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Rough Idle Issues with AC

 
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  #1 (permalink)  
Old 02 Jun 2012, 09:47 am
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Default Rough Idle Issues with AC

My wife's 05 PT Cruiser idles rough only when the AC is on. As soon as you start the AC when parked or at a stop light it blows hot and the engine immediately starts running rough. It sort of cycles between about to stall and ramping up the RPM's to compensate. I checked last week after looking at this forum and the radiator fan turned on whenever the AC was on so I decided to clean out the IAC which didn't seem to help. I have time again this weekend to work on it so when I checked this morning, the fan wasn't coming on with the AC. Should I just replace the fan/motor or could it be another issue. As soon as you're at a good speed and the A/C is on, it blows cold and the engine does not seem to have problems. Any help would be great!
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Old 02 Jun 2012, 10:09 am
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Default Re: Rough Idle Issues with AC

Test the fan first. The outer pins are for power center is ground. Jumper the power to both pins one at a time, if it runs then check the connector for charing.
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Old 02 Jun 2012, 10:09 am
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Default Re: Rough Idle Issues with AC

Definitely sounds like the fan. I'd replace it and your problem will go away.

If you saw the fan turn on when the A/C was on, but now it's not, I'd bet the carbon brushes have worn down just enough to where you're getting intermittent success. Pretty soon it won't work at all, so it's best to just replace it now.
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Old 02 Jun 2012, 10:14 am
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Default Re: Rough Idle Issues with AC

Do I have to take out the whole radiator to replace the fan assembly?
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Old 02 Jun 2012, 10:22 am
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Default Re: Rough Idle Issues with AC

Quote:
Originally Posted by Busted_PT View Post
Test the fan first. The outer pins are for power center is ground. Jumper the power to both pins one at a time, if it runs then check the connector for charing.
I would not be comfortable doing this myself. Is there a cable that I can buy that does the same thing?
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Old 02 Jun 2012, 11:16 am
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Talking Re: Rough Idle Issues with AC

Quote:
Originally Posted by BlakeL View Post
Do I have to take out the whole radiator to replace the fan assembly?
No, not at all.
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Old 02 Jun 2012, 11:21 am
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Default Re: Rough Idle Issues with AC

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Originally Posted by BlakeL View Post
I would not be comfortable doing this myself. Is there a cable that I can buy that does the same thing?
NO. Pieces of wire laying around the house will do. But there is a scanner (OBDII) that the dealer or mechanics have that will test both speeds of the fan and other devices/sensors around the engine to help diagnose all kinds of problems.
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Old 02 Jun 2012, 11:35 am
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Default Re: Rough Idle Issues with AC

Quote:
Originally Posted by BlakeL View Post
I would not be comfortable doing this myself. Is there a cable that I can buy that does the same thing?
Quote:
Originally Posted by CREWZIN View Post
NO. Pieces of wire laying around the house will do. But there is a scanner (OBDII) that the dealer or mechanics have that will test both speeds of the fan and other devices/sensors around the engine to help diagnose all kinds of problems.
Just unplug it and run a ground to the center pin then touch the outer pins with 12v from your battery one at a time to see fan run. If only runs one side or none it's bad!!
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__________________________________________________ __________________________________________________ ___________Performance, Body and Service, OEM

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Old 02 Jun 2012, 08:24 pm
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Default Re: Rough Idle Issues with AC

Blake, there is a "How To" that Crewzin wrote up on how to change your radiator fan. You do NOT have to pull the radiator to do this job, and the pics and teachings of the "How To", make it a fairly easy fix.

Your problem (because of the symptoms you mentioned) indicate a very common issue with our PT's: the fan is not working up to snuff--and, so, not cooling your A/C "high side", via the condenser, while at idle. On the road, you actually need no fan--the air comes naturally when you're moving along at a decent speed, and that's why your A/C blows cool, then, and your engine stops sputtering.

By the way, stop turning on your A/C until you get this fixed. You can rupture A/C lines if you do, which will cost you lots and lots more money.

Tim
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Old 02 Jun 2012, 08:38 pm
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Default Re: Rough Idle Issues with AC

Blake, I forgot to mention another way to test the fan if you're "not comfortable" using the jumper wire trick.

Get a flashlight and mirror. Don't turn on your A/C. Take the car for a drive, heat up the motor to normal temp., pull over to an area where you won't get squashed by passers-by, put the car in Park or Neutral and put the brake on, open your hood, position the mirror so you can see the fan blades. Use the flashlight to see.

If the fan blades are not running at first, give it a few minutes to see if the low speed finally comes on as the engine idles. The noise will be very little--that is, if the fan blades start moving at low speed. If after a few minutes no fan, then your low speed is shot.

Go back to the inside of the car and turn on your A/C. Then go back and listen to the fan. It should be much louder (that's the high speed, kicking in). Forget looking for fan movement because if the fan is on high speed, the blades are moving too fast to see--and the increased whirring noise of the fan will tell you the high speed is working. Oh, your engine will probably act like it's going to die during this last test. Turn off your A/C.

If one of these fan speeds doesn't work, your fan is probably shot.

Tim
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