My '94 Z28 has a voltage drop problem.

Normal driving, the voltage is between 14-14.6 volts as measured with my Fluke DMM. With all the accessories on and operating the power windows it will drop just below 14 volts.

BUT, if I mash the throttle and really get in it, the voltage will drop below 12 volts, lights will dim, and the car pulls like a scalded ape! I first noticed it at night (when the lights dimmed), and double checked with my meter (I don't trust the cluster for accuracy).

I am not sure what the problem could be. Is this normal? It doesn't seem like it should be. I don't hear any belt slip and the alternator seems to be charging fine.

Sorta lost about where to look for the problem and I don't want to start throwing parts at it. Any ideas?

 

The lower voltage and stuff is normal as long as it stays above 12volts. If it goes below that going full throttle check for belt slip first. Then get the alternator check out.

 

sure sounds like the belt is slipping at high rpms, have a look at the serpintine belt, is it lookin old or maybe some oil on it. it could be the tensioner is getting tired. the springs in em get weak after a time.

 

Yeah, first thought I had was a worn / old belt. But it looks like it was replaced just before I bought it in January. It is dark black and all the lettering is still bright yellow.

Is there a test for the tensioner? Can I put a torque wrench on it and see how much it takes to twist it? Any idea how much it should take?

Replacing the belt should be cheap and easy, but I don't have any idea how much a tensioner would cost. I would definitely go new, that's for sure. No sense in throwing in a used one that may or may not be better than what is in there now.

 

no cracks on the underside of the belt? the slippage on the alt will be on the ribbed side so look there for signs of any slip/glazing and or oil. if u havent yet try cleaning all your conections. the ground for the battery is behind the tensioner. clean the battery terminals and cable ends, do the wires to the junction box by the battery as well. could be a bad connection and when u hit high rpms the amps come up it loses the contact. should b able to have the alternator checked for free so u may want to do that before going with a new tensioner. is the belt squeeling? i found a new tensioner at rms.