Hey fellas I got an 02 S type 4.0 running like a champ but the ac. I'm testng the engine fan after replacement of compressor, condensor, acumilator, hoses, not the expansion valve yet, because I can't get the ac cold sitting at idle cause engine cooling fan won't turn on with controls set to Low AC recycle air. Air is just not cold and dry.
I checked the temp sensor and fan for high speed simply by unplugging the fan until the temperature reads 220 on my OBDII reader and plugging it back in and fan spinning high and reduces to low at about 205. I can see fan turn on low at about 170.
I swapped fan control module before testing temp
sensor so now I'd like to create the high pressure switch working electronically.
Can I cross the leads in the harnes with a paper clip?
When i unplug high press switch the compressor doesn't run at all so at least 1 of the 3 pins energizes the compressor.
I'm told here that 2 sensors control fan. Ac switch and temp sensor. AC commands high speed only and temp is 2 speeds high and low.
thanks for the help

Pointing to brown wire thinking it's ground. No voltage reading when grounded to chasis

 

Not quite. Wiring diagrams here, see fig 3.2 for the AC Pressure Switch, near the bottom of the page:

http://www.jagrepair.com/images/Auto...x2032002en.pdf


At the plug, pin 1 is the ref voltage supply and 2 is the ground. Pin 3 is the variable output, in response to the pressure at the switch.

When you disconnected this plug, I think the controller is smart enough to realize it doesn't have valid data for the high side pressure. Because the controller now has no way to know what is happening, it crosses it arms and says, "I'm not turning on the compressor" just to be safe.

I'm not really sure how best to troubleshoot a suspect pressure switch. The only thing I can suggest is to try a new one. Sorry I don't have a better answer for you.

You said you're not getting any cooling at idle, stopped in traffic. You should be able to duplicate this parked in your driveway, right? If so, can you confirm the compressor is actually running? Maybe the fault isn't the pressure switch.

 

I'm trying to prove to some one the fan isn't the issue. The compressor definitely turns on because it's making a little racket unlike it did when it was replaced about 7 months ago.
The air isn't cold moving at highway speeds set up on max air trying to use forced air thru condensor.
I just wanted to be able to really varifi the fan and fan control module were working as they should in a bench test situation.
I unplugged a plug on the passenger side to disconnect the fan and watched temps get up to 220 and then with engine off I plugged it back in and the fan kicked on high. With engine running watched temps decrease and heard the fan reduce speed. I felt like the temp sensor was working and sent signal to the fan control module as designed.
It's my understanding there's only a high pressure switch on the ac line and the low pressure switch is part of the compressor.
Does the switch turn the compressor off when pressure is to high? If so wouldn't the fan turn off as well?
I dont have the knowledge of how to read the wire diagram.

 

Ah, this is a HUGE clue. Wish I knew this earlier. I'd suggest not worrying about the fan for the moment. The fan could be totally kaput and you'd still have adequate cooling above 30 MPH or so due to ram airflow through the condenser. Your fan and the control system may be perfectly fine. I'd only worry about the fan if cooling was good on the highway but poor at low speeds, but that is not your situation. Your cooling is poor at all speeds.

Have you seen my monument to verbosity for troubleshooting the climate control system? It's carefully organized to point you towards a proper diagnosis:

https://www.jaguarforums.com/forum/s...ol-how-185002/


Specifically, start with the test of the DCCV in post #2. If good, measure the duct temperature in manual mode (LO displayed) and compare to ambient. Use a thermometer, don't just guess. If there's some cooling, proceed to post #4. If no cooling (duct temperature same as ambient), go to post #5. Don't skip around. Please follow the steps in the order they are listed.


Please see my comments above on the fan. Fix the known issue first (inadequate cooling at any speed). After that, I bet you will find the fan is okay.


Yep, I'd say that's a good test of the interface between the engine coolant temperature sensor and the cooling fan.


​​​​​​​Sorry, only half right. In this AC system, there is only ONE pressure sensor. It's on the high side. More details in my guide, right after the last picture in post #1.

There is no pressure switch on the low side, in the compressor or anywhere else. This is very different from most vehicles. Low side pressure is inferred by measuring the evaporator discharge temperature.


​​​​​​​Yes, if the high side pressure rises above 420 PSI, the compressor is switched off.

​​​​​​​I'm not sure. Even with the compressor switched off, the fan may still be commanded on to cool off the high side and help reduce the pressure. Just a guess, though.

​​​​​​​Remember, I'd suggest not worrying about the fan details right now. Work through the troubleshooting guide and I bet you'll find the root cause for insufficient cooling.

 

 

For the moment, I wouldn't be too concerned about flushing the system unless you had found debris from a failed compressor.

Be wary of assuming the new compressor had failed. Start your troubleshooting with an open mind. Don't just make the symptoms fit your hunch, especially with expensive parts.

With a new compressor and other parts, I'm assuming (Danger! Danger!) you did a full vacuum evacuation and recharge. I had previously suggested not to skip around the troubleshooting guide, but since the refrigerant level is likely okay (unless you have a major leak), you can safely skip over that section for now. Try all of the other things in post #4 (inadequate cooling in auto and manual modes) and only come back to rechecking the refrigerant level after checking everything else. Specifically, check the relay for arcing (swap with a known good relay) and check the compressor clutch for slippage (using paint marks).

I can't remember if I included it in the guide, but make sure the relay fits snugly when installed. Get a thin strip of metal the same dimensions as the tabs on the relay. Make sure each receptacle grips tightly. A loose socket will limit current flow and reduce the clamping force of the compressor clutch.

Also see post #17 for how to diagnose an evaporator temp sensor that is letting ice build up, and #18 for a slipping drive belt (try some belt dressing).