As my 3rd summer approaches as a JK owner, I knew it was time for me to solve my A/C issues. My A/C always seemed OK, but never really good. It hit 100F in Phoenix yesterday, so I decided it was time to get moving on this project. The Jeep sat in the sun all day and I got in around 1800 to drive home. I noticed it was cool inside, but I wasn't as comfortable as I could be. After doing some reach, I found the following. I did not figure this out myself, just posting a "how-to" on information I found before.
Here's my temperature last night at 1900 after ~45 minutes of driving on the freeway at ~100F outside.
72...72?! That's pathetic and not cutting it in my book. I measured this temp inside the vent port of the center dash using a thermocouple.
It seems that the JK uses a thermistor inside the dash that taps into the airbox behind the A/C controls This thermistor controls when the compressor kicks on and off to reach the temperature the driver wants based off of the cabin temp. Apparently they have accuracy issues from what I've read. Removing the thermistor itself breaks it as it is a one time use connector.
If you follow the thermistor connector (by the gas pedal, sticking out horizontally) you'll go up about 6 inches and find the connector on the side of the airbox, pull it off and disconnect it. The plug is white with gray insulated wires heading up towards the radio.
I made a jumper using a 22K ohm 1/5 watt resistor (5 pack at Radio Shack is $1.49 + tax, item number 2711339).
Here's the jumper I made. (I know, not the best solder job as I was in a hurry)
Here it is with heat shrink installed. I ran a continuity check after to make sure it was all good.
Installed on the plug going to the thermistor (sorry it's a bit blurry, but you get the idea)
Temperature reading the following morning after getting the dash back together. This was at around 0700, ~72F outside.
Conclusion: The ambient temperature outside is certainly different between the As Found and As Left readings, but I can tell the A/C is much colder now. Yes this causes the compressor to stay on. I don't see an issue with it myself as running it full time seems better that constantly going on and off. For those of you in more humid climates: going too cold may cause you to ice up the system. It can thaw out and work again just fine, so just be aware. I have heard of many people doing this for a year or so and are very happy. Again, I didn't come up with this, just doing a write-up with my own photos.