Low side and high side A/C pressure switches

Bammo68

TJ Enthusiast
Joined
Dec 27, 2021
Messages
160
Location
Western Australia
OK - dumb question of the day. '99 TJ without Aircon - this is part of my ongoing quest to retrofit AC (aka the Junkyard AC project). I've got two pressure switches in the system - one that sits between the compressor and the condensor as shown in red and one that sits on the input to the receiver/drier (so it sits on the output of the compressor). The guys who made up a custom line for that compressor-receiver drier butchered the pressure transducer and I need to replace it. Luckily I have a spare but I dont know if the two switches are interchangeable - is there a high pressure switch and a low pressure switch on the system but they are both the same switch or are the calibrated differently?

Bonus question: are the switches likely to have been changed between TJ model years and even Cherokee models of similar vintage? There is no way for me to tell what model they came out of and all of them appear to be plug interchangeable.

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I think the one in red is the low side switch and green is high side


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High and low pressure switches are different. Low pressure switch should be the same across model lines.
 
How can I tell the difference? Both appear to look the same (at least the ones I have in front of me) and there is only one type of AC pressure switch listed in the RockAuto catalog? There is nothing in the Parts Manual for the TJ.
 
Flow goes from compressor to condenser to orifice to evaporator to accumulator/dryer then back to compressor. So the one between compressor and condenser is the high pressure switch and is on the outlet/discharge side of the compressor; the one at the dryer is in the inlet/suction side and is the low pressure.

They are definitely different. The high pressure switch changes state at a couple hundred psi higher than the low.

The parts manual for your year is posted in the Resources subforum and might be helpful finding the correct part.
 
How can I tell the difference? Both appear to look the same (at least the ones I have in front of me) and there is only one type of AC pressure switch listed in the RockAuto catalog? There is nothing in the Parts Manual for the TJ.

If they appear the same look at the fitting size it should be different. Check the connector. The index tab ( the 3 black tabs that stick out on the outside) will be in a different position. They may have pressure specs on them low 22-48 psi, high 250-350 psi.
 
The Parts Manual was the first place I went but its useless for this. It only shows a part number for the low pressure switch at the drier. It doesn't show whether there is even a connector on the high side. JeepAir list that low pressure switch under a totally different name so I wonder if that is why there are so many different forum questions on this and other Jeep forums asking for help! Its not a particularly easy question to answer!

The parts manual for your year is posted in the Resources subforum and might be helpful finding the correct part.

The photo's in the OG post above are not of my Jeep - they are of a RHD '99 that happened to be at the dealership and I took the opportunity to photograph the heck out of the factory setup!
 
OK Update time for those following along at home.

There is definitely a different high side and low side sensor as @NskLJ and @freedom_in_4low pointedly told me! Upon closer inspection and actually attempting to connect the connectors to the sensors yes, the Low Side sensor has a positioning fin in the centre of the housing whereas the High Side has that slightly offset. I have 2 high side sensors and 1 low side sensor in my collection of bits from the wreckers. The single low side sensor I have was destroyed by the hose company (figures) so will order a new one of these. Hopefully this post helps others in the same situation as me @TJ Starting

RockAuto call this a "Clutch Cycling Switch" and it comes under the electrical connectors section of their catalog and not the HVAC section for some reason (Part # 20922) - so if you go looking for AC Low Pressure you wont find it.

The other part (e.g. #20925) is listed under High Pressure A/C Switch

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