So, I have a problem when my car is on the battery reads barely 12.0 v. For some reason it seems that the alternator is not charging the battery. My new alternator was tested and it tested good, also the battery is a brand new battery. However, when the car is off the red wire going into the alternator which is suppose to be an ignition as some people have told me continues to stay on even when the car is off. The car is a 1991 gta trans am, by the way sorry for not giving that information up front. could it be a loose ground somewhere, or would this problem be easily correted by cutting the red wire and running my own to an ignition source. Also, my tach is not working now don't know what happened to it does anyone know how I can test that. These are the last two problems holding the car back from being completed and now that the snow has come you guys know I just have to finish it because it would be bitter sweet to have a 450hp car just sitting in the garage begging to be driven, it's like having a 16000 toy that you can't play with. Well anyway please help me with any information that you can I'd appreciate the input and as always, without you guys this car wouldn't have been finished it's the home stretch and I plan on finishing this project to show the car in the spring and let people eat their words that said this car was a big waste of time.

 

I BELIEVE THE REASON FOR THE RED WIRE STILL SHOWING VOLTAGE, EVEN WHEN THE CAR IS OFF, IS BECAUSE YOU ARE GETTING A BACKFEED OF VOLTAGE FROM THE BATTERY. THAT IS A NORMAL SITUATION. DO YOU HAVE A LOT OF ELECTRICAL DRAW ON THE SYSTEM? TRY TURNING EVERYTHING OFF WHEN THE CAR IS RUNNING AND CHECK THE VOLTAGE AT THE BATTERY. THEN TURN EVERYTHING BACK ON AND READ IT AGAIN.

 

You never mentioned anything about having a hard time starting, or a battery drain. It might just be that the gauge is off. Try checking with a VOM while it's running to find out what the voltage actually is. The big red wire on the back is supposed to have power at all times, it is direct to the battery. The smaller one if I remember right(no manuals with me right now) is from the ignition, and should be off. It could be the ignition cylinder if that's it. If there is a drain, you can try disconnecting the harness to the steering column and see if it still drains.

 

yes it is the smaller red wire from the two. it runs along with a black wire next to it and feeds into a harness. As for the guage, its in the cluster and it did work before now it doesn't work i have an msd digital 7 hooked up to the car could this be causing the tach problem. I have had problems turning the car on because it just doesn't have power to crank after a couple of times so i do think that the small red wire is draining. i think it is suppose to be an ignition also. Should I just run an ignition wire to it to save me the trouble of trouble shooting? As for the tach maybe I should just install one , but what wires would i have to find and hook it up to?