HVAC just stopped
 

Hey guys, got a little issue and I thought I'd see if anyone has run into a similar situation.

For the past week or so my HVAC (I say this because I'm referring to the entire system, not just a single component like the blower, the compressor clutch, etc.) has been cutting out and back in... just like quickly switching the main switch off and back on, maybe a half-second at a time. It's always come right back and then would work for the rest of the day or even days before it happened again so I dismissed it as a loose/failing connection and I'd address it when it got worse. Today it got worse. The system cut out several times within a few minutes and then stopped completely.

I haven't had time to get too deep into it, but here's what I've checked so far:

• All fuses are good
• All relays are functioning
• Removed, cleaned & reassembled the HVAC control switches in the dash. The contacts were dirty as expected, but I saw no indications of an obvious problem, and obviously the cleaning did not resolve the issue. One point of interest was the connector for the fan speed switch, which is looking a bit burned & melty... I'll add a photo later.
• Blower motor resistor: continuity across all three speeds with varying resistance readings on all three (didn't write them down, but I'm assuming for now that they're normal)

Prior to failure, the system worked perfectly, blowing cold air at all speeds and activating the auxiliary cooling fan normally.

I'm working at the office without my wiring diagrams in my repair manual, so I haven't researched what voltages I'm supposed to have at what locations yet but I wanted to post this in case anyone might have any insights for me by the time I get to the house.

Is anyone aware of any one component or wiring connection that's known to cause the entire system to shut down? This just screams pattern failure to me. The Jeep is a '96 SE 4.0 w/manual trans. Manual windows/locks, etc. I've had some issues in the past with some corrosion in my fuse block inside the cab, so that's where I think I'm going to look next when I get some time.

Thanks everyone!

I would check your wire going to the actual blower motor. This is accessed through the engine bay. There is one connector that plugs into the upper part of the blower. It may be loose. That is my only guess. Good luck.

Found it. Explains why the fuse still had continuity but the circuit was open.

Circuit may be slightly overloaded...
https://cimg9.ibsrv.net/gimg/www.che...a1cdbaa29e.jpg

I'm pretty sure the blower should work independent of anything else.
"One point of interest was the connector for the fan speed switch, which is looking a bit burned & melty" I might start there. Connections inside might have caused it to get hot, melting the connector.

Ha, funny! About 8 hrs and we post at almost the same time! Well, now you have your blower back. Motors like that sometimes go high amp when they fail. I've seen finger-nail files that work to burnish the inside of a blade connector. A folded bit of 200 emery over something really skinny might work to clean the female socket that that burnt out off...

Ha, weird! That's what I'm thinking... More twenty-year old components and whatnot. I guess it makes sense that it'd kill the entire system to protect it from freezing up with no air passing over the evaporator... I'm no AC man, I just know the general theory.

I'll probably err on the side of overkill and replace the blower motor, resistor and the connector on the speed switch.

Thanks for the replies, this has turned out to be a simple one so far... I gotta stop overthinking my jeep!