[Brawler]

Volt meter on my 77' k5 use to read 14 volts, now it only reads like 12. Replaced the plug in wire on the alt but cant figure out why it started doing this. Is my alt going out or is it a wiring problem

 

[Buddha's Ghost]

If you get 12 volts at the battery when the engine is running go get a new alternator.

 

[Busto]

Get a VOM and check the output voltage at the alternator. If it is still 12 volts then your alt (volt regulator) is shot. Otherwise, it is the gauge. My bet is is that your voltmeter is good (trust your instruments!). Diodes do slowly degrade before they fail.

 

[Brawler]

Thanks

 

[TNToy]

You can try the old "disconnect the battery while the engine is running" test to see if the alternator is doing it's job, but it's hardly scientific.

Testing the battery with a voltmeter will usually show you about 11-12 volts with the truck off, and 14+ with the truck running and the alternator pumping away.

 

[jasonmt]

Rebuild kits for G.M. alternators are usually under $20 at your local auto parts store.

 

[slopoke]

yea depending on the area sometimes you can find an alternator rebuilder. well they also rebuild starters and all sorts of electric motors. anyways you can sometimes get high output units for the same price as a 80amp or whatever from NAPA. just an idea