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AC engages hard at high rpm

fisherangel7 on Wed June 24, 2009 1:44 PM User is offlineView users profile

Year: 200
Make: plymouth (dodge)
Model: VOyager (caravan)
Engine Size: 3.0
Refrigerant Type: 134a
Ambient Temp: 85
Pressure Low: normal
Pressure High: normal
Country of Origin: United States

I have plymouth voyager 3.0 that cools great but the compressor won't engage at idle on first engine start. It engine is revved slightly it starts (same for ac cooling fan).
Even worse, at high rpm it reengages hard (makes whole car shudder), but still cools great. This shuddering every 10 seconds is unaceptable. The freon has been checked and both high low pressures are good. What can the problems be?

( Thinking the compressor works great and disengages at high pressure, but wondering if there is some method or blockage by which the high pressure is not released well enough, thus it re-engages at already high pressure creating the hard start )?

Is it possible a blocked dryer could allow it to cool great but not release enough pressure fast enough?
Is it possible the expansion valve, same?
THANKS>. replys can go to [email protected] also on AIM if convenient. Thanks !

It was blowing hot.. so I put in 2 cans of freon with stop leak., with same problems as above remaining, a friend later put in more freon (probably overfilling it ). Later a technician drained it down to normal pressures high and low. Same problems as above remain.

Christ = King of Peace (not war)!

TRB on Wed June 24, 2009 2:02 PM User is offlineView users profile

Check you clutch gap for starters, 20 thousandths is about right.


When considering your next auto A/C purchase, please consider the site that supports you:

fisherangel7 on Wed June 24, 2009 2:12 PM User is offlineView users profile

ADDITIONAL: I should says it cycles at high rpm (ie 45 -70 mph) every 4 seconds approximately give or take.. is that too fast? what would cause the clutch and fan to not come on right away at idle (throttle position or speed sensors? or is it computer? or other? thanks)

Christ = King of Peace (not war)!

fisherangel7 on Wed June 24, 2009 9:37 PM User is offlineView users profile

I finally go to talk to a dealer ac man: he said it "might" be the high pressure switch (transducer) not staying off long enough for the pressure to release enough, he said 4 seconds was way too fast a cycle time. He said for a 3 wire pressure switch (which this car has) I could jump it by using a 1.5 volt AA battery, first determine which wire was ground and which was hot etc. (? not exactly sure on this how to do it, any ideas?)
He also said the compressor could be bad. But hey it cools great so far.. so maybe I should just live with it.
He also agreed that the Throttle position might be bad for the other problem of not engaging unless revved slightly. Any ideas are welcome without judgement.

Christ = King of Peace (not war)!

jglanham on Thu June 25, 2009 3:18 PM User is offline

It sounds similar to a problem I had on a '95 Chrysler. Try tapping on the pressure sensor (it is not a switch & never, ever try to jumper it.) See if the clutch pulls in and out when tapping on the sensor. Also, wiggle the wires coming out of the sensor connector. The sensor could have a broken connection internally (that was the problem with mine) or the connector could be corroded or faulty. Also, as it has been said many times on this forum, adding sealer to stop leaks on an a/c system is the kiss of death. Good Luck!


mk378 on Thu June 25, 2009 3:34 PM User is offline

On most cars when the engine can't maintain proper idle speed, the computer will (temporarily) kill the A/C to try and prevent stalling. For example, the idle air valve may be blocked or defective and not letting enough air into the engine to keep the rpm up.

Edited: Thu June 25, 2009 at 3:35 PM by mk378

fisherangel7 on Tue June 30, 2009 11:33 AM User is offlineView users profile

Well actually... it started so hard I thought it couldn't be loose belt or loose clutch,,... i let it sit for 2 days (driving electric car instead) by chance,, and "Bawallah" it fixed itself?? Now reflections tell me perhaps it was kinda locked (similar to ol fashion vapor lock in which the gas pump when heated in hot summers would vaporize the gas and try to pump vapor which prevented gas from coming in in any more than dribbles.. pow pop bang ). .. but this is kinda of a high pressure liquid lock in which the pump never gets to release the pressure but actually cools great too, the problem was that it would start hard and made the whole car shudder enough to jiggle the things laying on the cup tray (meaning perhaps that it never released the pressure when cycling on./off every 5-10 seconds at high rpm... thinking that this was case because if pressure released what else could cause that shudder? ) .

Anyway its fixed on the that problem for 4 days running now. And so far have escaped expensive dealer checkout/ diagnostics.

the other problem 2. is that it won't engage at idle on first start up, so I'm thinking its separate problem that is possibly a bad sensor such as Throttle position or speed sensor,.. it will engage if slight revving is applied to throttle (just a little bit does it..) after that it works fine. I can live with that.. thanks for your help and advice. As MK378 said.. maybe an idle problem.. if you want to see a patent that gets 2x the power out of batteries.

Christ = King of Peace (not war)!

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