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Unread 06-04-2013, 02:52 PM   #1
carywhunter
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2002 KJ Liberty 
 
Join Date: Oct 2012
Location: Santa Fe, NM
Posts: 6
Electric Radiator Fan Causes A/C to Rapid Cycle

Really confused here.............Original problem.......02 Liberty Renegade 3.7 with tow package, 130k would overheat at idle or stop n go traffic ONLY when AC was running. During this time you could hear the AC clutch rapidly engaging -disengaging every few seconds. AC would work for 5-10 minutes then start blowing warm air as engine temp gauge would rapidly rise........But all you had to do to bring engine temp back down to normal was turn off AC.........electric fan was spinning strong any time AC was on and coolant was clean and correct level........ Because of tow package it also has fan clutch which seemed the possible weak link.......Went ahead and replaced fan clutch along with water pump and installed fail safe 195* T-stat.......radiator cap only a few months old. Put it all back together, burped the coolant, started up and cranked the AC. Drove around at low speed with AC blasting ice cold working better than ever and engine never even thought about overheating. Even let it idle in park for half hour with AC on and it stayed ice cold with engine temp in perfect range. Overheating issue solved....However......As I was proudly observing the fine functioning fruits of my labor I realized that I had failed to plug the electric fan back in when I put things back together and notwithstanding ........ice cold AC and perfect engine temp. Went ahead and plugged it back in..... started engine n turned on AC. Elec fan blowing as it should but almost immediately the AC clutch started its rapid cycling and quit blowing cold. Engine did not start overheating as in the past so that's good but why would electric fan that comes on as it should when AC is turned on cause compressor to rapid cycle and basically not work. Once I unplugged electric fan the AC clutch once again stayed engaged for much longer intervals as it should and worked great. Elec fan works-seems if relay for fan was bad it wouldn't turn on but in any case should only affect the fan..... AC compressor relay????? If it was faulty why would it work fine unless the elec fan (which is suppose to help it) is plugged in?? Tempted to just leave elec fan unplugged since I have no issues without it but I know it's there for a reason..... And hotter months are coming. What am I missing? Thx

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Unread 06-04-2013, 06:13 PM   #2
streetglideok
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2005 KJ Liberty 
 
Join Date: Jul 2011
Location: Colorado Springs, Colorado
Posts: 2,456
Cant really condemn anything until you have pressure readings of high and low side of the a/c system. It sounds more like your system is undercharged, or tainted with air/moisture, and with the increased air across the condenser, the compressor cycles more often due to low side pressures being lower. Whole thing sounds funny, but without those readings, you're speculating. I would have a hard time believing the fan is making your a/c not work. I think you are seeing a symptom of a problem, not the cause.
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Unread 06-04-2013, 09:15 PM   #3
carywhunter
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2002 KJ Liberty 
 
Join Date: Oct 2012
Location: Santa Fe, NM
Posts: 6
At the moment I only have a small gauge for the low pressure side. Engine off its goes past 120 psi. AC running and cooling well it hovers around 45 with outside temp of 80 and air coming off fan shroud about 155-160 but when I plug in the fan pressure quickly shoots up to 80psi compressor goes off. Pressure continues to about 100psi and clutch re-engages for a couple seconds as pressure drops to 80 then compressor off for a couple seconds as pressure climbs to 100 then on for a couple seconds as pressure drops to 80 etc. during this 80 to 100 psi back and forth air is not cooling.
Thank you so much for responding earlier. I appreciate any input
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Unread 06-04-2013, 11:03 PM   #4
streetglideok
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2005 KJ Liberty 
 
Join Date: Jul 2011
Location: Colorado Springs, Colorado
Posts: 2,456
Something is wrong. 35-45psi is what you would typically see on the low side. Running the electric fan, which is the primary fan(mechanical fan is secondary), pressures should be lower. No one has tampered with the wiring of the fan have they? Was the fan replaced at one time? Which way is the air moving from the fan? Either note the rotation of the electric fan and the orientation of the blades, or remove the mechanical fan and turn the system on to verify.
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Unread 06-05-2013, 12:21 AM   #5
carywhunter
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2002 KJ Liberty 
 
Join Date: Oct 2012
Location: Santa Fe, NM
Posts: 6
Pressure was a bit high according to specs so safely relieved some pressure which now stays between 20 and 30 psi at 78 degree ambient at idle. Pressure will slowly lower to 20psi and compressor will kick off for about 8 seconds as pressure goes back up to 30psi and compressor kicks back on for about a minute as pressure slowly drops to 20 etc. seems like a fairly normal cycle and center console temp steadies at 41 degrees. Perfect. But the second the electric fan is plugged in it goes back to 100 psi off 80 psi on every 3 seconds cycle and stops cooling. Fan was replaced 18 months ago by previous owners mechanic. Jumped it off battery with engine off and airflow is definitely front to back-outside of engine compartment toward inside of engine compartment. Even started up and ran AC checking pressures with fan jumped to rule out other electrical interference. Exact same results. I don't know enough about AC to say but it almost seems like the combined airflow of the two fans over the condensor is too much which makes no sense at all. Also don't see how it could be electrical since I had same results with the fan powered directly from the battery. ???????????????????WTF
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Unread 06-05-2013, 08:07 AM   #6
streetglideok
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2005 KJ Liberty 
 
Join Date: Jul 2011
Location: Colorado Springs, Colorado
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You have another issue like I said. There is no such thing as too much air across the condenser. They need as much as they can get. Without seeing all the pressures and the vehicle in person, its merely guessing.
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Unread 07-16-2013, 06:20 PM   #7
billb2011
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1999 XJ Cherokee 
 
Join Date: Jul 2011
Location: Minford, OH
Posts: 172
Did you ever figure out this problem. I am having an identical problem. Exactly as you say, driving down the road the a/c works great. Stop in traffic or at idle the a/c compressor begins to short cycle, and the jeep starts to overheat. Even when the jeep is cold I can start it and let it idle and the a/c short cycles immediately. I thought it had to do with the cooling system because it is over heating, but the compressor short cycles even when the jeep is cold and the electric fan hasn't even come on yet.

Any ideas? What would be the first thing I should look at when the jeep is overheating at idle? The fan is working and it only starts to overheat when the a/c is on, turn it off and the temp comes back down.

Thanks.
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Unread 07-16-2013, 08:32 PM   #8
streetglideok
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2005 KJ Liberty 
 
Join Date: Jul 2011
Location: Colorado Springs, Colorado
Posts: 2,456
Quote:
Originally Posted by billb2011 View Post
Did you ever figure out this problem. I am having an identical problem. Exactly as you say, driving down the road the a/c works great. Stop in traffic or at idle the a/c compressor begins to short cycle, and the jeep starts to overheat. Even when the jeep is cold I can start it and let it idle and the a/c short cycles immediately. I thought it had to do with the cooling system because it is over heating, but the compressor short cycles even when the jeep is cold and the electric fan hasn't even come on yet.

Any ideas? What would be the first thing I should look at when the jeep is overheating at idle? The fan is working and it only starts to overheat when the a/c is on, turn it off and the temp comes back down.

Thanks.
Need to address the cooling fan issue first. Without knowing the year of your jeep, I can't give you specifics, but if the electric fan has 3 wires at the connector, it is a two speed fan, and it sounds like one speed is gone. Once your cooling system is working fine, then you can address the a/c issue, which could be an undercharge issue and would require an evac and recharge. If you ignore the cooling issue, you'll just need an engine, not just a/c.
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