| Re: Alternator [message #312478 is a reply to message #312455] |
Tue, 24 January 2017 20:03   |
 |
Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma:
|
Senior Member |
|
|
Russell K. wrote on Tue, 24 January 2017 15:52When we bought our '78 GMC Eleganza II this past August, it came with decent maintenance and repair records back to 1983. I was digging through the documentation again last night to see when the alternator was last replaced, and could not find any record of a new alternator. According to the voltmeter in the dash, the alternator is putting out about 13.5 volts under load with the lights on. Could this actually be the original alternator? (see pics below) I could not find a part number or model number on the current alternator. If it is original, does someone have a current part number and recommended brand for a replacement? I think the alternator is charging the house batteries as well as the chassis battery. Do I need to go with the 100 amp alternator, or an 80 amp?
Thanks again for the help.
Russell
Russel,
You are obviously not stupid, but you don't seem to have looked at the whole picture. 13.5V out of the alternator is just fine, under many circumstances, but you gave us no hint as to the conditions. Obviously the engine is running, but how long since cranking and how much did the voltage rise as soon as the engine was at idle speed. All this stuff matters. Right now, I'm with those that say leave it alone.
Easy test for any automotive charging systems:
Log the rest terminal voltage. This should be close to 12.5.
When you crank, the terminal should not drop below 10.5. If it does, you have a battery problem.
As soon as the engine is at a stable idle, the terminal should have gone up "about a volt".
Turn one the headlights and the heater blower on. The the terminal stay up? Good the regulator is good.
What happens after that is very situation dependent.
So, unless you have nothing better to do, LEAVE it ALONE.
You don't know me (something many might be thankful for), but I know this stuff.
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
|
|
|
|
GMCforum
Search
Help
Register
Login
Home
