Volt Light, Please Help


New Member
Nov 2, 2003
Hay guys, have a question about my volt light. I have an 87 turbo T with 140,000 miles . Motor has about 6000. When I drive down the road every so often the volt light comes on, day or night. When the volt light is on I cant give it more than quarter throttle with out the motor back firing . The light will stay on for about 10 to 15 min, city or highway driving. The car has a new battery and a brand new Napa Gold life time warranty 120 amp alternator. My guess is the cam sensor. Its like the cam sensor isn’t getting the right amount of power to deal with the timing. The car also back fires a little if your driving about 55 mph and you floor it and it down shifts to 2 nd gear. It does this with out the volt light on. Other than that it is the motor runs fine. If you start form a dead stop and floor it it runs great. (12.5 ¼ time) The car got almost all new sensors when redone but the cam sensor I did not replace. I think it is the original one. Please help!!!
I would get a volt meter and check to see what the alternator is putting out for current...It should be a least 13.o volts or more...My car when its running is charging about 14 volts with a good battery...If you're not getting the right amount of current your fuel pump won't be putting out what its supposed to and the car can miss...Happened to me once I was using underdrive pulleys and the car was running good 12.50's and I dropped to 13.8 then I found the problem.....The pulleys I were using weren't charging the battery enough at idle...HTH
Check to see if you have a 640K6 belt installed. These are too long and slip and could cause your problem. The correct belt size is 635K6.

Any auto store can check the output from your alternator. It is possible that even a reman alternator can have problems.

If the belt is good and the alternator is good, the problem may be in the brown wire that connects to the back of the alternator. This wire goes from the alternator through the firewall at the connecter below the brake master cylinder and then to the instrument cluster plug. When the instrument cluster is installed, the resistor in the instrument cluster provides excitation for the alternator.

You can run a jumper wire from the wire that goes to the alternator, located just behind the instrument cluster plug to the back of the alternator to bypass the circuit and check for any bad wiring.

Another alternative is to get one of the "field fix" harnesses from one of the vendors on the board.