Author Topic: Wiring Changes to GMPD4106  (Read 568 times)

Offline Fred Mc

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Wiring Changes to GMPD4106
« on: October 24, 2017, 03:10:33 PM »
A month or two ago my bus quit charging the batteries properly.At first I thought it was the voltage regulator so ordered  an upgrade kit from Luke. That didn't work properly so I then  traced it to the Regulator Sensing Relay(I thought). So I ordered another one from Luke but it wasn't the problem either.

In the meantime I ordered two manuals that show how to replace the Regulator Sensing Relay with a magnetic switch and the other one how to replace the Generator Starter control relay also with a magnetic switch..

After spending a couple of days moving the voltage regulator and sensing relay from inside the baggage compartment (where I had put holding tanks 30 years ago) to the old battery compartment I discovered that it still didn't solve the problem BECAUSE the change would ONLY work with a different model number  voltage regulator than what I had (should have read the instructions better).

Further sleuthing led me to the Generator Starter control relay. The manual I had shows how to replace it with a magnetic switch as well. It basically involves replacing the relay with the magnetic switch and moving some wires to allow the blower motor relay (and Regulator sensing relay  to be energized from the driver's master switch. It wasn't really difficult but did require studying the wiring diagram to realize what changes were taking place.  You do loose the lockout capability so the starter can't be engaged while the motor is running but that hasn't been a problem with me in over 50 years of driving so I think I'm ok.

Anyway if you exclude the parts I bought that I didn't need the replacement is cheap($25.)

Offline chessie4905

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Re: Wiring Changes to GMPD4106
« Reply #1 on: October 24, 2017, 04:47:16 PM »
There's nothing like having the wiring diagrams when you have electrical issues. Good job!
GMC h8h 649#028 (4905)

Offline silversport

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Re: Wiring Changes to GMPD4106
« Reply #2 on: October 25, 2017, 09:06:25 PM »
when rewiring my 4106 my regulator did not work, come to find out that the supplemental book has a different regulator  and it is wired differently. after rewiring per supplemental diagram work as it should.  The strange thing is there is no difference in the two regulators.