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.
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.
