Hold on. Throwing random parts at a problem is the most expensive and least effective way to diagnose a problem. There's absolutely no way the dimmer switch can cause a drain on the battery. If the head light switch is turned off, there's no current going to the dimmer switch. The switch could be shorted to ground, terminals shorted together, wires could be grounded, or anything like that and it wouldn't matter as long as the head light switch is off.
Same for the horn relay. That isn't doing anything, and if the horn works properly, it's unlikely there's anything wrong with the relay or circuitry.
Replacing an entire wiring harness is the same as tearing down your house and rebuilding it because one window is drafty. If a wire is broken or grounded or two wires are shorted together you will have other problems like a dead circuit, blowing fuses, or wrong things happening when you turn things on. It is extremely unlikely you will have a drain on the battery due to a wiring problem when there are no other symptoms.
Since your car is old enough to have no insane and unnecessary computers, tracking down a drain on the battery becomes real easy. The easiest way to start is by disconnecting the negative battery cable when you stop the engine, and reconnect it the next time you want to drive the car. If the battery is still dead, you have a bad battery and there's likely no need to look for any other cause. Also measure the battery voltage with the engine off, then again with it running. With it off, a fully charged battery will measure 12.6 volts. If you find around 12.2 volts it is okay but discharged. With the engine running the voltage must be between 13.75 and 14.75 volts. If it is low we will have to diagnose the charging system.
If the battery voltage is 12.6 when you stop the engine but much lower many hours later, disconnect the negative battery cable and connect a test light between the cable and battery post. You can use a digital amp meter too if you have one and know how to use it. If the test light glows, that proves there is current flowing and you do indeed have a drain. Start by looking for a glove box light or trunk light that isn't turning off, and an aftermarket radio that is wired improperly so it is not turning off. Also unplug the voltage regulator. Even though those parts are new, the regulator can be kept turned on when it should be off. That can result in up to a 3 amp draw which can easily kill a battery overnight.
If you haven't found the cause by this time and the test light is glowing, crawl inside the car and close the doors so the dome light goes off, then pull the fuses one at a time, and watch for which one makes the test light go off. That will be the circuit you need to follow.
Wednesday, July 17th, 2013 AT 9:21 PM