When I get in and start my car, the AC will not get cold or even cool while sitting and idling. It seem to be fine once I get moving. Something has changed as this did not used to be the case. I have owned the car for 7 years. Any theories on what the problem is?

 

When the radiator/condenser fan begins to fail, it may be intermittent or too slow for the AC but not slow enough to cause engine overheating.

After staring, raise the hood and check the temperature of the large refrigerant pipe adjacent to the fire wall. If it is cold right after starting, look at the fan.

If not cold, suspect a low refrigerant charge.

 

Loss of refrigerant is far, far more common than a fan going out. Cold air while moving but not while stationary is highly indicative of that, and if your car hasn't overheated, I wouldn't even bother thinking about the fan. Anyway, DO NOT use one of those quick charge R-134 cans they have at the auto parts store. Those things will introduce moisture and create a bubble in the refrigerant, so to speak, and either of those conditions demand professional service. The system will need to be evacuated and then put under vacuum to check for leaks, so you'll need to take it to an AC shop for any repairs. Be sure to mention that you'd like the Schrader valves replaced when they do their test. Those are the problem, or at least are a contributing factor to the problem, about 75% of the time, and are cheap and easy to replace. If the shop is worth their signage they'll replace them anyway, but it doesn't hurt to ask.

If you have good hearing, you can crack open the high and low port caps to listen for a short hiss. That will tell you that the Schraders are indeed leaking. It's not a loud noise, so you'll need to do it in your garage and with your ear close to the caps. You can also look at the view ports on your high and low sides for bubbles. Start the car, turn your AC on the coldest setting and watch for bubbles. You may need to use a flash light to get a good look. If you see any, that's definitely a low charge. If none of that makes sense, don't worry about it and just take it in because all that'd do in your case is give you a little FYI/gee whiz info.

 

The fan not coming on makes sense. I'm going to investigate that for sure. As for low refrigerant, it was topped off by a technician when I first noticed this last year. Of course still a possibility.

 

If the charge is low enough, the ac won't command the fan on, nor will it command your ac pump to engage, either.
When it was "topped off," did they evacuate the system and do a vacuum test for leaks, or did they just throw more in and say good enough?

 

Most "Mechanic Top Off"s are a guy with a can and a hose. Nothing checked, nothing changed.

 

The top off was at the Jaguar dealership. I trust them and believe it was done properly. Of course, if there is a small leak, some could have bleed off by now. But as I mentioned, the AC does work well when moving, so it's not totally dead. I always hesitate to mention that I go to the Jaguar dealer because of the parade of replies about paying to much, blah blah blah.

 

My initial thought was that I was up for a new compressor as the aircon when I purchased the car didn't blow icy cold.

I just got my air conditioning regas a few months ago by my trusted aircon guy. On the XKR the low pressure port is right behind firewall and you need to remove the inlet tubes to get access to the charge port.
He put a colour dye and tested for leaks and assume that the previous person didn't regas the system properly because the port is hard to reach without dismantling a few things and needing small hands.

 

Bring it here to the dealer I used once and only once. They don't have a problem charging you out the arsehole for work and recommending you do more so they can charge you more!

 

The 5.0L cars have a fairly well documented issue with the Direct Pressure Sensing valve in the compressor getting sticky and not letting enough refrigerant flow at low RPMs. That's why when you pickup the RPMs the refrigerant flows better and you get powerful A/C again. Unfortunately, the compressor has to be removed to change the valve, and then the system evacuated and recharged.

Mine has been doing this for years and I've lived with it so far. Being that I am in Canada, and my car is a convertible, I don't use the AC much...and when I do it's almost always on a highway trips, and it works fine then.

Details here:
https://jlr.oemdtc.com/69/inadequate...10-2016-jaguar

 

Replace the compressor. My car went the same way-- slowly but surely, it just wasn't as cool stuck in traffic on hot days.
I finally had it done and it cooled like a brand new car. Night-and-day difference. Lived with crappy A/C for way too long.

 

Safe to assume that a new compressor comes with a new DPS valve installed? If so, probably best to just to replace the compressor?

 

I had the same problem and with summer in Dubai approaching, I got it checked for leaks. Thankfully it was just the refrigerant and now it works absolutely fine even when its close to 40deg C outside

 

Yes, a new compressor would include a new DPS valve. I'd probably do the same, no point in going through all the effort of removing and re-installing a used compressor, better off spending a few hundred dollars more and putting in a brand new unit.

