Hey. I got a 93 cobra with a bad drain on the battery(down to 3 volts in a matter of 5 days of sitting). I have pulled all the fuses and it still died, so it is nothing that runs through the fuse box. The person who owned it before me put 3 gauges, a monster tach, oil pres. and water temp. All are electric with lights. when the battery goes dead(below 7 volts) the tach goes up to the 8-10 thousand range. could that be my problem? COuld that be shorting out or something? Thanks for any advise you could give me.

 

What you have to do with electrical problems is more eliminate possibilites, so what I'd do first is disconnect all the stuff he added, especially the tach. Tape the connections so there aren't any full circuts and see if it still does it. If it doesn't there's gotta be something wrong with them and/or the wiring. At least then you'd know where to start. If that's not it get a workshop manual with wiring diagrams and see what might be draining power before the fuse box. The diagrams look intimidating but they're not too bad. Good luck

 

An easy way to check which circuit is causing the drain, is to turn off the key. Remove the ground cable from the battery terminal. Put a test light ($7.00 at your local auto parts store) and put it between the negative battery terminal and the cable. If it lights you know you have a drain. Then pull each fuse, one at a time. This eliminates one circuit at a time. When the light goes out, you now know that you have the circuit causing the drain (there is no longer a complete loop). Follow that wire and see if when he installed the gauges and tach, he tapped into that wire.
If the tach and gauges were installed before the key on, or directly from the hot lead, that might also cause a drain. Make sure he tapped into the wiring after the "key on" hot lead. An easy way to find that, is to to clip the test light to ground, and with the key on, probe each wire in the harness until it lights. Toggle the key a few times just to make sure.

Ron

 

thanks. I now know there is still a drain, even with the tach disconnect. The light should help me a bunch. Thanks for the advise, but that is now a weekend project.

 

Don't forget you also have relays and fuses under the hood to deal with besides the ones under the dash. Don't forget the hidden relay boxes too...like my wife's Bonneville has a relay box that I can't find at all!! Somewhere behind the passenger side kick panel...there's a weekend project for you!

 

Thanks everyone. The more information the better. I appreciate it.