HELP! Electrical Problem

[Fred Mc]

Today we left to go on a short camping trip and almost immediately the "no charge " lite came on indicating the batteries were not being charged. I thought at first the alternator quit but my voltmeter indicated the batteries were at 12.8 volts.  As I drove the voltage went down to 12.7, then 12.6. However when I dropped down a gear from 4 th to 3rd the engine  Rpm's increased and the voltmeter went up to almistv16 volts. Then when I shifted back to 4 th and the engine rpm's dropped the voltage would again sink to 12.7. I tried adjusting the regulator but it didn't make any difference. Any ideas for me to try,

We are camped for a few days so I would like to get it fixed. I don't like driving by the voltmeter.

Thx

Fred

[Fred Mc]

My bus is a gmpd4106

Regards

Fred

[Brassman]

Gear or belt driven alternator? Loose belts? Does the alternator have slip rings? Then maybe brushes. It could be a bad diode in the rectifier, or the regulator has gone t.u.. I'd replace the alternator and see if that works.
If it's a generator, then I would first look at the brushes.

[richard5933]

Have you tested the output at the alternator? Perhaps it's the regulator which has gone bad...

I've also learned that one of the first things to check is ground connections. Doesn't take very much crud to reduce the connection.

Lots of other simple things to check...

While you're checking, there are a number of cable connections between the alternator and the batteries. I believe my 4106 still carries the stock wiring setup, and the cable goes from alternator to starter and then to the batteries, not to the batteries directly. Be sure to block the suspension before crawling underneath to check these.

Richard

1964 PD4106-2412

[Dave5Cs]

If it is Belt driven alenso check your air adjustment on the belt tensioner. If you have an air leak and it is not tightening up the belts your rpm would change the tension and the output.

[Stormcloud]

I think your regulator is toast.  Charging at close to 16 volts isn't good for batteries. (speaking from experience here )

[Fred Mc]

It's a gear driven alternator(12 volts)
The fact that it still charges leads me to believe the alternator is not the culprit. In normal operation when you first start the engine the "no charge" light come on until you rev it up. Until it goes out there is no power to run the big heating/ac fan( not that I need or use that fan but just an observation). At one time I had an overcharging situation and was able to adjust the regulator but that doesn't seem to do anything now.

[Oonrahnjay]

I think your regulator is toast.  Charging at close to 16 volts isn't good for batteries. (speaking from experience here ) 

       That and the fact that the charge is going in and out -- both seem like a bad regulator (or bad connections/ground on the regulator) to me.

[bevans6]

If it has the original regulator it's a concoction of springs, levers, magnets and points, so it can and will fail after 50 years.  I would probably get a modern electronic replacement for it, or take it out, figure out how it works, make sure all the springs and points are good, and see what happens.  The other thing is if your setup has a delayed alternator start (you describe it not charging after a cold start until you rev it up) then it may have a field relay to control the field voltage to the alternator.  If it isn't working right, it might not let the alternator charge properly either.  Diodes usually work or don't work, they are rarely intermittent.  Bad grounds to the regulator are a known issue as well.

Brian

[Fred Mc]

I have ordered a new circuit board from luke . As the regulator is in the baggage compartment surrounded by holding tanks i may just have to remove them to get at it so maybe will move the regulator to a more accessible location at the same time. Up to now i just cut a hole in the battery compartment to be able to adjust the regulator. When i get home will have a good look at it. Too bad i didnt think of this 30 years ago when i did the conversion.

[Fred Mc]

Thanks Brian. What is involved in putting in a modern voltage regular.Im sure it can be as simple as disconnecting 3 wires on the old one and connecting them to the new one.

[bevans6]

Basically it will come pre-adjusted to a normal charging voltage, Should have battery, field and ground wires.  Battery senses the battery voltage compared to the set point charging voltage and tells it how much to charge, field is the output to the positive field terminal on the alternator, some have a negative fields connection as well, or the field coil is simply grounded at the alternator.  Ground is ground, simple.  Your alternator has three connections - large battery terminal is output to the battery. small connector is field coil, small connector probably strapped to ground is field coil ground, and then the last small connector is relay output.  So it's just connect the three wires and try it out, basically.

[Fred Mc]

So,would one buy an automotive one or truck or heavy duty?
The alternator puts out a LOT of amps.Or are they sized according to alternator output?

Thx

Fred

[richard5933]

You have to get one for the intended use. Definitely not automotive. If you don't have a source, start by calling Luke at US Coach.

Richard

1964 PD4106-2412

[TomC]

If it is a gear driven 50DN, most likely is the voltage regulator. I have a new digital voltage regulator on my bus. Instead of that big transistorized black box, the digital is about the size of a pack of cigarettes. Good Luck, TomC