Hey guys,

Yesterday I did the jumper test on the A/C low pressure switch because my A/C compressor would not turn on. Once I jumped it, the compressor kicked on, and it instantly started blowing cold air. So I'm assuming that's the problem and I'm going to replace that sensor.

It looks like it should be pretty simple and straight forward, but I noticed, that in the service manual, it says something about how you need to lubricate the new sensor O-ring with some A/C oil. I don't know much of anything about A/C systems yet... But I'm thinking that it's a good time to learn, since the A/C quit working in my '06 Jeep Liberty CRD and in my '03 VW Jetta TDI. So I have two questions:

1. Has anyone replaced this switch? And do you really need to get A/C oil for the new O-ring? I've never heard of that before, so I don't know what that is. But like is said, I don't know too much about A/C in general, yet....

2. What do I need in order to properly diagnose and fix A/C issues in general? I don't have any A/C specific tools or pressure gauges or anything. I want to check the pressure on the high side and low side for my Jeep (and the Jetta). Do I just go to Autozone or something and ask them for A/C pressure gauges? Or do you just have to buy one of those re-charge kits that I've been seeing around? Those have a gauge on them, right? Do we have any A/C experts on this forum?

Thanks in advance for your help.

I replaced my switch recently.
I used a light amount of vaseline I keep in my tool box for orings just enough so the oring doesn't
catch and tear. I have not problems.
The switch is hard to get a wrench on but not all the tight.
I used a set of gauges to tell if the system was healthy.
Luckily it was and I did not need to evacuate the system and recharge.
Replacement of the switch is all I needed. Now my ac blows cold again.
good luck with the swap

You got that right.... I find that everything I do to my Jeep is much tougher to access compared to similar replacement jobs on my Jetta. They really just barely crammed everything in, in the engine compartment.

I replaced the low pressure switch last night. And sure enough, A/C works again...



I don't have a set of gauges, so I couldn't check the pressures... But it seems to be working well, just like it used to. I would like to double check the pressures though just to make sure they are good. So I may end up getting a set of gauges for myself.

Thanks for your insight.

If you have the gauges and know how to use them that's fine and critical if you open the system but absent gauges basic AC cooling performance can easily be checked with a hand held thermometer. See temps expected at the center vent vs. ambient temps in a chart form on page 24-4 of the 06 FSM. Do the test after car is FULLY cooled which takes about 10 miles on a really hot day at max. AC. When I last checked mine the readings were 45 and 48 at 75 and 95 (F) ambient respectively.

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Sold to LOST member my 05 Ltd, GDE Stg II turbo + TCM tune, SunCoast TC w. Transgo kit, Steiger window regulators, Samcos, Fumoto valve, 2nd gen filter head with Lub. Spec. bleeder, Hayden clutch & 11 blade fan, inverted spare, P-1 battery, BF Goodrich Long Trail TAs, Etecno1 glow plugs, timing belt at 50K miles/8 yrs

All you need to service your AC is a set of decent gauges (less than 100 bucks) and a decent vacuum pump (this may be around 300 bucks). There are a bunch of how-to's online on how to interpret the gauges and how charge the AC, I particularly like this one:

https://www.youtube.com/watch?v=lglPJuBXVeE&feature=kp

It's really not such a big deal, and you don't need to know a bunch of AC info, especially for basic work such as replacing compressors, evaporator, condenser, etc.

Edit: some solution to clean the condenser is not a bad idea something like Nu Calgon which is available online and is usually used by non-auto AC professionals.

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2005 kj CRD, samco, suncoast tc, provent, Kennedy lift pump, GDE ECO full torque, 2nd gen filter head, 245/70/16 a/t tires, mopar light bar, fumoto oil valve, OEM Skid Plates, ARB Front bumper and HD OME, tru cool LPD47391 40k GVW tranny cooler (stock cooler delete), FF Dynamics e-fan and shroud, rocker arms replaced, HDS2 190F thermostat.

It's funny that you happened to post that particular link. I just stumbled across that video yesterday as I was looking up more info on A/C systems. I really liked it too. Definitely taught me a lot about A/C.

Before you go replacing your LPS, you should check the ground wire associated with it. It is located on the passenger side of the engine bay down near a stack of 4 large connectors. If you do not have a good ground there, your clutch will not engage.

I found this out after reconnecting all the wiring on that side after replacing my head gasket.

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2006 Liberty CRD Limited

Provent @ 43,000 km
SEGR in progress
SAMCO Sport hoses @ 48500 km
Goodyear Wrangler Duratrac LT225/75R16