When I engage the A/C or flip back to heat, the vents all make the right noises to let me know they are flapping into the correct positions, but that familiar sound from my other Cougars of the engine revs dropping slightly and the compressor engaging doesn’t happen. Any troubleshooting ideas? On visual inspection under the hood, the compressor clutch doesn’t appear to be doing anything. I’m thinking it might be a bad a Micro / Mode switch or a bad compressor clutch, but I would prefer to solve with a multi-meter/circuit tester than start swapping parts and praying.
Thanks in advance for any insight you can provide!
About all you can do without pulling the A/C-Heat Selector is to check the fuse and for voltage at the clutch when it should pull-in. No voltage means one of the two switches in the selector isn’t working.
I feel silly…again. I had looked at the fuse which is a thick band 30A and visually inspects as not blown, so I assumed it was OK. After doing a continuity check on the fuse box tabs, it didn’t connect, and when I pulled the fuse out of the box I found it was corroded and would continuity test intermittently, depending on where I touched the probes. (I hear Royce and a few others sighing right now…told ya…so…)
It’s late, so I’ll clean the fuse and probably need to pull the box off the firewall and do a full corrosion inspection. I’ll update when I have time to get it done.
Yes, the fuse box terminals being corroded is a pretty common issue in any old Cougar. You can clean off the corrosion with a Dremel tool or equivalent. Then slime the fuse with Vaseline before re - installing it.
Ideally you would use conductive grease on electrical terminals and battery posts since dielectric grease is an insulator. They sell conductive grease at Home Depot for use on power lines into your breaker box. But dielectric grease is less messy, and I guess the points of electrical contact on terminals probably scrape through the grease coating anyway.