| Engine starter will not energize without aux battery switch [message #357308] |
Tue, 28 July 2020 13:45  |
rgogan
Messages: 82
Registered: February 2004
Location: Milwaukee, WI
Karma: 0
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Just returned from a pleasant trip to Vermont to visit the family in my 1976 GMC mostly stock under the hood Eleganza.
After stopping for a freight train and turning engine off, starter would not turn engine over and New York drivers behind me were not holding back with their horns. No solenoid click, nothing. Flipped aux battery switch on and starter barely turned engine over and but it started.
Generator warning light was not glowing on the dash. Engine was running fine. Felt we might be looking at worn brushes on a starter motor since it didn't look like a generator failure. Decided to drive the rest of the way home to Milwaukee without shutting the engine down. The only starters available for the 455 were in New Jersey or Minneapolis and would not be available for several days.
Made it to 1AM on the toll road when the headlights and dash lights dimmed. Pulled into a service center and found the engine battery measured only 9.8 volts. Seemed obvious that the alternator was not charging the battery but how could we have driven for 12 hrs with a bad alternator on the battery alone? Anyway the alternator had failed 3 yrs ago and had been rebuilt that recently. Also why wasn't the generator dash warning light on letting me know the generator was bad?
Decided to get out the service manual and one of the first alternator checks to do after the proper function of the dash warning light is ascertained is to measure the voltage, with the engine off, between the generator +output to the battery and the ground. I had an 0 volts. Decided that I had a severed wire somewhere in the harness and took the ring compression connector off the generator (alternator) and found it was attached by only two strands of the 10-12 strands of wire in the 10 gauge conductor. Put a new compression ring connector on the newly stripped wire, charged the battery, started the engine, measured 13.5v at the battey and drove the rest of the way home.
I figured the generator failure light had not come on the dash because there was still a weak connection with a few strands of wire allowing limited generator output but it was not enough to charge the battery. This was an unusual failure mode and I wanted to share my experience with other GMCers so they might check this wire for possible failure.
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| Re: Engine starter will not energize without aux battery switch [message #357315 is a reply to message #357308] |
Tue, 28 July 2020 16:57  |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Bob,
Three things here:
First, I am glad that you were able to diagnose and correct that issue. Nice writeup.
Second, an (SI)vehicle that has few other demands can run a long time on the main engine starter battery. More than a few of us have put a jumper on the isolator and started the APU to support the house bank so we could get to a safe harbor.
Third, and entirely unrelated (I guess I haven't bothered you about this before), but this is a very helping and supportive group. We really like to know both who we are helping and what we are dealing with this time. To this end, would you please fill in a sigfile for us? To do this, go up to <Control Panel/Account Settings> then click on <Preferences>. There you will find a place to put in your name and a short about the coach including major mods and finally a geographic reference. This last is needed because apart from the obvious climate issues, this is an amazing helping and supportive community. That means that if the situation merits, you may have an experienced owner call (on) you to assist. With the experience base here, that is a power card to have in your hand. Oh, and when done, please scroll down to <Update> so it stays.
Glad you made it through New York safely, that place scares me these days.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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