Too much power from alternator when engine running

[76PRROW]

I have slowly but surely revived the power systems in the coach, but I am just completely confused at the inconsistent information I have gathered from the charging system when the engine is running.

On the first drive home when it got dark I had to use my headlights. After a mile or two they got very dim and the engine died. I had to get a jump start to get off the street. I assumed this was because the alternator was bad.

However I have been doing extensive testing with my multimeter to test the house battery system. I am using an extra car battery to act as a house battery just to test the systems. I will purchase 2 golf cart batteries when I can afford them.

I start the engine every other day so I can be sure im not stranded. Today when I started it I decided to get the multimeter out to test the engines alternator and to see if power is being given to the house battery.

When I first tested the house battery leads I got a reading of 15.7!!! I was not expecting that. I then tested the starting battery voltage and it was at 15.9!!!

I read online that this is "acceptable" for an alternator to charge that high. But here is the problem. With the engine running I began to test some electrical stuff in the coach. I tried the roof air circulation fan and it was running faster than I have ever seen it run. Same with the water pump. This was obviously more power than even on shore power. When I went to try a lightbulb in the bedroom it immediately burned out. Later I found out I left a light on in the bathroom and it had also burned out. The battery meter also went past the full indicator. This was with just idling the engine.

I think the voltage regulator might be bad but shouldn't there be fuses blowing before lights blow out?

And why did the battery die on the first drive home if there was plenty of charging going on?

[1990HR]

Sounds like both your voltage regulator is bad (Over charging) and the alternator's coil insulation is bad.
When a stator or alternator is charging it produces heat. While cold they will charge but after they get hot current follows the past of least resistance which would be ground, back to it's source.
I have seen charging systems work fine cold but while at running temperatures break down and voltage goes to ground, back to source, not to the battery many many times.
Alternators are so cheap now, I would just replace it and not rebuild it.

[MotorPro]

Yes change the regulator. No it should not blow a fuse. Fuses blow from high amperage, high voltage actually lowers amperage.

[PwrWgnWalt]

Had a similar issue on mine when I got it - over 16 volts coming in when running!  Turned out to be the Voltage Regulator (VR), but was inconsistent.  A few bucks and a few minutes later, problem solved.  I might recommend starting with the easiest & cheapest thing first. Also, make sure your grounds (negative cables) are all good and clean/tight, including a ground strap from engine to chassis.


Not sure, but I "may" have run my engine while plugged into shore power... which could have led to the demise of the VR, but luckily it didn't zap the alternator.  The way mine was wired then (old style, finned, diode-type battery isolator) it probably saved the alternator.  Yours may not have the same limitation, but then again, it might.

[joev]

had same problem last year changed voltage regulator didn't fix it bought new alternator for $66 presto fixed

[DaveVA78Chieftain]

Based on the electrical wiring diagram on pdf page 18 of the 1976 Pace Arrow owners manual, make sure both solenoids are working properly.  I would disconnect the cross connects (both solenoids) first to seperate the chassis and house systems to make sure nothing on the house side is causing the chassis side to think it need to output a higher voltage.

Dave