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Jaguar doesn't cool

aussiejag on Sat February 02, 2008 11:22 PM User is offlineView users profile

Year: 1980
Make: Jaguar
Model: XJS V12
Engine Size: 5.3L
Refrigerant Type: R134
Ambient Temp: 30C
Pressure Low: 5-20
Pressure High: 160-200
Country of Origin: Australia

My 1980 Jag aircon has never really worked in the 7 years I have had the car. Last year I had the compressor, condenser, evaporator and TEV replaced, but the best it could do was a vent temp of about 15C and a return pipe to compressor temp barely ably to achieve condensation.

I have just acquired an aircon test set which allows me to measure pressures.

Static pressure 100 PSI

High side 165 PSI
Low side 20 PSI

High Side 190 PSI
Low side 5 PSI; difficult to get accurately at the very bottom of the gauge scale, but just off zero.

High Side 140 PSI
Low side 85 PSI
After about 15 minutes, the low side has risen to 100 PSI over a few minutes and the high side has crept very slowly down to 100 PSI

I tried adding hot water to the capilliary on the TEV, but it is very difficult as the TEV is between the engine and the firewall.
No obvious effect at idle
Sped up the equalisation of pressures after shut-down, but not much.

Pressures on high and low sides are similar to above. The Low side pressures are a few (
The discharge pipe from the compressor is very hot, much too hot to touch; close to 100C I think. The pipe leaving the condenser to the TEV is warm to touch; I guess between 40 and 50C.
The return to the compressor is cooler than hand temp, but rarely cold enough to condense water from the air. At best, perhaps 15-20C.

The cooling is best on cold startup when the condenser is cold. Condenser has both the airflow from the mechanical and electric radiator fans and an extra electric fan in front of it.

My thought is that there is an almost total blockage between the condenser ant the return to the compressor, which may, or may not be associated with the TEV, which means there is very little flow of refrigerant round the circuit.

WHAT DO THE EXPERTS THINK? Problem and solution



Chick on Sun February 03, 2008 6:48 AM User is offlineView users profile

Are you using R12? or an R12 replacement? Did you change the drier? Is the suction line back to the compressor cold? Is the temp into and out of the drier the same?

Email: Chick


Freedoms just another word for nothing left to lose

aussiejag on Sun February 03, 2008 4:19 PM User is offlineView users profile

The refrigerant is R134. The car was converted from R12 seven years ago. R12 is no longer legal anywhere in Australia. The A/c service who did the conversion put a sticker on which says R134, not R134a.
Yes, the drier was replaced last year when the other components were replaced and the refrigerant circuit has not been opened since.
The temperature on either side of the drier is the same as far as I can determine by hand.
The suction line back to the compressor is what I referred to as the return; It is cooler than any other part of the cold circuit, but not cool enough to condense water from the air; I guess around 15 to 20C.

I will try to measure some temperatures


aussiejag on Sun February 03, 2008 7:28 PM User is offlineView users profile

I measured the temperatures today after I returned from a 30 minute drive; hence engine and aircon temperatures stabilised. I used the temperature probe which is part of my digital multimeter, so I guess +/-1 C accuracy. Readings were repeatable.

Ambient temperature 24 C = 75.2 F
Air vent temperature into car 23 C = 73 F
Discharge from Compressor 70 C (158 F) idle, 72 C (161.6 F) at 2000 RPM
Into Condenser same as compressor discharge
Out of Condenser 37 C (98.6 F) idle, 39 C (102.2 F) at 2000 RPM
Into drier tube same as out of condenser
Out of drier tube same as into drier tube
On pipe leading to TEV same as out of drier tube
Out of TEV 25 C (77 F) idle and 26 C (78.8 F) at 2000 RPM
Suction side of compressor 26 C idle and 2000 RPM

The suction side reading is higher than it was a couple of weeks ago; then it felt slightly cool to the hand and the vent air was also a bit colder. I am surprised that the vent air temperature is slightly lower than the out of TEV temperature, but that is how it measured.

Thanks for your great site. This problem has baffled three air-conditioning service organisations (and cost me a fortune). I hope you can beat them.


Chick on Sun February 03, 2008 7:42 PM User is offlineView users profile

Only way to do this one is to recover the refrigerant, recharge the correct amount back in to a good vacuum and then do your tests. It "appears" you may have a leak and or poor air flow over the condenser. But since this is a retrofit, you have to start diagnosining with the correct charge to rule out leaks etc..
Follow these Vac/charge procedures and get the pressures and temps once it's recharged. You have to be sure there is good air flow over the condenser, and if you have electric fans, make sure they are working properly..If you have an engine driven fan, it may be time to change the clutch on it..Let us know what you find...

Email: Chick


Freedoms just another word for nothing left to lose

aussiejag on Sun February 03, 2008 9:48 PM User is offlineView users profile

Thanks for the response.

I do not have a vacuum pump, so will have to take it to an air-con service organisation to have the refrigerant recovered, the vacuum and re-charge done. They have been totally unsuccessful so far. I don't have much choice as I live in a small town.

I have re-checked the airflow through the condenser. In the portion not covered by the secondary electric fan it sucks a ribbon very rapidly up against the upstream side even when the ribbon starts 4 inches in front of the condenser without the supplementary electric radiator fan turned on and instantly when the electric radiator fan is turned on. In the portion covered by the condenser fan, a ribbon is instantly sucked towards the fan from even further away, so I think the airflow is high. The airflow is much higher than on my other vehicles.

The mechanical fan has a thermo-viscous clutch, but it is turning at pulley speed all the time. The 12 inch electric fan on the radiator and the 8-inch fan on the condenser are working fine and the edges of the gap (1inch) between the condenser and the radiator are closed with foam strips.

If I am going to have the system evacuated, should it be cleaned out and the flow paths checked throughout before it is evacuated and re-charged?

Should an aircon service organisation be able to test the TEV and evaporator performance separately from the compressor/condenser/drier performance?


Chick on Sun February 03, 2008 10:06 PM User is offlineView users profile

The problem is that those cars never cooled that great with R12 in them, and being a retrofit, hard to know what they did, or what needs to be done. Which is why I suggest starting from the beginning. The pressures aren't that bad, but could be higher with R134. It's going to be hard to tell the repair shop how to do it, but if you could get a vacuum pump and gauges we could walk you thru it.. If you can rent, borrow or buy a cheap vacuum pump you can follow the vac/charge procedures I listed above, and go very slowley and tweak the system yourself. Or you may have to find a "better" shop that is willing to spend time on it. The expansion valve bulb needs to be placed just right, and tight on the suction line and well insulated. Not seeing the car, it just sounds like you have a leak now, and/or air in the system.. After it's recharged watch performance and if it's good in the beginning and fades like it "appears" your saying, you have to find and fix the leak..

Email: Chick


Freedoms just another word for nothing left to lose

aussiejag on Sun February 03, 2008 10:25 PM User is offlineView users profile

Thanks again.
The aircon is not a retrofit except that some "original" components were replaced last year with new ones and the system was changed to R134 about 6 years ago. I will visit each of the local aircon people and see if one of them will be co-operative.


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