Hello there,

I bought this 2001 GMC Jimmy about a month ago, and I have been pouring money into it like crazy.

The problem:
Very hard start.
Runs rough.
Hesitation.
Alternator is getting extremely hot.
output is only 7 volts while running.
Unable to charge the battery.
Starts without the key.
Battery light stays on even after taking the key out.
Odometer light stays on even after taking the key out.
Security light on the dash keeps flashing after I take the key out.

Fixes I tried before I knew about the electrical issue:
Replaced the battery.
Full tune up.
Replaced distributor.

I found the electrical issue by accident when I replaced the battery. I noticed a non stock wire connecting the positive terminal of the battery to the terminal on the back of the alternator. I assume the fuseable link is bad and someone added this wire.

I took the alternator off and took it to 3 different auto parts stores and it tested good on all machines.

Something weird I noticed is that the 4 pin alternator connector is only using 1 pin instead of 4. The other 3 pins are empty and no wires coming out of them. Is it supposed to be that way?

I also believe that the sending unit is bad because it is showing low fuel all the time even when the tank is completely full.

Any idea on what might be the problem? I am about to give up

Thank you!!

 

Welcome. Are you reading 7 volts on a meter at the alternator or is the volt gauge in the dash reading 7 volts?

The non stock wire from the battery to the alternator could have been someone's attempt at the big 3 upgrade for the charging system. Check the engine block to ground and battery negative to ground wires.

A parasitic drain/draw test should determine which circuits are the problem and give you an educated direction to continue your search. Lots of you tube videos on that test.

If it starts without a key the ignition switch is an obvious problem. I'd replace it and see what problems remain.

We're here for you Sam. Keep us posted.

 

Thank you!

I'm reading 7 volts on the meter. It is the same if I connect it to the alternator or the battery. I will check the ground and do the test tomorrow. Will let you know what happened.

 

Security light flashing, odometer light, battery light, and the ignition turning without the key, are more than likely all related to a combination of the ignition lock cylinder and or ignition lock switch, and or Passlock sensor. If the vehicle was stolen at one point, and the lock cylinder was forced, that might explain those issues.


Only two wires go to the alternator: Battery positive to the rear post, and one 16ga wire in the plug on the side. As mentioned, check the body ground and the battery negative cable connection to the engine block. The PCM controls the alternator on this vehicle, so voltage on the small red wire will vary depending on what the PCM commands. This makes it difficult for the auto parts store testers to accurately test the alternator, and the results can not be trusted. Best to test it on the vehicle.

 

I was typing and Captain beat me to it. Listen to him. I'd say he has forgotten more than I know but that's accusing him of forgetting something.

 

"Something weird I noticed is that the 4 pin alternator connector is only using 1 pin instead of 4. The other 3 pins are empty and no wires coming out of them. Is it supposed to be that way?"

I always thought that was weird, but it is correct.

 

Post #4 answers that question.

 

It does, but I always thought that it was weird that they put a 4 pin connector on for 1 wire. Not a big deal or an issue of any sort.

 

If you look closely in the connector, there will either be 2 or 3 vacant cavities that do not go all the way through. If yours has a cavity that goes all the way through, it will have a rubber plug in it.