For some odd reason, I am only running 11 volts now. I was running 13.5 before I hooked the tach up. Does a tach use that much juice? Could it be something else? Or am I just being paranoid.

 

Sounds like the alternator is no longer charging. Its probably unrelated and came up on its own but who knows..

 

alternator is new, but I am gonna check it anyway. i am thinking the battery is taking a crap.

 

Ok, I fully charged the battery today, then started her up. She ran at 12v, which I still thought is kinda low. The only extra electrical load I have is the tach itself, and the voltage gauge.

I found it odd that when I revved her, the volts went down some, then went back up to twelve.

I am think it is the battery.

 

hmmm... Even with a nearly dead battery there should be at least 13.5 or more volts when the car is running. The alternator will normally supply all of the cars power needs when its turning.

Use a volt meter and verify that the voltage at the battery remains at 12 volts with the motor running. Disconnect the connector for the alternator and turn the key to the ON position but dont start the motor. At the two red wires there should be +12 volts and also +12 volts at the tan/white wire. If all of those have voltage then, for whatever reason, the alternator itself isnt charging.

 

well, had them tsted, alt was bad. Replaced it, and I am still running at 12 volts. There has t be something that I am missing, a wire touching or something. Any ideas?

 

First, did you verify with a DVM that it really is at 12 volts with the car running? I take it you (or those who worked on the car) probably did. Second, how did you wire up the tach? There is a switched lead that provides power to the fan as well as the circuitry in the alternator that energizes it. If that was cut or inturrupted then the alternator wont work. Check the fuse that will be marked, I think, 'FP FAN FUSE' in the fusebox and make sure its not burnt. If that checks out then with the key in the ON position, check to be sure that both red wires + the tan/white one have +12 volts. If they do, then there isnt much reason the alternator shouldnt work.

 

My fan is hooked up on its own switch, doesnt go through any of the stock wiring. The alt has worked fin up until now. I got a new one and it still just reads at 12, and will start losing volts if I put alot of power to it.

The tach is hooked to a open fuse hole in the box, with an inline 5 amp fuse in it. The ground is grounded good, and the lights are working fine, and the tach gets its signal from the tach ref wire

 

If you havnt bought a good digital volt meter now would be the time. Im no expert but IMO you should check those wires I mentioned above to be sure that they have power when the key is in the on position. Also make sure you dont drive too far with a battery that isnt charging. Driving back home with no headlights in the middle of the night because the battery is down to a few volts is no fun...

EDIT: you should also check the main lead on the back of the alternator as well. That should have +12 at all times as it leads to the battery