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AC cuts out...

C

ConnContour

New CEG'er
Joined
Sep 23, 2001
Messages
23
My AC stops blowing out of the vents and to the floor when I give my Contour the gas. Just a mild pressure and the AC stops, let off the gas and it comes back in a few seconds. Car is 97, ATX, Duratec with 260,000 miles. I had just cleaned my throttle body and I'm pretty sure I didn't miss any vac connections. Funny thing is now, the last 2 times I've cleaned it, the crusie control didn't work. Now it works. I think this topic was discussed before. The AC still puts out around 42 degrees. Any insight?

ConnContour
 
The AC system unfortunatly is supposed to do that. It keeps the AC from bogging down the car so much.
 
The blower should still blow air, but it will be hot. The a/c clutch cuts off at wide open throttle to conserve power for possible emergency. Normal.
 
I get NO air flow from the vents. I'm not talking about wide open throttle either. Sometimes just going up a small hill will shut it down. I'm only pressing on the throttle maybe a quarter to a half an inch. When I let off the gas the air flow returns. My car never did this before. I'm wondering if outside temperature has something to do with it. This happens when it's over 100 degrees outside (yesterday 108).

ConnContour
 
Actually what happens is I still get air flow, but now it comes from the foot vents, nowhere else. Anyone?
 
Correct. The AC is set on MAX. It will be diverted to the floor vents when I give it just a little throttle. I let off the gas and it returns to the vents.
 
Interesting. I wonder if mine switches to the floor as well. I know the vents slow down but I always have shoes on and cant tell what the floor vents are doing.
 
Engine vacuum is used to pull open the various doors in the dash that direct airflow to vent, defrost or floor outlets. In most cars if the vacuum motor fails or you develop a vacuum leak, the default location is defrost or floor. An engine with that many miles is really tired and requires more throttle than a fresh engine to go up hills, move from a stop etc. More throttle means less vacuum to control the air exit location. There is probably nothing wrong with your HVAC controls, you just have symptoms of a very weak engine.
 
The engine is not weak none the least. I think it's probably a vaccuum leak somewhere that I can't find. I guess it's a good way to maximize my fuel economy with just a light pressure on the gas pedal.
 
rtbshome2 said:
An engine with that many miles is really tired and requires more throttle than a fresh engine to go up hills, move from a stop etc. More throttle means less vacuum to control the air exit location. There is probably nothing wrong with your HVAC controls, you just have symptoms of a very weak engine.
Click to expand...

No need to make assumptions like that. Happy older engine can put down just as much power as their younger counterparts.
 
Sounds like engine vacuum changes brought on by throttle changes. Not supposed to do that, I'd be checking the one way vacuum valve that is supposed to keep vacuum in reservoir when throttle opens. If passing air both ways now would make that problem. Had a Tempo do it once. I do NOT know where that valve is on a Contour, but system MUST have it somewhere. I'd start by running down the vacuum supply hose that supplies heater/ac system, sometimes it's inline with hose. Or could be built into the main vac reservoir tank somewhere under dash. Regardless, you can buy a one way or check valve at auto parts store to just put one inline if you can't get to the bad one. Either that, or a leak has developed in vacuum system or switch itself. A small one could still work everything at high vacuum but lose it all on any application of throttle. Don't confuse a power brake one way valve with a smaller one needed here, would work but fitting size too big. They both work exactly the same. Allows high vacuum to suck and fill tank one way, but shuts off when vacuum drops low to prevent loss in the reservoir. The loss to low vac is what switches the air doors.
 
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