196

Hi there I own 1996 XJ RHD in Australia, I have read as many posts and FSM pdfs as possible but the technical issue my XJ has is still causing no Air conditioning.

- Replaced Compressor with new Sanden unit from US.
- New Condenser
- New RX dryer
- New HI/LOW Px switch
- New Expansion Valve
- One Hose was repaired - small leak in rubber section on pressure leak down test.

the system was found to have a leak when I first purchased the XJ, had it evacuated - replaced then refilled, system would run cold for 2-3mins then not engage the Compressor, followed the
advice of the mechanic and he replaced the compressor - however same fault continued, would run until 2-3mins then not engage clutch.

The quotes from 2 HVAC auto guys made it uneconomical for me to proceed so I thought Id replace what I could and ordered the rest from Rockauto to replace original components from 1996 +new o rings and had it leak tested and refilled - It ran for about 10mins at idle (cool ambient OAT) and then does the same cut out.

Now that the weather here is 40degreesC it runs for even shorter 2mins then cuts out?

I have tried diagnostics by checking for continuity at the pressure switch on the RX dryer which it has, and 12v on the plug going to rx dryer, which also passes. However when I try to jumper the lead the compressor will not engage. The compressor will cycle ON-OFF quite happily on cool ambient temps at idle - but cuts out once you drive for 2-3mins.
the only component I have left to replace using my unsophisticated method of repair is the Evaporator, which I checked by removing the Blower and it was in excellent condition with no debris or mould in fins.

Its got me stuffed - when it runs the Expansion Valve is very cold and sweating (not iced up) and the air at the outlets is 3-4 degrees C.
The electric radiator fan blows when AC selected on and I have a new viscous fan clutch on the rad fan. The decal on the radiator mentions 907grams of R134, which it has been recharged with by the last air cond mechanic.

What should we check next, it would appear some other condition other than the hi/low psi switch is stoping the clutch engaging. I have no gauges.

awg

I also have a '96 in Australia, and have repaired my A/C system

in the circuit diagram there is an "A/C cycling switch" if that hasnt been replaced, I would, also swap the relay

The PCM is involved in controlling the A/C system

presume you have had it checked with gauges by pro when refilled and it was within parameters ?

I once installed a new expansion valve and it was faulty out of the box, my autolec had to order another one for me when I took it down to get gassed

pretty hard if you dont have gauges

196

Ok thanks mate I will look for the “A/C cycling switch" this may be it because it has no 12v power to the compressor once the car gets hot.
Is it under dash requiring a dash pull out I presume? If you have a part number please let me know...

My fridges auto lec is from the mining industry and uses the latest digital meters and did a comprehensive leak test with some gas that pressurised the system for 15mins with no loss. He filled it and it ran ice cold for the 10mins after cycling off and on but it was a typical 24degree day here, on his digital gauges you could see the temp of the gas.
he was my third technician I’ve used after the rest just want to charge more than the vehicle is worth, I am $2000 into it so far and am convinced it can be repaired,

We have swapped all the relays around, but I really need to have some idea of where to direct a fridgey autolec on $100 an hour.

196

I re read abovetimberline’s HVAC guide here on the forum and noted:

temperature sending unit can also cause the a/c to not operate,if it is giving a false reading or the sending unit is replaced with the wrong one the system will think the engine coolant is hot and will not allow the system to operate,the system does this because any added heat to the air coming into the radiator will cause poor heat transfer in the radiator.

so I’ve removed the Coolant temp sensor From the thermostat housing replaced it with a spare from my sons 2001 xj and taped the existing sensor in free air, ran the vehicle for 1 hour driving and idling in 30c temps tonight without the ac compressor failing to re engage. I’ll order a new coolant temp sensor From rockauto and see if this helps after testing it tomorrow with hotter weather. Anyway this is the longest I have been able to have correct operation of the AC compressor.

awg

That is a plausible theory.

To my knowledge, in at least some modern vehicles, if they become too hot engine coolant wise, the A/C will not engage

I thought that may be a result of the 3 way switch, but it may be the PCM will not engage the compressor clutch when it has an overheat indication

and Yes..A/C is a MUST here...its pretty hard to get hold of a RH condensor,

RH hoses need to be custom made, and Lord only knows where to get a RH evaporator

4.3L XJ

First thing to check is the low pressure safety switch. Make sure it passes current to the compressor. It is located on the left hand drive models on the accumulator. You can test it by unplugging it and putting a paper clip in both sides of the plug. If that is the culprit, then easy to replace, but you will have to evacuate the system to do it. There is also a high pressure cut out switch, located in the HVAC housing on the left hand models, not sure about right hand drive. One other thing to consider is that you might not have enough refrigerant in it. If so, it will ice up and may cut off the compressor till it thaws due to the high pressure switch.

196

Thanks all those components including hi/low PX switch replaced with new and checked by hvac autolec tech.

The fault has been narrowed to some issue with the coolant temp sensor on the thermostat housing, I’ve just been driving this morning in high ambient temperature and the AC is functioning correctly, with compressor cycling and no issues, whereas previously the AC compressor would not engage once the vehicle reached And stabilised at operating temp 95deg C.

I have a new stant 74043 on the way from US now. Will report back on how it goes.

196

fortunately the condenser is easily flipped with the brackets on the LHD model I sourced from RA.

awg

thats good to know. I saw about 3 or 4 bad used ones before I got a good one, (and 2 bad compressors)

think I read the LH evaporator can also be adapted to fit RH, but that seems suspect

a new RH condensor was available for $A440, the compressor is even more, so Rock Auto might be the go

4.3L XJ

I would be interested to see what happens to your high and low side pressures when it quits

196

It’s ran for two days now in the heat 36+c AC continues to work, at idle is a touch warmer without ram airflow over Condenser. I’ll get the hvac tech to throw the gauges on next time I have him around and report the Hi/Low pressures If it quits again.


awg we sourced a new sanden compressor locally from a Chrysler specialist shop cost me $1000 fitted, every other supplier could only offer me Chinese knockoffs, and I was very hesitant to order AC from US myself given the difference between LHD. The new condenser was a standard LHd model and we just flipped the brackets, it was substantially less than the new ones I found list in AU. Even radiators have been

awg

A set of gauges is nearly worth buying

learning to interpret them is another thing

I downloaded material that is for training auto A/C techs that helped me a lot with A/C work

The RH Ebay radiators over here are pretty abundant & cheap. Chinese knock-offs of course

keep us updated on your progress...I believe from what you have said that the engine coolant temp sender to the PCM is sending an incorrect signal

If this is the case, the PCM may respond by shutting off supply

Have you ohmed out the sensor...specs are in the FSM somewhere I am pretty sure

I have the Electrical Chapter of '96 FSM

196

Thanks, the engine coolant sensor is showing 2.0ohms on the 20k scale, at normal temp. I will go and look for the electrical FSM specs now. I I used the the 96FSM last night to instal a compustar remote start, remote lock system.

196

Replaced the Coolant sensor with the correct Stant part from Rockauto, have had zero issues for last week, driving on freeway to extended idling no issues. I could have saved myself almost $1500 by just replacing this coolant sensor. The Stant sensor has a significantly smaller diameter probe. The sensor it replaced was recently replaced by P.O. mechanic and has no part numbers. Its great having AC on the freeway with 104F here today in Perth.

awg

good to have a new compressor and condensor as they let go eventually anyway

you have a '96 ?...was it the sensor at the rear of engine, or front I think you said ?

The Chinese repro parts are very unreliable

I have acquired as many as I can used OEM sensors from a couple of Jeep Nuts who sold their stash, luckily they had '96, so the sensor plugs exactly match