I'm putting my money on the headlight switch, I know you just tested it out of the car, but maybe there are other factors inside the car like a misdirected deforester vent in the dash that's causing extra heat? After having the lights on for 15-20 minutes, things get hot on the sweeper (resistance), and the relitively low current draw of the dash lights can't make the gap and bam, lights out. That's my theory at least.
The switches come apart pretty easily, you could try cleaning/adjusting the sweeper.
I'm putting my money on the headlight switch, I know you just tested it out of the car, but maybe there are other factors inside the car like a misdirected deforester vent in the dash that's causing extra heat? After having the lights on for 15-20 minutes, things get hot on the sweeper (resistance), and the relitively low current draw of the dash lights can't make the gap and bam, lights out. That's my theory at least.
The switches come apart pretty easily, you could try cleaning/adjusting the sweeper.
Yes, it can be a number of things, including the switch still, even though it tested fine on the bench. I put the switch back in the car and it worked about 5 minutes (dimmer had full control) and then died. I had a test light ready and the GY supply wire from fuse#3 was lit but the GY/BL wire (dimmer output to cluster) was dead. This could point to a bad switch or some high load dragging it down.
I pulled GY/BL wire out from the headlight switch connector and have it jumpered to the GY supply wire with an alligator clip (which basically bypasses the dimmer and make the cluster lights full brightness ( my normal setting). If this works, I am not doing anymore troubleshooting and will leave it as a permanent fix.
Since pulling the GY/BL wire, bypassing the headlight switch, the cluster lights worked for a short while then went dead and fuse #3 blew. I checked the resistance of the GY/BL wire to ground and it fluctuated from 4 ohms (way too low) to 10 ohms (still too low). Another resistance measurement later it went back to normal (around 16 ohms).
I think the problem is in wiring from the GY/BL wire to the cluster or something in the cluster itself. The GY/BL wire also powers the defroster switch lighting so I will check that also.
Got it fixed! I hope for good this time.
Pulled the cluster and found no shorts. Checked GY/BL wire resistance to ground with all loads disconnected and it was all over the place 4 ohms 8 ohms 12 ohms, even 1 ohm. Jumpering it to the GY wire would blow fuse #3 (more on that later). So I looked on other pages of the Bentley wiring diagram and noticed the GY/BL wire also powers the AC/heat control panel light, defrost switch light and cig. lighter light. These never worked before and I didn't know they were even lighted. Found a crimped GY/BL wire from the AC/heat panel light going to the cig lighter light. It had carbon on the insulation where the breach of the insulation was and likely where the intermittent partial short to ground was.
Now all the lighting works including a well lit AC/heat panel which I hav is e never seen before.
The cluster lighting is much brighter than before so the partial short was pulling down the voltage.
I am not declaring total success till I run this for a few nights without blowing fuse#3, speaking of which I made this from a burned out fuse.
Instead of keep blowing $$$ fuses while testing, I used alligator clips on a 2" long piece of solder as a fuse 1/4" apart. Everytime it blew, the 2" solder fuse is shorter by 1/4".
Good to see you stuck with it till success.
Good to see you stuck with it till success.
The cluster lights has been working fine since the repair with no cut outs so I am finally declaring success. It's been a head scratcher for a few months being an intermittent problem. I am glad I didn't buy another headlight switch or tear into the wiring bundles/ fuse box.
This problem still bugs me in that the GY/BL wire output from headlight switch dimmer daisy chains to the cluster lights, then to the defrost switch light, then the AC/heat panel light, and finally to the cig lighter light (which was never connected because I found the wire was cut from the cig lighter and just hanging). The lighting for the AC/heat panel and defrost switch never worked in the 3 years that I've owned the car and the cluster light always worked with no fuse#3 blowing or intermittent cluster light opearation until a few months ago and it was all due to this partial short to ground of the GY/BL wire which got progressively worse. If it was pulling down the voltage on the AC/heat light, why did it not pull down the instrument cluster light voltage along with it?
The headlight switch that I have is the one with electronics dimmer and not the one with a rheostat. Maybe that has something do do with it?
