Travis
Sorry for baling after Friday. Long busy weekend and my two year old's birthday kept my schedule slammed.
Merging some data from your PM's - I think the way you've sourced your ground for your meter is fine. Thanks for all the pictures, they helped get me on the same page. Your testing procedure is solid.
After reviewing your findings, I'm convinced that you've got a good ground signal coming from the blower selector switch and resistor on the white wire that goes to position 1G of the black HVAC connector G-01.
I'm 90% sure you've also determined that the problem is on the output of the AC switch / the Violet/Pink wire leaving position 1I of the HVAC black connector G-01. The only muddiness in the water is you said "No resistance with any combination of car on or off or AC on or AC off with blower position on #1."
No resistance to ground with your setup configuration on position 1I would mean your shorted to ground, which means your getting a ground on violet / pint, which is correct, but I have a feeling that's just a typo. Did you mean to say large / infinite resistance?
The reason I had you unplug G-08 was to try and determine if something in your micro relay / AC interceptor was wired and maybe shorting the whole ac switch to ground or something because of your 'no resistance' comment.
If you're getting a large resistance to ground out of the Violet/Pink wire leaving position 1I of the HVAC black connector G-01, I'm pretty sure you've diagnosed a bad AC switch / HVAC board. Which one, I couldn't say since the HVAC unit to regarded as a black box in the FD's wiring diagram. It literally only shows a simplified diagram of the AC switch and that's it, so that makes drilling down any further impossible, at least from my end. You could do a wire check to make sure your AC switch's wiring between the HVAC PCB and the actual switch (I think it's like a 4 - 6 wire jumper connector made of red or white wires) is fully plugged in without and crimped / fractured wiring (you could do a resistance check on each end of the connector for each wire if you want to be anal about it). If that checks out, I think you're down to swapping pieces of hardware to try and isolate the issue. You might reach out to someone like
Fritz Flynn who makes a side living off of parting out RX7s and see if he's got a working but ugly hvac panel you can test with. Or even better just the guts of an HVAC panel because I know he sold me just the plastic for one years ago (which is the high demand part), so maybe he disassembles them from time to time.
Failing extra parts to swap and isolate, I suppose you could break out your meter, tie one probe to chassis ground, then start probing the rest of the wiring on the AC switch / HVAC board to see if you can find an alternative source for the AC switch output. Such a source should mirror the AC switch's output logic, so with the blower on and the AC button depressed, you'd get a ground. Any other combination would float (I.E., not ground or 12V).
Best of luck
Lane
