Hi there !

My wonderful blue truck is not right, and has had some really wierd happenings this week. 1979 F250 with a 302.

I do most all of my own work, the exhaust near the headers broke a bolt and able to remove 2 of the 4 bolts to replace them. I lacked the tools to fix this ( torch ). To a local shop.

When I picked the truck up, the solenoid would be the only thing chattering. Tried jumping it, just chatter. So we push-started it, started fine... runs good. Payed my bill and drove home. Found the starter went bad ( 2 years old ). No biggie, replaced it.

Jump started the truck and it runs great. BUT, now the lights are dim while it runs at idle, I only get 6 to 7 volts across the battery terminals, ok.... altenator.
I get a new 60amp alt and hook it up like the last one, good clean connections ( heavy guage wire to BATT terminal, and a small guage press on wire ( red/org ) to the white terminal on the alt. There is a black terminal also, but it wasn't used on the old alt. Not sure which one I should use, but looks like the setup in the repair manuel.

Jump started the truck and see I only get 9-10 volts.

I put a different battery in from my car.... 11-12 volts while the truck is running, didn't need to jumpstart it. The headlight were bringter. I was able to start up 4-5 times before I had the solenoid chattering again.

While the engine is off, I get 12v to the batt side of the solenoid. While trying to start, I get 3v on the next terminal, 4-5v on the next and the starter side of the noid.
Solinoid was replaced last year.

Looked all around the engine compartment, the only thing odd is a small guage ground wire from the body on the left side does not connect to anything. I don't exactly rememeber if this connected to anything, its length allows it to go just past the altenator but no further than the fan. I can't imagine where it could go.

Now, can a bad battery cause all this?

While the engine is running, when you disconnect the neg battery terminal, is the motor supposed to stop?

Could the brand new altenator be bad?

Is the one ground a suspect?

Is there anything this mechanic I took it to could have done to cause these failures?

I am going to get a new battery to help rule that out... but this is a 2 year old battery that has been starting strong before the mechanic trip, and the truck frequently sits for weeks at a time, and still started on first fire.

Any help would be greatly appreciated!

 

This is not enough voltage. You should have least 14 volts or in that neighborhood wit the truck running. I would check the large wire coming from the alt. Somewhere along this wire there should be a fusible link. This link may be burned out. It's like a fuse.

 

Checked all the wiring, it all has good continuity. A test light between the NEG battery terminal and cable lights for a split second ( LED ) and is off. The DVM shows a crawling voltage increase over 1 minute from 1.77v to 10.3v ( thats where it seemed to slow or stop ), when I hook the test light in the circuit it discharges to about 1.77v and crawls up again when taken out.

Capacitor charging somewhere? Is that norm?



Well anyway.... tried to see if the altenator was putting out solo without being hooked up, I get about 3v on the BATT lead. The exciter lead is spitting out slightly above 1v.



Could this be a voltage regulator prob???

 

Where are you checking voltage? The testlight is between the neg battery and what cable? And you are checking it running or engine off?

 

Eh... sorry about that. That is frustration speaking. :-)

Engine is not running, and the test light is between the disconnected neg batt terminal and the neg batt cable.

I did go out and by a new $10 voltage regulator this eve ( thank heavens for late parts placed ), hooked it up and wham! 13.9v across the terminals, while running.

Seems like this cheap part caused me a big headache, and maybe even a good alternator ( and I did not even get the old one bench tested before spending the $37.

<sigh>
Thanks for getting my brain juices flowing. Lots of great info in the 'search' findings.