The air conditiong in my 1988 Vanden Plas gets warmer when the car is at idle. So much warmer that it is uncomfortable. The condenser fan is operating when at idle, and there is no debris blocking air flow. The system appears to be fully charged with freon, as it won't allow more freon in. I've recently had a new compressor installed. What could be causing the problem?

 

Monitor the pressure differential (low side vs high side) and see if the low side pressure climbs significantly at idle.
Could be a faulty or inefficient compressor or expansion valve issue?

bob

 

Thanks. I will take it to an A/C specialist and have them check the compressor and expansion valve. I live in Florida where the temps now are constantly above 90°.

 

Hi Ernest,

If your system will not inhale any more refrigerant, it is probably overcharged. It is very difficult to charge a system properly by pressure alone even with a good manifold gauge set, especially in hot, humid weather. Trying to judge the charge with a single-gauge can is virtually impossible and it's very easy to overcharge the system.

An A/C specialist will probably evacuate the system, then add back the correct refrigerant charge by weight along with an appropriate amount of new oil. Once you know your refrigerant charge is correct, you can determine whether other issues may be affecting your cooling, such as a problem with one of the pressure switches, temperature sensors, or the heater control valve being stuck in the open position or a blend flap being stuck in the position that feeds air through the heater core even when you want maximum cooling.

Please keep us informed.

Cheers,

Don

 

What year is your car? Quite possible that you car was not fitted with a hot water shut-off valve ...cars like this are often a bit hot

Some owners with the valve delete (guessing 91-92MY cars; not sure) clamp the hot water hose during summer.

Worth checking to see if you have a valve fitted.

Larry

 

Agreed.
The coolant control valve can be added as the vacuum solenoid is present in the climate control solenoid bock on either side of the gearbox tunnel.

I have added a RED vacuum line to the proper actuator on the left side of the gearbox tunnel and fitted a 'heater-control-valve' to the 1990-1992 XJ40.

The 'electrics' are there but the vacuum line is deleted.

bob

 

I just noticed you said it was an '88 so you probably DO have the valve.

Good idea to add model and VIN to your signature though ..

Larry

 

Don is absolutely correct about the system potentially being overcharged. The cooling performance will drop rapidly once the design charge weight is exceeded. Is your system unconverted, and still running R12, or has it been converted to R134a (more likely)? If it's still R12, you may be able to tell the state of charge using the sight glass on the receiver/dryer bottle. Once the system is full, there will be no bubbles in the sight glass with the system running at steady state. If it's been converted to R134a, the sight glass is not a reliable indicator of refrigerant charge level.

Any competent shop that does A/C repairs should be able to hook up a set of manifold gauges and check your pressures and delivery air temperature to a performance chart. A dirty/restricted condenser or evaporator, clogged expansion valve, too little/too much refrigerant, or moisture in the system can all lead to performance issues.

Many of these cars have been converted to R134a without replacing the compressor front seal, which was not compatible with R134a and can be a potential leak point. Same for the original R12 refrigerant hoses in the car, which were designed for the much larger molecule size of R12. R134a is a much smaller molecule and can leak out of original non-barrier R12 hoses.

As an aside, my '92 has the valve deleted, but as stated above, the vacuum solenoid is in fact there and functional, just capped. I am thinking about adding it to my car as it's a relatively simple affair due to the placement of the valve directly in the heater hose. Later cars 93+ had a slightly more complex arrangement. Thank you for the info about the correct color of the vacuum hose, Motorcarman. Any info on where it's supposed to be routed through the firewall?

-Nic

 

Thanks for all the replies.
It took it to a Jaguar Specialist and he diagnosed it as a defective solenoid not recirculating cold air back into the cabin. Cold air was escaping from the outside vent beneath the windshield wiper on the driver side. He has the part on order, and will install it next week.
I will give an update after testing it out on hot days.

 

Thanks for the update, Ernest!

I've repaired a bunch of those solenoids because I didn't know they could still be purchased. If you can find out where your mechanic is sourcing one from, please post it here. It will no doubt help other members in the future.

Cheers,

Don

 

Excellent! Glad to hear the issue is tracked down. A properly functioning recirculation mode is definitely a requirement for certain conditions. I can usually tell when my recirculation flaps are on and off due to the change in air velocity, and a slight whistle from the vents when the recirc flaps are moving.

It's a shame our early cars don't have a manual override switch like 93+ cars do, but I guess that's the trade off for having that novel humidity control feature! I've thought about looking into the possibility of adding a manual switch on the panel that could trigger the recirc solenoid directly.

Keep us updated!

Nick

 

Repaired and cold as ever. Here's what the trouble ended up being. The Jag specialist at first thought it was a defective solenoid not activating the recirculation flaps. It turned out not to be that solenoid, but the adjacent solenoid. After performing a vacuum leak test he found that it was leaking because the vacuum connections for the heater valve (Red and Yellow lines) were broken. He replaced the lines with new longer vacuum hoses, and vola! my A/C was back in business. Thoroughbred Motor Cars Salvage in Sarasota, Florida 34234 is where he sourced the solenoid.
Here are diagrams showing what he replaced:

 

Don,
The solenoid was sourced from: Thoroughbred Motor Cars Salvage in Sarasota, Florida 34234