Community Forums

4Knights · 08-16-2019, 05:12 PM

Hi folks! Long time since I’ve been on here. Missed ya. Life kids etc...
so the issue I’m hoping someone can help with :
Engine starts and runs but volts only show 9-10.5 max. It used to only run until battery drained then die. I changed out auto charge solenoid and now it will stay running but not put out more power than stated above. Alternator tests fine at parts store but won’t push more volts that show? No one seems to have an answer. One mechanic said it was voltage regulator but had no idea where it would be. Any thoughts?
Thanks in advance.
Ron

twinboat · 08-16-2019, 05:53 PM

Look for a battery isolator. If its bad, no charge gets thru.

Looks like this. Can be tested with a diode tester on a multi meted

Click image for larger version

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4Knights · 08-16-2019, 06:08 PM

Quote:

Originally Posted by twinboat

Look for a battery isolator. If its bad, no charge gets thru.

Looks like this. Can be tested with a diode tester on a multi meted

Attachment 257104

Thank you
Where would this device most likely be found? Under dash, in engine compartment?

twinboat · 08-16-2019, 07:28 PM

I'm not sure of its location. It should be in a battery distribution area.

Soppy · 08-16-2019, 07:55 PM

Measure the voltage on the large + terminal of the alternator. You should have battery voltage with the engine off and it should go over 14 volts with the engine running. The problem could also be with one of the small wires connected to the alternator. Some require a voltage from the ignition switch to start charging.

153stars · 08-17-2019, 06:46 AM

The voltage regulator should be internal to the alternator and tested at the parts store.To take battery isolator out of circuit you could move alt. & chassis batt. cables to same lug. Have you recently removed batteries and missed a cable or wire from it.

House Husband · 08-17-2019, 05:08 PM

Those diode isolators are a thing of the past. You coach has a RV Custom Products Battery Control center. Black box, under the hood. The isolator relay is in the box. No matter which chassis manufacture you have, the voltage regulator is part of the alternator.

Camping1 · 08-17-2019, 05:10 PM

You need to check the alternator fuse which most likely is located in the battery compartment, this is usually a 10A fuse, I had the same problem some time ago and went through replacing / rebuilding alternator, replacing batteries, sending my RV to a dealer etc at a cost of $960.00 only to find out that a 95 cent fuse was the culprit...! I was not impressed.

4Knights · 08-17-2019, 05:15 PM

Quote:

Originally Posted by House Husband

Those diode isolators are a thing of the past. You coach has a RV Custom Products Battery Control center. Black box, under the hood. The isolator relay is in the box. No matter which chassis manufacture you have, the voltage regulator is part of the alternator.

Yes the box on drivers side in engine compartment- I replaced that solenoid. Still no voltage above 10 when engine running.

Quote:

Originally Posted by 153stars

The voltage regulator should be internal to the alternator and tested at the parts store.To take battery isolator out of circuit you could move alt. & chassis batt. cables to same lug. Have you recently removed batteries and missed a cable or wire from it.

no, haven’t changed batteries in 5 years

Quote:

Originally Posted by Soppy

Measure the voltage on the large + terminal of the alternator. You should have battery voltage with the engine off and it should go over 14 volts with the engine running. The problem could also be with one of the small wires connected to the alternator. Some require a voltage from the ignition switch to start charging.

I get no more than 10 volts when engine running

Soppy · 08-18-2019, 05:36 AM

Do you have voltage at the alternator when the engine is not running ? You could try revving the engine up to around 3000 rpm to see if it starts charging. The only other thing left is the plug on the alternator and the wiring to the ignition switch. Some alternators us a sensing wire that needs to be connected to the battery before it will work. A couple of pictures would be nice. Make sure the belt is tight.

leadman · 08-18-2019, 06:47 AM

There were some GM alternators in your time frame that had an additional wire going to the alternator and there were problems with the plug on it. These also required a special aftermarket isolator that had a hot wire going to this wire on the alternator.
Also have you had your batteries tested. Five years old is about the time when most of them give up here in Az.
When I bought our current coach a couple of years ago the starting battery read about 10 volts yet it still started the engine. Gotta love gear reduction starters.