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
My bus is a gmpd4106
Regards
Fred
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.
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
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.
I think your regulator is toast. Charging at close to 16 volts isn't good for batteries. (speaking from experience here ;) )
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.
Quote from: Stormcloud on September 12, 2017, 07:23:30 AMI 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.
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
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. ;D :(
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. ;D
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.
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
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
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
Thx Tom
Do you have a make or model or oart# or???
Well, I solved two of the 3 problems . An adjusdtment of the reverse solenoid linkage let me back up and a new Bendix Genenor let me air up.
BUT,
I still have the problem of the generator charging(or not charging the batteries)
I ordered a new circuit board from Luke but it still won't charge.
How can I test to see if the generator itself is putting out a charge?
Should I be able to get a voltage reading at the regulator?
One of the benefits of this exercise is that the voltage regular has now been moved from the baggage compartment to the old battery compartment so at least I can now get at it.
Its a GM PD4106 12 volt .
Thanks for any help
Regards
Fred
Have you tested the voltage at the sense terminal of the regulator? I had to replace my regulator several years ago, and they sent me a new solid state regulator. When I got it hooked up to the original wiring, it would fluctuate terribly. I ended up having to run a new wire for the sense terminal directly from the battery. Something in the original bus wiring was causing a problem with the sense voltage. When I connected directly to the battery, it was rock solid and has been for 11 years now!
I agree with checking the wiring to the regulator. If the regulator can't get a good reading on the batteries then it won't send a charge. Ditto on the ground wires.
When I had the interior out of mine and was able to look through the inspection/starter window I realized that there are battery cable posts all over the place. The factory setup apparently didn't use straight runs of cable, rather they used lots of shorter lengths joined at the posts. Check each of these for good connections. By check, I really mean take all the wire lugs off the post, clean with the abrasive cloth of your choice to show clean metal, and then put back together tightly. While you're there, you might want to inspect each and every battery cable lug to ensure that they are still tightly in place and show no corrosion. I've discovered that it's necessary to inspect thoroughly to catch corrosion on the inside of the lug, not just for the crusty kind on the outside that's easy to see.
Same for the places the ground wires mount to the body and to the engine. Get your hands on each of these and check them over.
More than one of mine looked fine from the outside. They were tight and I assumed things were okay. But, when I opened them I found a thin layer of corrosion between all the many layers - more than enough to stop electrical current from flowing. Once on my forklift I had a no-start situation. Terminals all looked great and were tight. When I took them off, I found that the positive terminal had a layer of build-up which can best be described as scale. Once it was removed things were problem free. Problem appeared suddenly, but probably had been building silently for some time without my knowledge (or permission.)
Remember - block the body of the bus well before getting under the back end to check all these connections.
Richard
As Craig says, check the 12v wiring to the regulator. When running, check the voltage on the field terminal, should be some voltage there. To check the alternator for a test, jumper 12 volts to the field terminal briefly, check the output voltage, should spike fairly high.
Brian
Success! Well maybe.
I discovered that the positive terminal on the regulator , which is connected directly to the battery was dead. So, when I jumpered it directly to the battery, it sounded like the generator was working as the engine speed slowed slightly and the "no charge" light on the dash went out and the voltmeter showed a voltage of 14.5 (note, I had adjusted the "pot" on the regulator previously so may have it set too high). Also when I put a test light on the field terminal of the regulator I got a pulsating light.
However, the a/c/heater motor would not come on (not that I need it)but this generally didn't come on until the "no charge" light went out.
Any comments?
Thanks
Fred
I also notice that when the engine is turned off there is a 3 amp draw from the regulatorvto the battery.
usually the no-charge light and the AC motor are controlled by the relay output of the alternator going to a control relay. The same relay controls both things. There should be virtually zero draw from the regulator when the engine is off, 3 amps is way too much. Maybe on your bus the stock setup controls the power to the regulator through a relay, so it only gets power when the engine is turned on, and you've bypassed that?
`The wiring diagram shows a direct connection from the battery to the pos term. of the regulator. When I checked that there was no reading at the regulator so I ran another wire from a hot terminal in the battery compartment. However I then can measure a constant draw even when the engine is shut off. And when I put a test light on the field terminate it constantly flashes.