Air Conditioning Question

[Texun]

My AC blows good cold air under acceleration but once I am at speed it kicks out and stops cooling. If I hit the gas to pass a car the AC blows cold again.

I thought it was low on refrigerant and bought one of those 134A recharge kits that comes with a gauge on the can at Autozone. I followed the instructions and checked the refrigerant according to the temp scale on the gauge with the engine on, compressor running and it shows full. Since it showed full I disconnected the can and left it as-is.

Assuming the gauge is correct what else should I be looking for?

 

[Zenmervolt]

The vents are controlled by vacuum solenoids. Somewhere in the vent control system you have a leak, or more likely a busted check-valve, that is only ducting air through the A/C evaporator when you're accelerating and do not have a lot of engine vacuum. Those are buried under the dash and usually not a lot of fun to fix.

ZV

 

[PandaBear]

Maybe the compressor clutch or belt is slipping?

 

[JeffreyLebowski]

Originally posted by: Zenmervolt
The vents are controlled by vacuum solenoids. Somewhere in the vent control system you have a leak, or more likely a busted check-valve, that is only ducting air through the A/C evaporator when you're accelerating and do not have a lot of engine vacuum. Those are buried under the dash and usually not a lot of fun to fix.

ZV

Zen is correct. I spent a week tracking this down in my old 3rd gen.

 

[Texun]

Originally posted by: JeffreyLebowski

Originally posted by: Zenmervolt
The vents are controlled by vacuum solenoids. Somewhere in the vent control system you have a leak, or more likely a busted check-valve, that is only ducting air through the A/C evaporator when you're accelerating and do not have a lot of engine vacuum. Those are buried under the dash and usually not a lot of fun to fix.

ZV

Zen is correct. I spent a week tracking this down in my old 3rd gen.

Well that was not what I was hoping to hear but it makes sense. A drop in vacuum would screw up the controls.

One thing I haven't confirmed yet is if the compressor kicks out once I am at speed. If it is then it wouldn't be a vacuum problem, would it?

 

[Zenmervolt]

Originally posted by: Texun

Originally posted by: JeffreyLebowski

Originally posted by: Zenmervolt
The vents are controlled by vacuum solenoids. Somewhere in the vent control system you have a leak, or more likely a busted check-valve, that is only ducting air through the A/C evaporator when you're accelerating and do not have a lot of engine vacuum. Those are buried under the dash and usually not a lot of fun to fix.

ZV

Zen is correct. I spent a week tracking this down in my old 3rd gen.

Well that was not what I was hoping to hear but it makes sense. A drop in vacuum would screw up the controls.

One thing I haven't confirmed yet is if the compressor kicks out once I am at speed. If it is then it wouldn't be a vacuum problem, would it?

It would be extremely unlikely for the compressor to kick out at speed and only re-engage when throttle is applied. That's the opposite of how it's set up to work. The compressor actually kicks off briefly on most cars when heavy acceleration is demanded. If that system failed, the compressor would stay off all the time and not come on with acceleration and off with cruise. Additionally, even if the compressor cycled off, the vents would continue to blow cold for a while, then cool, then warm, the transition would be gradual, not immediate.

All of the signs point to an issue in the vacuum controls for the ductwork.

ZV