Thanks Cousin_Eddie, hope your swap is going well, too.
I didn't feel like getting too dirty today, so decided to go back to tackling the in cab wiring issue.
I disconnected the DRAC, since it really shouldn't be needed anymore with the ECM VSS signal going straight to the dash now. No change in the weird voltage issue.
Went ahead and pulled the gauge cluster, and was reminded of why I'd been stalling on doing this - requires pulling the heater controls, and a lot of connecters/clips in a very inconvenient position. Anyway, results from that:
RESULTS EDITED - I made some changes to the battery connection(improved the positive connection and added fusible links) and retested, plus I must have read something wrong before
With fuse in place:
Key off ~ 1.4 volts
Key on -.3 volts
With fuse removed:
Key off ~1.4 volts
Key on ~1.4 volts
That's weird. I plugged the gauge cluster back in, just to see if I had jostled something, but when I did, I went back to basically the same numbers I was getting before. Just in case the battery was drained, I switched to a fully charged one. Haven't pulled the cluster to replicate the numbers in this post, but the plugged in numbers were close enough I don't think it was the battery.
Here's my takeaways so far:
- The issue with the voltage drop/reversal is not in the gauge cluster itself, based on the differing results above with the fuse pulled or in.
- The cluster is somehow integral for power getting to at least the cigarette lighter and the radio wiring harness.
Going to keep messing around, maybe see if I can find some visibly damaged wiring, but I am pretty much flying blind. I might try to run some tests for draw across the fuses like I saw in a youtube video last week, but I'm not sure that will really reveal anything, since I already know roughly where the issue should be.
One thing I forgot to mention, I am not sure sure if this is relevant or not, but the orange wires that go to the OBD1 port do not seem to have power. Being a Chevy, I'm kind of assuming they should always be powered if the battery is connected and a fuse is not blown. Unless they are one of the random orange wires GM uses for something other than fused power.