Idles erratic when A/C is on

[Josh40601]

Alright guys and gals, no clue why the truck is doing this. This is my buddy's 03 edge with a 3.0 automatic. When you turn the A/C on, you hear the compressor kick on, then kick off, then kick on, then kick off, and so on. It only does this when you are sitting still. I checked the pressure in the a/c system, and it is dead center of the "filled" section.

 

[Rearanger]

"idles irradict (sp?)" http://dictionary.reference.com/ :>)

I'd first check the belt tension and belt for slippage. Could be bad pressure switch, clutch relay, clutch, revolution sensor, thermister, ampifier; there may also be a temp switch that is designed to cancel the A/C if the engine gets too hot. You'll just have to check the components and connections one by one. You can run a jumper on the pressure switch connector to cancel that out and see if it still cuts in and out. You can also run a 12v wire to the clutch and engage it directly to see if it's the clutch. You can also bench test the relay. Usually an volt/OHM meter will test most of the components.

 

[Josh40601]

"idles irradict (sp?)" http://dictionary.reference.com/ :>)

I'd first check the belt tension and belt for slippage. Could be bad pressure switch, clutch relay, clutch, revolution sensor, thermister, ampifier; there may also be a temp switch that is designed to cancel the A/C if the engine gets too hot. You'll just have to check the components and connections one by one. You can run a jumper on the pressure switch connector to cancel that out and see if it still cuts in and out. You can also run a 12v wire to the clutch and engage it directly to see if it's the clutch. You can also bench test the relay. Usually an volt/OHM meter will test most of the components.

Everything was working fine one day, the next day it starts this crap. I'm not too savvy when it comes to troubleshooting engine problems, plus I have no idea what the hell half of what you said is, so i think its time to take a trip to the stealership

 

[James86]

What is the time between engage/disengage cycles? Mine does this as well, and its noticable at idle. If it's blowing cold air, it should be OK I would think. The clutch cycles for fuel economy and both my 99 3.0 auto and my friend's 98 3.0 auto do this as well, on A/C as well as defrost.

 

[Earl43P]

^^^ What he said, plus.....

The IAC may need cleaned, it controls idle.

The compressor cycling could mean it's low on refrigerant. If you know where the cycling switch is (on a line near the receiver dryer which is an aluminum canister plumbed in the AC line), simply remove its connector and use a paper clip to jumper the two sockets in that connector. It should no longer cycle the compressor clutch with the jumper installed. Insulate that jumper from shorting to the truck!

If that is the case, it may need just a bit more refrigerant, especially if it hasn't been serviced in a while.

The Haynes manual has some good servicing instructions...do not just "add a can" because you'll most likely add way more than it needs, creating a worse problem.

IMO, the best way to DIY top it off is using a thermometer with the cycling switch connector jumpered. When the temp stops dropping, quit adding! Add refrigerant at 1500-2000 rpm. Duct temp should get into the 40's. Duct temp should be even colder driving at 45mph, if warmer - you added too much.

 

[Josh40601]

I will try that stuff when i get back home. The time between cycles is about 15-30 seconds.

 

[Josh40601]

I reset the computer last night, and now it works fine. weird....