AC electrical gremlin - calling all electrical gurus

[E9Wayne]

Hey folks, Don is working on this too in between some other jobs he has now, but looking to the group for relevant experience that might help me here. First, the good news, Don fixed my car in August and she's finally cured of the 12 month intermittent coil problem after lots of repairs and replacements of other parts...

Now to the AC, after a new evaporator and expansion valve that was installed by Chris this Spring, I got the R134 refill at my local repair shop a few weeks ago and they found out that while the compressor would turn on, the switch do so would not fire the compressor. After Chris' last visit and installation of the evap/expansion valve and a new AC temperature switch and some wiring upgrades, it turns on the new AC temp switch is receiving power but not sending it to the compressor.

Don has sent me a new AC temp switch that I have yet to install but a new problem has surfaced...

After trying to diagnose the problem with the aftermarket AC temp switch, I subsituted my old OEM switch and found some electrical shorting at the spade connnectors when I did that; thereafter, the AC switch would not fire up the AC evaporator fan in the console whereas it was working prior to the shorting episode.

I've looked all the way to the fuse box and the green/blue wire coming out of the fuse block and the connections are good and I get 12V at the upper and lower portions of the #8 fuse. So the problem appears to be between the fuse box and the AC fan switch which is not showing any 12V power. The wiring diagram shows a straight path between the fuse box and the AC fan switch. Per Don, I removed the electrical connector to that AC fan switch and tested for voltage at each of the three connectors inside, but no power. So the switch is probably okay?

A very weird problem that I'll get more ideas from Don next week, but hoping someone here might have had a similar experience that I've not looked at yet...

Thanks in advance, all!

 

[Dlc]

Could you post a picture of your wiring and switches, this would help me a great deal to visualize you setup.

 

[Dick Steinkamp]

If it is stock, the AC electrical system looks like this...

 

[Ohmess]

Wayne - random thoughts. You mention shorting, and that your blower fan no longer works. Is fuse 8 intact?

Assuming it is, you indicate you have power on both ends of fuse number 8, but no power on any of the terminals at the fan switch. This indicates to me that you may have a problem in the blue/green wire that runs from the fuse block to the switch. This seems odd, since there are no connectors, but next step here is to check the blue/green wire for continuity.

The fan switch provides power to the blower fan, activates the relay that shuts off the heater fan, and provides power to the temp switch for both the compressor and condensor fan. If your blower fan doesn't run, and you don't have power at the fan switch, your compresson and condensor fan won't run. In other words, you need to address the upstream problem of power to the fan switch before moving downstream. Impossible to say right now if the switch is ok. Get power to it first, then address the blower fan, then move on to the temp switch and the rest of the circuit.

 

[Arde]

.. This indicates to me that you may have a problem in the blue/green wire that runs from the fuse block to the switch. This seems odd, since there are no connectors, but next step here is to check the blue/green wire for continuity.

Exactly, there is mention of electrical shorting happening, if said shorting was determined the hard way (not by measuring continuity but by rather energizing the circuit) the wire may have overheated and be compromised (either open or short to another one).

I agree on checking continuity of that circuit.

Usually voltmeters don't distinguish between an open circuit (zero voltage with high impedance) vs. a short to ground (zero voltage with very low impedance) so it is best to measure continuity.

 

[sfdon]

Your new switch shipped yesterday..

 

[E9Wayne]

Thanks, all, and this is quickly evolving into a problem about my skill level as chasing this down would seem to need removal of lots of stuff!...I agree that there seems to be an issue somewhere between the blue green wire exiting the fuse block and the AC fan switch, unless I'm not measuring accurately at the fan switch input plug with power, etc. Don, I'll be in CA this weekend onward so maybe we can catch up then on this or when you next come out here. I'm so close to having a complete AC system -- everything is new or upgraded and the remaining fixes are these new switches and a wiring issue somewhere that I must have caused.

 

[Arde]

Where is the car located? It should be easy to measure continuity to the AC switch, and if needed string a new wire to it.
The other option is to remove the AC altogether and save the weight and hassle. For 70s cars less is more.

 

[E9Wayne]

Happy ending, guys. Don just wrapped troubleshooting and repair. The AC fan switch green wire had a blown undersized 15 amp fuse put in by someone before me. And there was a loose ground wire too. After putting the console trim and shifter back, I enjoyed a nice drive down the street and I'd swear the AC has never blown more forcefully or cold (admitted 52 degrees here in Virginia today). So Bluebelle is back in action and ready for Sharkfest and Saratoga, at the least this year. And I'm hoping the Apple Series she got to star in 2022 will be coming out this year - it's called The Big Cigar. I'm hoping there are some good scenes with my car for all E9 fans to enjoy. What a saga of repairs and issues since the movie shoot, though! Thanks Don and Chris!

 

[bavbob]

How fortuitous!. I was cleaning out my basement and I came across a small harness from my E3, could not recall what it was but it is identical to Don's picture above. 10 years ago I needed a new AC switch and Koopman hunted one down for me that also came with all the wiring. I blame it on having too many cars rather than age.