So, as some of you may remember, I had this issue a few months ago after I changed my DCCV. The AC would only blow humid warm air, sometimes, then other it would work fine. I thought it could be a sticky DCCV, since it seemed that cycling the temp from HI to LO a few times made it start working. However, this doesn't seem to have solved it as it started acting up again a couple weeks ago. The mystery is that for days, or weeks, at a time when you start the car up there is nice cold air right away, or at least within a few minutes. Then, for days in a row there is nothing but warm humid air for various periods of time (sometimes 10min sometimes an hour) and cycling HI/LO does nothing. As well, sometimes it will start out nice and cold, then decide after a while to become warm and humid, then back to cold and so on. I did notice (could be a coincidence) that when it is blowing warm that if you use the J-gate and drop it to 3 or so and bring the rpm up to say 4000 for a min or two, it starts blowing cold again either right after or soon after this. Now since my wife drives the car now, I have only been able to try this rev thing two or three times so I don't know if it means anything. Since it's really hot here, this has become quite annoying for my wife! So, since I know that the car is capable of producing ice cold AC that the system works. But what is the problem? My thought is the temp sensors (one in dash and those three others). I also know there is some kind of pressure sensor in the AC system that will shut the compressor off if it things the refrigerant is low to prevent damage (or something to that effect). Could that be bad? Could there still after all this time be a lingering air bubble in the system? Could the compressor be on its way out. Maybe the compressor clutch is sticking or slipping or something and causing this. Lastly, the only thing I can think of is maybe the accessory belt is slipping. It is old and should be replaced (i have a new one ready to go in). Anyway, since I have to place an order soon for a bunch of parts for my knock sensor replacement involving the taking the blower off, I figured I would add the temp sensors to the list (cheap and can't hurt replacing after all this time) and maybe that AC pressure sensor (or whatever it is) if it's necessary. So, to all you wonderful people out there who know much more than I, what do you think?
Thanks

ps. I will be taking a good look at everything (ie. AC compressor) when I have the engine torn down with the blower off and replacing the accessory and blower belts.

Forgot to add, could it be my RCCM? I know they are pretty tough but who knows if it got damaged. I do have a spare one sitting around, worth swapping it in to see what happens?

Just realized the first thing I should probably do is get the AC system checked to see if maybe the system just needs a recharge! I'll do that as soon as I can.

 

With so many possible sensors I'd want to be able to read them when the system's working then again when not working to see what's working and what isn't.

AE can do it and can also say whether the A/C is commanded on, as well as the HiLo pressure switch. Much cheaper but a lot of hassle to DIY without such a tool.

 

While it would be easer with AE, my reasoning is this: These sensors are really not that expensive. This car is almost 10 years old with 125000mi. Things are getting old so replacing them couldn't hurt.
But, first of all I am going to check the system pressure. Maybe it's just low. I mean as far as I know this system has never been checked or charged in 10 years. Could be as simple as a recharge, I hope!

 

I don't see how it can sometimes work and not others if it's the A/C charge.

 

Have you checked out the threads regarding switching out the compressor valve spring in the back of the compressor - not sure if this fix applies to the STR V8 compressor but the symptoms you describe sounds similar.

Here you go compliments of joycesjag:

https://www.jaguarforums.com/forum/a...b00183nas1-pdf

Good Luck!

 

I don't think it's the charge either, since it will work then stop then work again, but I think I'll still check it. To me it seems more light a faulty sensor that would cause it to start and stop like that. My first guess would be the ac pressure sensor since it can turn off the compressor when it thinks the pressure is low. That would explain it starting fine sometimes, then stopping, then starting again if it's sending faulty signals at random intervals. Thanks for the tip abonano but I think that only applies to the 3.0, and I don't want to mess with my compressor if I don't have to, as far as I know it's burried deep in there somewhere and I don't want to have to find it! I am reluctant to think the in cabin sensors in the footwells since I believe those can cause differences in temp between sides and I don't have that problem, but I will check them anyway. Possibly the in dash one if that controls the entire system, but it's cheap as well so I will probably just replace it. So, for the AC pressure sensor I get part XR83792. I read on here in another thread that the sensors in the footwells and dash are the same as the motorcraft ones (YH1504 footwell and YH1505 in dash). Anyone back me up on these numbers?
Thanks

 

I've just done a sat nav retrofit.

I had the exact same problem. It turned out to be the rccm.

It had a burnt track on the circuit board which I had repaired with a simple wire bridge over the break. Now it's blowing ice cold once again.

I bought the rccm, but I think it was not working when I had it, as my original CCM when reinstalled worked the AC perfectly fine.

If you have a spare rccm, switch it out, I'll almost bet you that this is th problem.

