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Manual HVAC. It seems when ever my daughter hits bumps the HVAC goes crazy. Fans will stop working or start working, blend door stops and starts working and fan position will be stuck and unstuck. Seems to be a loose connection or ground. The inside lighting seems to be affected as well. Where should I start? I am going to head out in a few and check fuse boxes, etc.

You could start by checking grounds 200 and 201. These are on the side of the footwells on each side, just below the lower dash panels.

I cleaned all the grounds in the trunk, under the back seat and under the hood. All of them looked good but cleaned them anyway. Found fuse 33 under back seat blown. Replaced and HVAC works. I will see later if I get heat as the acculator seems to be stuck before this happened. May be connected to fuse issue or bad acculator. I recall that fuse 33 blew a few years ago and I had the same exact symtoms. Fuse may have not totally blown causing a voltage problem. Consider this closed if I don't re-post here. I will clean grounds 200 and 201 if I have problems. Thanks!

Still no heat. Sometimes out of no where the heat will come on nice and strong. Once you turn off the car and restart no heat, just cold air. This has me stumped. intermittently bad acculator? I'll check those body grounds in the passenger compartment.

So now when this happens is the fan still working properly and it is just blowing cold air? If the fan is working fine, the shop manual goes through an 18 step process. The first is to turn off the AC and make sure the AC compressor clutch is not stuck in the engaged position which means the Ac is operating. Then check for low coolant. Then check the air temp actuator and turn the control from hot to cold and make sure the shaft rotates. Then check for broken linkage or stuck air temp control door, then the rest of the tests involve checking all the wiring.

bobgto65 wrote:So now when this happens is the fan still working properly and it is just blowing cold air? If the fan is working fine, the shop manual goes through an 18 step process. The first is to turn off the AC and make sure the AC compressor clutch is not stuck in the engaged position which means the Ac is operating. Then check for low coolant. Then check the air temp actuator and turn the control from hot to cold and make sure the shaft rotates. Then check for broken linkage or stuck air temp control door, then the rest of the tests involve checking all the wiring.

Thanks, good info here. I'll try once we thaw out.

Just an update- Bad actuator!