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Discussion Starter #1 (Edited)
I sold my 97 tbrid to my nephew and he is having an issue with the A/C compressor coming on and off. Its causing the RPM to go up and down. It will do this with the AC or with heat on. I didnt think the AC Compressor should cycle when the HEAT is on. He says its rather annyoing because when sitting at a light and the RPMS kick up the car wants to creep forward on him. (I told him to just press on the the brake harder. lol)

This just started and has never happened before. Can anyone shead any light on this?

I did a small search here before posting. This was all i could find. In post #6 discribes the issue perfectly. http://forums.tccoa.com/showthread.php?t=141146

Didnt really see a resolution. Any help would be great. Thanks.
 

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The compressor normally cycles on EVERY setting except two - vent (panel) and floor (heat)
 

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The Parts Guy
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If he doesn't mind losing the dehumidifying benefit of running the AC compressor, then just unplug the compressor clutch.
 

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Discussion Starter #4
This is doing it on all settings.. Could it be the digital temp setting panel?

Well i would believe he still wants to have AC on hot days.

Im just trying fix it back to fully working order.
 

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Discussion Starter #6
Thanks. I will look into seeing if the level is low and need recharged.

Next is if i have to replace the switch. Then i have to recharge the system anyways right?
 

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Ehhh, the system will cycle normally under certain conditions, particularly when there isn't a lot of heat being removed from the low (cold) side or if the ambient temperature outside isn't very hot (50s through 70s typically). Running low on refrigerant would cause excessive cycling but the fact that it cycles in and of itself does not automatically mean it is low on refrigerant.

The A/C compressor will cycle whenever the HVAC control is turned on, regardless of the temperature/blend door setting, with exception to PANEL and FLOOR so long as the pressure in the system is high enough (ambient temps in the 50s or higher). If the clutch is engaging in PANEL or FLOOR as you have indicated, then your HVAC head might be faulty since it is what sends the signal to the PCM to command the A/C clutch to be engaged. But keep in mind, as you turn the selector dial to FLOOR you pass PANEL/FLOOR, which will engage the compressor for a few moments.
 

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Thanks. I will look into seeing if the level is low and need recharged.

Next is if i have to replace the switch. Then i have to recharge the system anyways right?
take your car to a reputable shop. DO NOT use those cheap ass walmart cans, they contain mostly compressed air. (i tried this before getting my car a/c recharged) You can get the a/c charge checked before replacing the switch... if the charge is full, your switch is more then likely bad.

Make sure the tech does a VACUUM (sucks out all the old oil/freon out of the line) and puts in 2.1 lbs of r-134a/oil into the low pressure side (port nearest to the shock tower) Should be no more than 2 hours and 200 bucks at the most.
 

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If it is cold outside your system may show all the symptoms of having low refrigerant charge. Refrigerant liquid/gas likes to migrate to the coldest area and condense there. So if its real cold out, the condenser coil will act like a reservoir (receiver) and liquid refrigerant will accumulate there. Be very weary of adding gas to any a/c system when the outside ambient temp is below 50*F. Also be aware that if you go to a random ac guy/car shop and tell them to sell you freon, they will! And you might not need it.

Edit. I see you are in St. Louis, its hot there. It sounds like the freon level is low. Hook up some gauges and look for 35psi/200-300psi. Pressure is not the way to charge something but that should get you close.
 
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