If you had a faulty DCCV previously, then this would have blown the track on the RCCM as it would be sending too much current to the Rccm and hence blow a track on the circuit board.

Try the alternative rccm, really easy to swap over behind the glove box. If that works, check out the damage within the RCCM, you may well see the burnt track.

Hope this helps,

Tris.

 

With a blown track it's hard to see how you'd get the problems reported.

 

I can only comment on what I have experienced with mine JagV8.

My RCCM had a blown track. I had aircon blowing warm air. I repaired the blown track, aircon blew cold air again after the track was repaired..........

At the end of the day, what has he got to lose by switching out the RCCM with the spare one he has???

 

Yes but his sometimes is hot and sometimes cold. A blown track cannot do both.

The RCCM is still a suspect, but not for a blown track.

 

I see what you mean.

With mine, I was getting warm air from all vents, but cold from one.

 

Thanks for the info, but as JagV8 said the normal symptoms of a bad ccm is different temps from different vents. I've been through the whole DCCV and CCM thing many times (just put in the fourth DCCV when I did it last time and on my second CCM), this doesn't seem like a bad RCCM, but again, who knows! I just priced out the AC pressure sensor and can get it for $31, and the in dash one and the other three for about $15 a piece from rockauto so I think I'll give those a try. If all else fails I can swap the RCCM with my spare one. Again, since sometimes you start the car up and ice cold air comes out in like a min and works for the whole trip, or stops after a while, then starts again, or takes like 15min to get cold air. All vents are the same temp, and since it does get ice cold everything does work, just not all the time! I keep coming back to the idea that the AC pressure sensor controls turning the compressor off and on if it thinks the high side pressure is too high. If it was really too high, why did all of a sudden this happen after years of working perfect. If that sensor is faulty it could turn the compressor off and on at will, causing my exact problem. That will be my first thing to check and replace.

 

If I had to guess (I'd rather read sensors etc LOL) I'd go for a chafed wire or bad connector.

hmm, bad KS as well.... does it share any wiring at all with anything in the A/C control system? (Needs concentration on the elec guide)

 

Members with the 4.2/4.2STR have swapped the compressor valve spring with success. I know it's a royal PIA to get to but was a suggestion nonetheless based on the symptoms you were describing. If the AC sensors don't alleviate the symptoms then you should focus on the compressor.

 

The AC started acting up well before the KS started going bad, by about two months since it really started shortly after I changed the DCCV, so I don't think they are related, but you never know! I hate chasing wires so I'll leave that one til the end if nothing else fixes it! Same with the compressor valve spring, it may be the problem (or the compressor itself) but as you said, it's a pig to get to so I'll start with the cheap sensors, then worry about getting at that compressor! By the time I get done with these jobs, everything from belts to seals to sensors to thermostate will be replaced and I will take a good look at the compressor. If it's still acting up, I guess its time to take a look at the wiring and compressor. Hope it doesn't come to that!

 

What are the high and low side pressures?

I had a failing compressor and tried the v6 valve/spring swap TSB on my V8. The clutch stopped engaging after the swap. It wasn't very hard to do the swap, you will just have to unbolt and bend some lines a bit.

 

Well, been a while, but update time. I just finished all my blower removal stuff, and also have now replaced all three in car temp sensors, cleaned the in dash one so its spotless (the one from rockauto IS NOT the correct one (Motorcraft Y1505 or Y1504) but the other three are correct), changed AC pressure cutoff switch and took a good look at the compressor while everything was off. While it has only been a day, I still seem to have the same problem. Now, the compressor looked find, no obvious leaks or anything like that. So, I am going to get the high and low pressure checked today (or as soon as I can get it done) and go from there. Maybe it just needs a recharge. After that if it still doesn't work I will swap my RCCM for the other one I have and see what happens. Finally, if all else fails, I guess I will change the in dash sensor with the correct one from Jag. At least I have narrowed down some of the possible causes!

 

I think you mean a burnt copper trace. If it's the ground trace you might be lucky by soldering a solid piece of insulated wire to replace it. If you not lucky then somethings else on the board blew as well

 

Well, got the system checked and guess what, it was low, very low. So, had them charge it back up and all seems well! I know, I know, this is one of the first things I should have checked, but since I was digging into the engine bay and the age of the car, why not refresh and replace things! Anyway, turns out a charge was all it needed.

 

Well, turns out that while the system was low and needed a recharger, that wasn't the only problem. Yesterday evening and this morning the AC started acting up again. So, I though now what, but decided to check the relay. Turns out the SC compressor clutch relay was bad. I switched it with the drivers HID headlight and guess what happened, the AC worked instantly and the headlight was out! So, looks like I found my problem. Good thing my system did need a recharge cause I would have hated to waste that money!