When I turn on my 3.0 engine everything seems fine except when I turn on my air conditioner, my jag quits running. I was thinking it is probably the compressor, but why would the compressor cause my engine to stall? Perhaps the compressor is frozen and when the compressor clutch engages, it stops because there's too much strain on the engine? Why do I not hear screeching of the belt if this is happening? No one on the internet seems to have this problem. Can anyone help me. please?

 

Giswme, I am thinking the same thing you are. The A/C compressor is frozen. I had a friend that his compressor froze up and because he had his A/C turned on, it would not allow him to start his truck. So, I can see where this can be a situation for you. Should there be alteast a chirp, I would think so. But, eveyrthing seems to be pointing to what you are thinking.

 

Thermo,
Thanks for the tip, but this morning I had my wife start the car without starting the a/c, which is having the settings low on a/c, without turning on the main knob button. I signaled for her to start the a/c and then the engine stopped as soon as the compressor clutch engaged. Then I told her to turn engine off ensuring the air con was off and then restart it, just to make sure it was the compressor, but this time the jag didn't stall and the compressor was engaged. It stayed running and blowing out super cold air because it was set at the lowest setting. Could this be an overcharging of the a/c system? I did notice that only one of the fans was working hard while the a/c was at its lowest setting although it hadn't gotten hot enough for both to turn on. I thought perhaps there could be an electrical problem?
A week ago I was riding in the jag and it was a hot day. I had turned the ac on and was accelerating a bit to about 45 mph when the engine went into what seemed like limp mode but it felt more like a transmission shift to 3 and then 2 and then it died. I turned off the a/c and put it in neutral and started it while going down the road and it ran like a champ without the a/c. I am very perplexed.I am going to check the high and low pressure a/c system next. I'll let you know what I find.

 

Giswme, if the system is over charged, yes, you could possibly see this. Granted, I would think it would need to be grossly overcharged. If this seems to be your likely suspect, you may want to spend say the $80 at a local Midas shop to have them pump out the freon that is currently in the car and have them do a proper fill (which is done by measuring by weight the freon that is added). Until the system gets a true vacuum pulled on it and then filled, any fill done will be a guess. Yes, pressures will get you close and normally are good enough. But, if you want to be sure, weight is the way to go.

Because you are guessing that the freon system may be overly charged, I take it you recently added some freon due to the A/C not working well while driving in town. If you set the temp to the lowest value that it will go and set the fan to the maximum speed, both fans should kick on and blow at maximum speed. If you are only getting 1 fan to run, then you also have a problem with your fan controller. Then most likely the fan that is not turning lead to the A/C not working like you thought it should.

 

Thank you kindly, Sir, I really do appreciate your quick replies, Thermo, and for your words of wisdom and experience.
I had expended all of the freon from the system around two years ago because I had replaced the compressor with a re-manufactured one. I had the same problem back then with the car stalling after turning on a/c. I had decompressed the system before filling the a/c system to the weight amount on the Jag label stated. It ran good for a while and now lately it's been doing the same thing. Right now, as I attached the pressure hoses to the car while it was off, it read 80 psi on low and 80 psi on high. This seemed a little high but at least it was equalized. Then I turned engine on and turned a/c on. The car did not stall. I let it run for 10 min while watching the compressor run engaged. The clutch never disengaged, the compressor kept on turning. Cold air was still blowing inside, however, the low fluctuated a bit from 30 to 40 and the high went from 135 to 210. The temperature outside was close to 90 degrees and low humidity. the secondary fan never turned on even after idling for more than 10 min with the A/C on. Now after 10 minutes, high side went to 310 psi and low side to 46 psi. The air inside the cabin had lost some coolness. I turned off a/c after 15 min and it read 85 low and 100 high. I then turned the a/c back on and it read 40 low and 290 high.I reluctantly turned off the car and it gradually went down to 82 low and 90 high, which explains why at the start it read 80 psi low and 80 psi high, it wanted to equalize but very high.
My other dilemma now is with the fan not turning. You mentioned the fan controller, which it a very good lead, but how can I be sure it is the fan controller and not a fuse or bad fan? I will check the fuse and the connectors and try to sort this out.
Thank you, Thermo, you spur me on to overcome this problem and yes, I will bring it to a shop if all else fails.

 

Giswme, I can rule out a fuse because there is only 1 fuse that powers both fans. So, if one is spinning, then the other should be too. I would also venture to guess that the fan that is spinning is not spinning as fast as it should be. If you turn on the A/C and the fan starts blowing, you should be getting a pretty good volume of air (ie, enough that it should be blowing your air around some). If you are getting a nice gentle breeze, the fan is not spinning like it should. The other check you can do is to connect a multimeter across the terminals of the fan that is not turning. With the A/C on max, you should be seeing 12-13 VDC. If you are seeing 1-2 or nothing at all, controller is bad. Honestly, anything under 10 VDC I would consider bad if the fans are being told to run at full speed.

Now, for the pressures that you are seeing. Those are fairly normal for the temp. The freon will build up a higher pressure the hotter it gets. At around 90F, the freon will naturally be at around 90 psig. So, what you are seeing is normal and expected. With the motor running, there are piping losses and the compression of the freon, that is where your pressure variations come in. so, seeing the pressures that you are all fall within normal operating ranges. There is a switch that will turn off the A/C compressor at like 560 psig (prevents damage to the compressor at high engine RPMs).

Now, I have to ask a question because I can potentially see a problem here that is going to help narrow things down and explain the poor A/C operation. When you replaced the compressor, did you have a vacuum drawn on the system before adding the freon? YOU MUST DO THIS!!!!! This is done for 2 reasons. The first being that having standard air in the freon system makes the freon not respond properly and in general, will make the A/C not run efficiently. The second being that having air in the system also introduced water into the system (any humidity in the air). This can have negative effects on the piping in the ways of corrosion and potentially damage to the freon (freon does not remain freon when subjected to water and then exposed to heat). Once you start getting something other than just freon and its associated oil in the system, what happens is hard to say.