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RV voltage regulator problems.

85 holiday rambler, Chevy 454...

85 holiday rambler, Chevy 454, batteries are not charging just had alternator and regulator checked and in working order. I put two new 12 volt batteries in and same thing. Starts at 12 volts and goes down slowly as the RV runs. Lost power to all the dash functions (the fans, back-up camera, windshield wipers, etc.)

What is the next step? It’s my parents RV and trying to save them money and fix it for them.

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Answered in 4 minutes by:
7/23/2011
Michael Reush
Michael Reush, RV Technician
Category: RV
Satisfied Customers: 3,249
Experience: Serving the rv industry since 1977
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We need to follow the voltage; do you have a volt meter? On the motorhome, the alternator goes to a ‘isolator’ that splits the charge to both sets of batteries when it’s running. This can be one of two different units. Here are pictures of both. Locate them by tracing the cable from either set of batteries, then when running check for a charge voltage from the alternator, then a charge voltage to each set of batteries. We will deal with the draw on the battery that is causing it to decrease in voltage once we have checked the charging capability.

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Customer reply replied 6 years ago

I am not at my parents. I just found the isolator this morning and have not checked the voltage. I do have a multi-meter to check the voltage but need info on how to do it.

I see I left out the photos, however, you have located it and that’s a great start. With the volt ohm meter det on DC voltage, ground the black probe on the engine or something metal – then touch the isolator wires and take a reading. Is it the big square one or the round one?graphicgraphic

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Customer reply replied 6 years ago

This RV has two round solenoids in the engine compartment and the square isolator in a small compartment with relays. If I do the isolator what are the volts that I should be getting?

First of all, check the voltage of the batteries, and take note of it. Then at the isolator, when the engine is running we are looking for a charge voltage and again it depends on the voltage at the batteries. If the batteries are fully charged and reading 12+ volts, you should see 13.5 +- volts.

Michael Reush
Michael Reush, RV Technician
Category: RV
Satisfied Customers: 3,249
Experience: Serving the rv industry since 1977
Verified
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Customer reply replied 6 years ago

Thanks!

I will check this out and may get back on line Sunday for more info.

I will be here for you when you’re ready to get back to me. I'll be here then or shortly thereafter.

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Customer reply replied 6 years ago

Checked voltage this morning on camper.

Center post 0-volts post 1&2 have 12.4 volts with RV not running. When I start RV up and let it run I have the same readings at the isolator.

I had the alternator and regulator checked and it was good. I must be missing something simple here.

Thanks

Hi, thanks for getting back to me. The alternator is not sending a signal to the isolator. Somehow that wire is not connected. Which one of the isolators do you have? The square one has the wire from the alt directly to it, the round one simply has the engine battery connected to one side (with the charge line factory installed) so you would see the charge voltage there. Do you see it at the engine battery (the charge battery)?

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Customer reply replied 6 years ago

I am checking at the square one. I have two round ones in the motor compartment. I know that one should be the starter solenoid and I thought the other one is the back-up starter solenoid. The one has more wires attached than the other.

For now, disregard those other ones and let’s focus on the square one. This is the ‘charging component’. If you are certain there is no charge voltage at the center post of the three, take a jumper wire from the output of the alt to it. Question: are you seeing a charge voltage at the alternator output lug?

graphic

Yours is different, but it will have the 'red' connection this is the output.

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Customer reply replied 6 years ago

No, I used the multimeter and put the black on ground and red on the red cable from the alternator and had nothing.

“Just had alternator and regulator checked and in working order” – Something is different.

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Customer reply replied 6 years ago

I am puzzled about it too. The amp gauge is showing that there is a charge of less than 12 volts but that there is a charge and it slowly goes down as it runs.

Disregard the amp gauge, as you are right there at the alternator doing the test, and just know, we will stay at this as long as it takes. Did you take the alternator to the auto parts store to have them check it? If not, I would do so at this time.

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Customer reply replied 6 years ago
I took it to a gentleman who does starter and alternator repair. He put the alt. on the machine and put it under a load and it checked out. It's a 105 amp alt. with external voltage regulator. I took the regulator off and back to him and it checked out.

The question is of course, why isn’t it working now?

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Customer reply replied 6 years ago

He told me that he would do a different ground wire on the regulator because it just had a little screw and nut attached to the case. I put the ground wire to the bolt that attached the reg. to the RV (self-threading screw) to the frame.

Do you have a wiring diagram for your unit?

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Customer reply replied 6 years ago

I will do some more checking and get back to you on Tuesday. I have full day on Monday's and won't have a chance to get back with you.

Thanks again!

That’s fine, I'll talk to you then. I'll see if I can get a wiring diagram for you. Click here there is some interesting reading.

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Customer reply replied 6 years ago

Thanks for your time and info!!!

I just got everything working including the fans and misc. items on the dash. It was a two-part problem that involved the ign. switch and voltage regulator.

There was no current from the ignition switch to the regulator, so it did not start the field wire to the alternator. I pulled on the socket to the ignition switch and fans turned on an so on. I tested the regulator according to RV manual and still was not getting a field voltage to the alternator. Went to local parts house and told them I needed voltage regulator for a ford style system and put it on and after pushing on the connectors a couple of times, I heard the alternator when it kicked in.

I have voltage and all the misc. items are working for now!

Thanks for your time and help again, will be back in touch as there are still some minor issues but they can at least get on the road.

Excellent, excellent I knew you could do it. I'll be here if you need any more assistance.

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