i am having to a/c cut out in texas heat and i notice the fan not coming on , so i pull the low speed relay and it comes on at low speed , put it back in and it turns off , pull the hi speed and it comes on at low speed , and when i put that one back it rev's to high speed then off. so i am wondering what sensor is bad ?
as long as the fan is running my a/c is cooling like it should

any ideas ?


this is on my 05

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05 liberty CRD Limited - suncoast TC , GDE Turbo , GDE TCM Tune 2gen OEM filter head, stant 195 tsat, Autoandart Window Fix, New TB kit ~190k (Geordi)
06 Liberty CRD Limited - stant 195 tstat Autoandart Window Fix, 2gen OEM filter head, New TB kit ~180k (Geordi), GDE Turbo, GDE TCM ECO tune

No sensor is bad, that is exactly what the fan is supposed to do. The electric fan is controlled by the computer, based on the high pressure limit switch on the AC lines over on the driver's side of the engine. Follow that high pressure line from where it crosses the top of the radiator toward the alternator, the sensor switch will be on the pipe just under the alternator area.

The other limit switch is the low pressure switch, on the evaporator drier canister on the firewall by the passenger fender. Either one of these switches failing will make your AC not work at all - If it IS working part of the time, then more likely you have a low R134 level in the system. The first thing to do is a pressure test of the system with the AC on in the max cooling setting and the fan (interior) at high. Check the low side pressure, if the outside air is 90 or so, the low side should be around 35psi while the compressor is running. If it is lower than 20, ESPECIALLY in high ambient temperatures... Your system needs more R134. With low side pressure below 15 or 10, the low switch will cut out, causing your compressor to cycle constantly - This is very bad for the compressor clutch.

You can see the "acceptable" range for low side pressure on these convenient gauges mounted to the cans of R134 at your local parts hut. I prefer using the Arctic Freeze (blue can) of R134, and the gauge will have a set of numbers for the "ambient temperature" and a little rotating window with an arrow that creates a zone of pressure range. Rotate the window so that the arrow points at the ambient temperature, and the "zone" between those two markers is where the pressure should read while the system is running.

This will make more sense if you can see the can, I'm describing all this from memory.

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i have gauges , i will check again

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05 liberty CRD Limited - suncoast TC , GDE Turbo , GDE TCM Tune 2gen OEM filter head, stant 195 tsat, Autoandart Window Fix, New TB kit ~190k (Geordi)
06 Liberty CRD Limited - stant 195 tstat Autoandart Window Fix, 2gen OEM filter head, New TB kit ~180k (Geordi), GDE Turbo, GDE TCM ECO tune