AC cuts out under the smallest load

[DARKPT]

My '01 5-spd Touring Edition with 70k miles has started cutting out the AC under all but the very lightest throttle loads. The fan is unaffected, there's just no cold air. I can feel the AC kicking on and then right back off repeatedly as I drive. If I pull to a stop and let it idle, the AC comes back and blows nice cold air. I've checked the refrigerant level and it's good. I pulled the AC relay and swapped it with the horn relay just to see if that was squirelly (it wasn't).

I'm thinking its the throttle position sensor, which according to the books will return a certain voltage at high throttle input to allow the PCM to cut off the AC for more acceleration, or one of the sensors (high or low) on the compressor that have gone sour.

Does anyone have any experience with this?

[Ali N I]

I have seen the PCM cause this kind of problem. If the car is running fine otherwise, I dont see the TPS causing this. The PCM takes the signal from the TPS to figure out if it should cut the AC or not.
I had a guy locally with a PCM that caused his AC to not work at all.

[PT_Sean]

There is a switch, if memory serves, the WOT switch- wide open throttle- It's intent is to de-clutch the A/C so that as much engine torque is used to drive the wheels and not the accessories, ergo, A/C compressor, when needed, hence, a matted accelorator.

Again, going on memory, some 01's were invited back to the dealers to have their P/BCMs reflashed to change the a/c cutoff point. Sorry- its been almost 7 years, try a search on REFLASH or similar, her.

S

[DARKPT]

UPDATE:

The problem persisted as intermittently until last week when it finally gave up for good. The dealer had it today and replaced the cooling fan. It turns out it was not coming on, causing the PCM to shut off the AC. Problem fixed, and I damn-near froze my toes driving it home with the AC on MAX.

[FranksredPT]

I can set my cruise control, turn on the a/c and if going up a somewhat steep hill, the a/c will cut off if the car drops down a gear. As soon as the car levels out, the a/c comes back on. If the cruise is not on and I'm going up the very same hill, the car will drop down a gear but the air stays on. Only happens when the cruise is on.

[gumpster]

The cruise may give it more gas when going up that hill than you do. I've noticed that the cruise does not care how far down it mashes the pedal to maintain the set speed.

Maybe the cruise has a "heavier foot" than you do going up hills?

[QuicksilverDon]

Originally Posted by DARKPT

UPDATE:

The problem persisted as intermittently until last week when it finally gave up for good. The dealer had it today and replaced the cooling fan. It turns out it was not coming on, causing the PCM to shut off the AC. Problem fixed, and I damn-near froze my toes driving it home with the AC on MAX.

Wow, surprised you didn't have any overheating problems. The fan is 2-speed, suspect you only lost 1 speed.
Glad you got it fixed.

[PT_Sean]

Originally Posted by 1WEDWUDY

I can set my cruise control, turn on the a/c and if going up a somewhat steep hill, the a/c will cut off if the car drops down a gear. As soon as the car levels out, the a/c comes back on. If the cruise is not on and I'm going up the very same hill, the car will drop down a gear but the air stays on. Only happens when the cruise is on.

Originally Posted by gumpster

The cruise may give it more gas when going up that hill than you do. I've noticed that the cruise does not care how far down it mashes the pedal to maintain the set speed.

Maybe the cruise has a "heavier foot" than you do going up hills?

Sounds 100% normal. The cruise will pull the throttle more than you think to maintain its set speed. If mashed, WOT kicks in, A/C kicks out.

Good find on the fan though.

S

[DARKPT]

Well, &%$#!

I was 3 miles into a 70 mile drive home from the airport this afternoon, and the AC went right back to where it was when the problem first started. If I'm anywhere above just a partial throttle, the AC cuts out. If I kick in the clutch for a few seconds (fun to do at 70MPH!) the AC comes back on and will stay on until I have to give it a little gas (not WOT with cruise, just a little).

The car was not overheating before the fan replacement on Tuesday. Stay tuned as I dig the checkbook back out and find out what's really wrong with it next week.