I've been running 100W 9004 bulbs for three years now (the dealer's solution to poor Audi headlights) and decided to take the collective qlist wisdom to heart by installing a high beam relay system to off-load the headlight and dimmer switch. The plan was to run the low beams through the stock wiring (to get the DRL's and avoid the autocheck issue) and use the stock high beam and ground wires to trigger the relays. It seemed so simple!
The first hint of a potential problem was the observation that the stock sockets around the ground connection were burned and melted. Hmmm. Obviously a lot of current going to ground. Strange; would have thought the high beam connector would have overheated at 100 W.
I ran a 10 ga. wire up from the alternator, split it through two 30A in-line fuses, and ran two 12 ga. wires to 30A Bosch relays mounted above each headlight. Always one for providing a fallback position, I did not cut into the stock wiring but cannabalized a couple of old 9004 bulbs to make wiring sockets for the stock headlight connectors.
I picked up a couple of 9004 generic connectors from the local CTC and wired in a 12 ga wire for the high beam feed from the relay, connected the low beam feed to the stock low beam wiring, and a ran new 12 ga. ground. I connected the stock high beam wire and the stock ground to the relay coil. Everything looked great.
To make a long story short and avoid the painful reliving of the excrutiating details, there is enough voltage leakage into the high beam circuit to trigger the relays on low beam. The bulbs don't last long, but they sure are bright.
With the relay harness connected, there is 7.5 Volts in the stock high beam circuit with the dimmer switch in low beam position. Disconnecting one side of the relay harness and reconnecting the stock connector drops the voltage in the high beam circuit to 0.2 . The lights seem to work OK with the stock system connected.
Checked the new connectors and harness for leakage across the high/low beam pins - no problems. Horrors of horrors - could the dimmer switch be burnt?
Pulled the dimmer switch and checked for leakage between the high and low circuits - no problems. Checked the functioning of the dimmer and headlight switches - all OK. I was sitting in the car with the switches open in front of me feeling the rush of relief all was well when a willi-waw popped out of nowhere, picked up 4 pounds of sand from the driveway, dumped it in the car through the open door and ripped the roofing off the back shed. Sigh.I hope this isn't an omen.
Any ideas out there? The burnt ground connectors may indicate that this has been going on for some time with the stock wiring, although it has not been obvious in the visual functioning of the lights. Where is the power coming from if the dimmer switch is OK? Why is the power there when the relay harness is connected and not when one stock connector is hooked up? Does this have something to do with the headlight control unit - it doesn't seem to be wired into the high beam circuit according to the wiring diagram.
Most perplexing. Any insight will be appreciated.
'91 200q 250k km