Alternator Regulator
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Joined: Jul 2003
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Alternator Regulator
I have a 79 Ranchero w/351 that I've replaced the Alternator and Regulator on 3 times. Each time the mechanic said that output and wiring are within normal specified amperages or volts. Well this time the truck ran for about 45 minutes and died just like it did the last two times. The only other thing that may indicate a problem is that the dash lights aren't very bright. I asked the auto electric guy about that and he said the printed circuit board on the instrument cluster for the late seventies models constantly crack and can cause the dash lights to be a problem but that it wouldn't affect the charging system. I'm running out of options and patience with the car and it really is a great runner when it's running. Any idea's?
Logistics Pro
Joined: Jan 2002
Posts: 3,733
Likes: 38
Alternator Regulator
Millions of alternators and regulators sold every year, only to find later that the battery was toast. Lead acid batterys do not last as long as folks think and will show 12 vdc when they are not very strong amp wise.
Additionally many, many electrical problems can usually be traced to POOR grounds.
It is not probable to get THREE BAD alternators in a row (possible if the same rebuild shop has idiots) I hope you buy auto zone or some other lifetime warrenty parts.
Get the battery checked, replace with a new one if marginal. Insure your ground from the battery is clean and to bare metal (no rust or corrosion) on the frame or engine. If the ground goes to the engine , find the corroded or broken ground braid that goes to the frame and replace it. NO such thing as too many grounds!
Check the battery hot cable that goes to the starter to see that it is not shorted to the headers, frame or any thing other than the starter terminal. If it is a wimpy thin old style stiff copper stranded long cable, replace it whin a newer better made relpacement. Same with the alternator cable to the batery, get rid of all the old crap.
A vehicle of that age could use a good electrical cleaning. You should remove and clean all the terminals and connections that you can easily get to with out breaking into the back of the different components. I usually pull all the fuses, disconnect the battery and use a spray contact cleaner to get the system bact to good contact. I also replace the old flasher unit while under the dash. Pull and clean the headlight terminals, pull the turn sig and brake light bulbs and clean the sockets up. Make sure battery is DISCONECTED!
Additionally many, many electrical problems can usually be traced to POOR grounds.
It is not probable to get THREE BAD alternators in a row (possible if the same rebuild shop has idiots) I hope you buy auto zone or some other lifetime warrenty parts.
Get the battery checked, replace with a new one if marginal. Insure your ground from the battery is clean and to bare metal (no rust or corrosion) on the frame or engine. If the ground goes to the engine , find the corroded or broken ground braid that goes to the frame and replace it. NO such thing as too many grounds!
Check the battery hot cable that goes to the starter to see that it is not shorted to the headers, frame or any thing other than the starter terminal. If it is a wimpy thin old style stiff copper stranded long cable, replace it whin a newer better made relpacement. Same with the alternator cable to the batery, get rid of all the old crap.
A vehicle of that age could use a good electrical cleaning. You should remove and clean all the terminals and connections that you can easily get to with out breaking into the back of the different components. I usually pull all the fuses, disconnect the battery and use a spray contact cleaner to get the system bact to good contact. I also replace the old flasher unit while under the dash. Pull and clean the headlight terminals, pull the turn sig and brake light bulbs and clean the sockets up. Make sure battery is DISCONECTED!
