Wierd?

[AJ02]

'02 GTS. It finally got warm enough for me to turn on the A/C yesterday. I found that when I accelerate fairly hard, the A/C fan stops?? Any idea on what would cause this? The car goes from comfortable to hot in about 2 seconds. Other than that, everything seems fine.

 

[V10SpeedLuvr]

Its normal. It cuts the AC off to increase performance when you really get on the throttle

 

[DrumrBoy]

Stop accelerating so much. Don't you know that these cars aren't meant for such abuse

 

[Allan]

PCM strategy for optimum driveability, WOT A/C cut out. All cars do this. Typically TPS at greater than 80%, PCM disables compressor clutch to reduce parasitic load on the engine.------Assumes your trying to pass a truck or something, so to allow all engine power available to drive the wheels instead of the compressor also. (to help you get around that truck safely) I don't think that Vipers really need this to happen, probably something mandated by 'big brother' I guess. (little 4-cyl cars need this) ---in a big way, the a/c uses half the power in a honda Again, PCM strategy, so those of us with aftermarket tune may not have this issue? It would depend on if that is one of the parameters selected to be changed by the programming guy or not. If it can even be over-ridden. I have SCT (roe), never paid attention to WOT a/c function, as I'm kinda busy whem my foot's in the kitchen! --hope that explains it well enough. -Allan

 

[bluesrt]

figure its like a 5 hp baby supercharger under the hood, and its all free,just floor the car,and waalaa- you got 5 more hp.... its actually to keep from explodeing the front head off the a/c compressor

 

[AJ02]

Stop accelerating so much. Don't you know that these cars aren't meant for such abuse

Sorry!! I guess it makes sense for the little rice burners. The only 4 ****** I ever had was a 1966 Austin Healy with no A/C.

 

[eucharistos]

a/c in mar/apr

 

[AJ02]

Wasn't necessary, just thought I'd try it and see if it worked at all. Only had the car since early Dec. and it's hard to see if A/C really works when it's 40 degrees out.

 

[Matt M PA]

Are you sure the fan shuts off? In some cars, when accelerating in a higher gear...vacuum drops and directs the A/C out the defrost vents.

 

[DarcShadow]

Tha'ts most likely what happened if you actually noticed a change in temp. The vacuum drop caused the door to open (or is it close) and allow the heat to blow through the vents rathen the cool air. There's a thread on here some place about how to fix the problem by replacing vacuum valve. There's actually several threads on this topic.

 

[WDW MKR]

Typically, cars cut the A/C compressor at WOT to avoid overspinning the compressor and causing damage. Modern PCM stategies include a delay for the re-engagement to ensure the crank pulley speed has slowed.

 

[DarcShadow]

Yeah, but during the short period that the compressor is off, you're not going to notice a drop in temp of the air coming out of the vents. The coils that are cooling the air, are still going to be pretty cool and the air will continue to be cooled. If the air is suddenly getting warm then the air coming out of the vents is not being passed over the cooling coils.

 

[AJ02]

The statements about the check valve make perfect sense. I tried the link here in this thread and it goes nowhere. I'd at least like to know if I can access it through the radio hole, or if I have to completely disassemble the dash to get to it. Can't find any working links on the forum for this info.

 

[Matt M PA]

If memory serves...there's a check valve that can be installed at the passenger side manifold hose to help stop the air direction changing to the defrost. (If that's the problem you're having)

 

[AJ02]

Well, I found the check valve and it holds 25" of vacuum. Any ideas??

 

[AZTVR]

Well, I found the check valve and it holds 25" of vacuum. Any ideas??

OK, stupid question, maybe; but, is the valve installed in the correct orientation? (i.e., it does not hold vacuum if tested from the manifold hose, and does hold vacuum if tested from the heater door side?)

edit: CORRECTION: It should hold vacuum from the manifold side until you disconnect the heater door side and then not hold vacuum. Just doing a single check for "holding vacuum" from the manifold side hose doesn't prove that the valve is OK.

 

[AJ02]

OK, stupid question, maybe; but, is the valve installed in the correct orientation? (i.e., it does not hold vacuum if tested from the manifold hose, and does hold vacuum if tested from the heater door side?)

edit: CORRECTION: It should hold vacuum from the manifold side until you disconnect the heater door side and then not hold vacuum. Just doing a single check for "holding vacuum" from the manifold side hose doesn't prove that the valve is OK.

Unless I'm thinking backwards, shouldn't it hold vacuum from the heater door side? The engine pulls vacuum on the heater door and when you accelerate, that vacuum drops. Seems to me the check valve should close and hold the vacuum between it and the heater door to keep it in the same position untill the engine vacuum comes back up.

 

[AZTVR]

Unless I'm thinking backwards, shouldn't it hold vacuum from the heater door side? The engine pulls vacuum on the heater door and when you accelerate, that vacuum drops. Seems to me the check valve should close and hold the vacuum between it and the heater door to keep it in the same position untill the engine vacuum comes back up.

I probably confused people. Whet I am meaning to say matches what you are saying. If the valve is connected to nothing other than a vacuum tester, then it will hold a vacuum pulled on it on the heater door side and not on the other side. If you leave it connected to the heater door actuator and test vacuum from the manifold side connection, it should also hold the vacuum unless the heater door actuator or line is leaking. At least that's my understanding but its been a few years since I troubleshot my system and replaced the valve.