu Jul 09, 2009 10:25 pm


Coincidentally, I also have an '88 Model 15 (formerly a Trailways then 'Hound). We experienced the same problem when we first had the bus. Basically, the voltage was oscillating between 12-14 volts with the lights doing the same thing.

After doing a little diagnosis, I found a three wire relay (like an old Ford horn or starter relay) that was wired in-line between the alternator and regulator. One of the poles was significantly corroded, and when I cleaned the pole (can't remember which one), it worked fine. It had a Delco long part number (7 digit something like 1118751); I replaced that relay and it worked fine.

The relay was located in the left rear corner panel not too far from the voltage regulator.

Good luck,

Art Wales
1988 Eagle 15
Riverside County, CA
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Re: voltage regulator problem
Sat Aug 01, 2009 10:31 am

I too am having the same problem, If i don't get this problem solved.
I am just going to put a 130 amp AC DELCO self energized alternator on the bus, if your not using the bus air u can do it. I just am going to have to manufacture a bracket and the belt will be driving off the harmonic imbalancer. I have seen this on another bus and it is doing great!
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Re: voltage regulator problem
Sat Aug 01, 2009 11:11 am

Ahoy, Ray,

Below is a post I put on the bus conversion bb in March for my (12vdc) regulator(s).
May be of help to you. I still have a couple of them.

Enjoy /s/ Bob

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« Reply #3 on: March 28, 2009, 03:10:16 AM » Quote Modify Remove

Ahoy, Tom,

The regulators are Delco Remy 9000551
Pretty much the 'standard' item to control those big old alternators.
One of these came from my -01 Eagle, controlling a ~~250 amp air cooled alternator.
The others from GM's, controlling the big oil cooled alternators.

I'm surprised that these have not been snapped up at only $50.00 each by you busguys.
The older buses many of you drive almost certainly have one of these aboard.
They are so reliable that you probably don't even know where it is.
If it quits, you will have a problem finding anyone in an electric shop who even knows what it is that you want.
Then, when you find one, you will discover how very valuable the shop believes it to be.

Enjoy /s/ Bob email
Bob Belter Carmel CA ---- Eagle -01 /w/ Cummins M-11/ Roadranger ten speed RTO1110
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Re: voltage regulator problem
Sat Aug 01, 2009 1:23 pm

If you have the regulator for my 1988 15 please let me know i need one you can email me or call me at (912) 288-4612
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Re: voltage regulator problem
Sun Aug 02, 2009 9:16 am

When you have voltage swings as described, you also have to consider a circuit breaker doing its job. Could be you have an overload condition on a circuit that is causing the circuit breaker to open, cool off and reclose, only to open again due to high current. If the "overload current" is severe enough, it can cause the voltage drop and give the appearance of a regulator problem. If that is the case, you should be able to hear the breaker clicking as it opens and closes. Might save a heap of money on replacing regulators or alternators/generators.
1978 05 Eagle with 450HP Cummins ISM / Allison HT740
Started in 1996 and still an in-progress hobby.
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Re: voltage regulator problem
Sun Aug 02, 2009 11:06 am

A bad diode in the alternator will also cause that problem .
I just changed one in mine to correct the very same problem.

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