LOST JEEPS :: View topic - My AC is causing the Jeep to overheat.

For the past few days, I've had to drive through heavy traffic for work. I've noticed at idle with the AC on, when I'm stuck in traffic, the Jeep will run hot. The needle has gotten to the 3/4 mark on the gauge. Once I begin moving again, the jeep will cool down to the normal spot just left of center.

The last two days, I've driven home without using the AC and the Jeep did not run hot.

A few things to know about my Jeep.
I have ECO and trans tune from GDE.
This same problem happened once last year, but never again. I had the jeep checked for a head gasket, and it was fine then. I've had several grounded wire issues over the years due to rubbing of the harness, and one of the three dealerships/autoshops that worked on my wiring issue actually cut the entire auxiliary fan wire out without me knowing it until a few months ago. The plug from the wiring harness is still in the fan connector, but there are no wires going to the front of the vehicle that I can even trace to try and reconnect.

Currently, the AC works ONLY while driving. If I stop at a light, the air stops blowing cold, and the engine will drag as it engages the compressor. I'm assuming that this is part of the problem. Why would the AC cause the engine to work that much harder? Can anyone identify what the cause may be? Could it be as simple as adding freon to my system?

Thanks for your help.
Thanks for the help.

Author:	Big Montana [ Wed Jul 29, 2015 6:44 am ]
Post subject:	My AC is causing the Jeep to overheat.
For the past few days, I've had to drive through heavy traffic for work. I've noticed at idle with the AC on, when I'm stuck in traffic, the Jeep will run hot. The needle has gotten to the 3/4 mark on the gauge. Once I begin moving again, the jeep will cool down to the normal spot just left of center. The last two days, I've driven home without using the AC and the Jeep did not run hot. A few things to know about my Jeep. I have ECO and trans tune from GDE. This same problem happened once last year, but never again. I had the jeep checked for a head gasket, and it was fine then. I've had several grounded wire issues over the years due to rubbing of the harness, and one of the three dealerships/autoshops that worked on my wiring issue actually cut the entire auxiliary fan wire out without me knowing it until a few months ago. The plug from the wiring harness is still in the fan connector, but there are no wires going to the front of the vehicle that I can even trace to try and reconnect. Currently, the AC works ONLY while driving. If I stop at a light, the air stops blowing cold, and the engine will drag as it engages the compressor. I'm assuming that this is part of the problem. Why would the AC cause the engine to work that much harder? Can anyone identify what the cause may be? Could it be as simple as adding freon to my system? Thanks for your help. Thanks for the help.

Author:	bugnout [ Wed Jul 29, 2015 9:15 am ]
Post subject:	Re: My AC is causing the Jeep to overheat.
Sounds like you have no electric fan and if your mechanical fan clutch hasn't been replaced in a while no air moving from it either. The AC will definitely dump heat into the cooling system, but if your fans were running it should pull the temp out of the radiator. I don't know what could be causing dragging the engine at idle. Beside the compressor, could be the alternator. check for red dust under the center cap of the alt pulley. Thats an indicator the clutch is wearing.

Author:	taroo [ Wed Jul 29, 2015 9:18 am ]
Post subject:	Re: My AC is causing the Jeep to overheat.
AC does not cause overheating. Lack of cooling capability and capacity does. Something is keeping you from cooling adequately. I would replace the fan clutch first. Thermostat is probably week as well but they fail open so probably not the cause. Ensure the electric fan is working. Without proper air flow you will have all kinds of problems. Big Montana wrote: For the past few days, I've had to drive through heavy traffic for work. I've noticed at idle with the AC on, when I'm stuck in traffic, the Jeep will run hot. The needle has gotten to the 3/4 mark on the gauge. Once I begin moving again, the jeep will cool down to the normal spot just left of center. The last two days, I've driven home without using the AC and the Jeep did not run hot. A few things to know about my Jeep. I have ECO and trans tune from GDE. This same problem happened once last year, but never again. I had the jeep checked for a head gasket, and it was fine then. I've had several grounded wire issues over the years due to rubbing of the harness, and one of the three dealerships/autoshops that worked on my wiring issue actually cut the entire auxiliary fan wire out without me knowing it until a few months ago. The plug from the wiring harness is still in the fan connector, but there are no wires going to the front of the vehicle that I can even trace to try and reconnect. Currently, the AC works ONLY while driving. If I stop at a light, the air stops blowing cold, and the engine will drag as it engages the compressor. I'm assuming that this is part of the problem. Why would the AC cause the engine to work that much harder? Can anyone identify what the cause may be? Could it be as simple as adding freon to my system? Thanks for your help. Thanks for the help.

Author:	flash7210 [ Wed Jul 29, 2015 9:32 am ]
Post subject:	Re: My AC is causing the Jeep to overheat.
I suspect that your electric fan is not working. Simple test: Fire up the engine, turn on the A/C, go out the the front of the vehicle and listen for the fan to turn on. If the electric fan does not turn on, then that is your problem.

Author:	papaindigo [ Wed Jul 29, 2015 11:08 am ]
Post subject:	Re: My AC is causing the Jeep to overheat.
I suspect the fact that the wires to the electric fan (just behind grill) have been cut are at least partially related to both the overheating and the fact that your AC blows hot when idling at a stop as adequate airflow across the condenser is essential to AC performance. Someone who knows more about the KJ (not particularly CRD specific) electrical system will have weigh in but as I understand it the operation of that fan is controlled by the PCM which presumably gets signals from one or more sensors and then triggers one or both of the fan relays in the power distribution center. If that "logic" is correct then you should be able to rewire the fan by wiring directly from the appropriate wires out of the back of the power distribution center to the high and low speed fan relays. Exactly how is not within my knowledge base but looking at the plug on my electric fan I see 2 blue wires (don't know if one has a strip) and one black wire. I'd guess the blue wires are power and the black is ground.

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Author:	Big Montana [ Thu Jul 30, 2015 12:31 am ]
Post subject:	Re: My AC is causing the Jeep to overheat.
Thanks for the input guys. The fan clutch is original and it has 150k miles. I'll start there. I'll have to take the Jeep to a dealer to re-wire the electric fan in the front. There were several wire breaks repaired over the last three years, and it looks a little fishy under the hood. I'll look for the blue wires though and see if I can do it myself. If it's easy though I don't understand why some tech would cut the wires to the fan. I hadn't thought about the fact that the AC system generates a lot of heat that needs to be moved away from the engine by air.

Author:	papaindigo [ Thu Jul 30, 2015 9:55 am ]
Post subject:	Re: My AC is causing the Jeep to overheat.
If you have a good auto electric shop in the area check with them on wiring before dealer. In fact our dealers often use the local auto electric shop.

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