Posted by Todd Wilson on Monday, September 17, 2007 at 11:30:41 :
In Reply to: 1975 dodge truck posted by Gene on Sunday, September 16, 2007 at 10:52:05 :
Double check your bulk head connector and make sure its plugged in and tight at the fire wall. Also make sure the connectors are not corroded. Its not so bad with the 70's trucks but on the older Mopar cars if you were a bigger guy and moved your foot or stretched a a little bit you could bump the inside portion of the bulkhead connector and pop part of it loose with your left foot/toe. Things would continue to run but the charging circuit stopped working. With the age of these vehicles its possible that plastic has cracked or the connection has come loose or corroded. Could be a bad wire. Check for a splice that has come loose or a pinched or exposed wire.
It also sounds to me like it could be bad diodes in the alternator itself. If thats the case its gonna be a very weak charge if any and you will slowly run your battery down even with the truck shut off over night.
The voltage regulator could also be bad. It may be a ground issue there but I would think it would be hit and miss on working and then not working.
I have seen both alts. and volt regs bad, new out of the box. Theres cheap ones and good ones and depending on the parts stores is what they sell.
A volt meter should help you determine whats what.
A bad alt or volt reg or the wires from the reg to alt are bad.
Here's the electrical on a 74.It should be the same for 75.
http://www.chargerfever.com/74truckelec.htm
Todd