 

Ten-year-old car. No problem with AC when moving. Refrigerant topped off by dealer.
The radiator/condenser fan likely runs awhile then stops. Normal operation or nearing end of life for fan/bearings?
Why doesn't engine temp "appear" to be a problem? Because the 5.0L temp monitoring scale is not linear.
If the AC works when air is forced over the condenser but doesn't work when sitting still, it's the fan, failed or failing.

The valve in the compressor, as I recall, was a defective assembly from the manufacturer. Unlikely problem after ten years.

A drop of PAG refrigerant oil in the access port demonstrates good Schraeder valves. Replacing perfectly good valves is profitable for the shop if not part of necessary evacuating and recharging the system. The tool for under pressure valve core replacement typically requires more clearance than available.

Evacuating and recharging the system may be appropriate for certain repairs or when a problem cannot otherwise be diagnosed. (Especially true after home brew, single hose charging.) When in doubt, weighing in the charge with an electronic scale does provide a known basis for evaluation.

Back to the original problem: the simplest answer is most likely. Since the refrigerant charge has been checked, it's the fan.

 

Do this first.

Completely normal to have refrigerant loss over 10 years. BMW, for example, identifies long-term loss as normal operation. I haven't found Jag's equivalent TSB, but refrigerant declines on all cars over 10 years.

The right way to do it is to use a recharge machine. "Topoff" without full recharge is not*. Pressure gauges are not an accurate measure of refrigerant levels. The machine pumps out all the refrigerant, including the oil, and stores the R134 in a tank. Oil is separated and measured. Refrigerant replacement is measured by weight, not pressure. Oil replacement is measured by volume. Both amounts are specific to specific models.

Usually the machine will indicate that it's down some percentage (my BMW E60 was down 50% after 10 years usage). The tech will then use the machine to pump in the correct weight, plus inject new system oil. Denso recommends certain of it's oil for certain compressor types. Some services recommend the drier be replaced.

Usual cost should be about $100-120 for a measured recharge. Whole job takes an hour or so.

This is one thing you can't do at home. Remember, for this job gauges and auto store cans are the wrong way to do it.

Why this first? It's cheap compared to chasing a compressor and other "maybe it's broken" system parts.

My DIY garage has a machine, and charges $75. I plan to do my '07 XK this summer.

(* Can't think of accurately measuring weight in the system without removing all refrigerant and replacing from zero with the correct amount. So how can "topping it off" be accurate?)

 

Opinions vary: A competent technician, familiar with the system, can evaluate system performance with the evaporator fan at full speed, fixed engine RPM, and at reasonable ambient temperatures by observing system pressures and evaporator/suction superheat temperature. "Topping-off" requires less time and materials. It avoids the possibility of contamination associated with refrigerant recovery/reuse. Contamination is even more likely when using a DIY shop recovery machine. Refrigerant removal/recovery has its place, as does "topping-off".
PS: I suspect that your refrigerant recovery/recharge cost estimate is out of date for most markets.

 

There are pinpoint tests in the workshop manual.
FYI, in all these years I have never had a coolant leak… but I have replaced the fan resistor and the fan unit (at separate times).

 

Good tech: You could be entirely right. If they explained their topping off procedure, I might step up to it if it's more than "shoot in some gas and call it a day". Guess I'm skeptical of many mechanics, particularly with an unusual (to them) car.

Contamination: Good point. Age of the doc is unknown, but the problem is widespread: https://www.aa1car.com/library/us397.htm I'm checking into whether machines have contamination detectors. There are refrigerant identifiers to confirm source. Some detect air contamination. https://www.epa.gov/mvac/handling-co...20refrigerants.

Price: Good point. Autozone estimates $150-300, but I assume it's as much as the shop can get away with.

Thanks

 

The Direct Pressure Sensing Valve appears to act as a pressure actuated unloader. Documented failure appears to allow refrigerant bypass from high to low reducing compressor capacity. A "stuck" (open) valve will present same as leaky compressor reed valves: High pressure too low, low pressure too high with minimum refrigeration effect. (large pipe not cold immediately after start-up.) With a failing radiator/condenser fan, the large pipe will be cold, at least initially, shortly after start-up. Note: extreme temperatures may affect those guides.

The service bulletin describes a wear item but I understood it to be a manufacturing defect. However, it could be a wear item after ten years, so thanks for posting. Proper diagnosis could save a compressor for the cost of the DPS valve.

I couldn't access the Service Bulletin so, found at NTSB website: