It’s been hot here in the DC area. Hot and humid. Over 90F (or 32C for the friends overseas) and I can’t get the air coming out of the vents to come out any colder than 70F (21C). Is that what this system can top out at?
The system seems charged. At idle, the low side is about 40psi. The compressor seems to run, but the high side stays at about 170psi. It never seems to click off, the clutch is spinning, and I believe it’s trying to cool…but it never gets cold.
When I get on the gas (in Park) the low side drops, but not the high side. That seems to stay constant…more or less.
I had this system vacuumed and recharged by a shop maybe two years ago? Frankly, the AC has never been great over the years I’ve owned it.
This morning, it’s 80F outside and the air coming out got down to 47F. So the system is working.
Most cars I’ve owned struggle when the ambient temp is very hot outside, especially humid too. I’ve found generally, the AC can only cool down the outside air temp by 20-25F. And that’s only if I turn on REC for recirculating air. Not sure how to do that on an XJS.
Maybe the heater valve is stuck on. Pinch off the heater hose. Any other close like blend flap problems or bad/clogged expansion valve is harder to diagnose
Your right Veekay, it has been terrible hot around here! My 94 4.0 coupe while having issues with the drivers blower, is blowing cold air and the passenger fan is maintaining set temp. I’m not sure what the cool air temp is since I have not measured it but the car is very comfortable.
Hi Veekay. Don’t know if this is helpful, but my 95 XJS had the dryer replaced two years ago and the AC ha blown ice cold ever since (even on the hottest and most humid of days).
Think the part cost about $40.
Good luck with it!
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
8
Replacing the dryer involves discharging and recharging the refrigerant. While dryers do get obstructed, it’s more likely your excellent performance is the result of proper charging.
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Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
9
I dunno that much about the AJ16 engine compartment, but that clearly indicates a malfunction. In general terms, three malfunctions could cause such symptoms: 1) The refrigeration cycle is not operating properly, possibly because it’s low on refrigerant. 2) The refrigeration cycle is working fine but the heater is engaged and fighting against it; or 3) Both the refrigeration and heating systems are working fine but the control system thinks the car is comfortable right now.
We’ll probably need more data to ascertain which is which. First off, there should be a suction line that goes from the evaporator connection on the firewall to the compressor. When running, that pipe should be cold, cold enough there’s condensation on it. Is that the case?
I will be away from the car for a little while, so won’t be able to test anything…
I appreciate the help and will certainly pick this up where I dropped off today.
Ambient temps this morning was 80F from my thermometer in the car. That same thermometer registered almost 42F air coming out of the vents this morning. I couldn’t get it under 70F yesterday afternoon, and that was with a solid 20 minute highway drive, then a 10 minute local road drive.
I suspect that it may be cold air fighting warm air. The AC has been set to manual for awhile now, to remove the car’s interior cabin temp sensor. I don’t want to introduce that possibility.
The car’s drier has been replaced at least twice over the last few years.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
11
Just replacing the drier is no guarantee, as a frightening percentage of A/C techs routinely undercharge systems as a matter of course. The symptoms of an undercharged system are typically that they seem to cool just fine when it’s cool out, but when it gets really hot they can’t keep up.
OTOH, the symptoms of the heating fighting the cooling would be that the system works just great when the car is first started and the engine is cold, but gets worse and worse as the engine warms up.
I agree with a previous poster that simply pinching or otherwise blocking the coolant to the heater core would be a good thing to try. It’ll either make a dramatic difference or no difference at all!
Yes (Kirby) … The AC recharge was done when the drier was replaced. ~ The facelift AC controls allow you to mix “heat” with the AC flow for a “temp-control” in the cabin.
In the morning, when i drive to work, the AC gets down to 40F! Mind you, it’s 80F outside at this point. Sometimes super humid, sometimes not as much.
When I take the car home, sometimes it takes a while to get down to 50F. Like it’s struggling to catch up. It’ll blow 70F rather quickly, but then takes a long time to get down to 60F. It will eventually get there, and then into the 50s, but not like when I start it up in the morning.
Is there anything that can make the AC work like that?
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
15
Yes. It’ll behave like that when it is undercharged.
It doesn’t seem to want to take any more r134a. Maybe that was before I kinda fixed the heater control valve. I think it was stuck. I might want to try again I suppose?
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
17
