Dear all,

I've an issue with my AC (Type v8 4.2, 2002.5). After some minutes / hours driving (it may vary over the time), the AC does not blow air anymore whichever the air vent is selected. I must stop the car several minutes to get it work again.

This is really annoying the night by cold weather because I cannot defrost the windshield and I have to stop the car.

When this happens, I can heard the air flow motor running, I can change the air flow speed but no air on the air vent. I tried the following during driving:
- switch on / switch off the AC => still the issue ;
- when the AC is switch off, try to get "natural airflow" through the air vent => still the issue. I opened the sunroof to create a depression => sometimes it works and I got normal air flow;
- I tried to change the air vent (windshield, feet, face, ...) => still the issue;
- I tried to enable / disable the recirculation => still the issue.

Everything behaves like if something blocks the air pipe from outside.

Any idea ?

Thanks,

Laurent

Edit: added car model.

 

Hmm, hard to say what is happening. Good troubleshooting so far.

Maybe try inspecting the cabin air filter, and the duct where it fits. Perhaps a plastic bag got sucked into there and is caught against the filter, blocking airflow. You might need a small mirror to inspect the duct for blockage. You could also run the fan momentarily without the filter and see if there is any difference.

Has the car been parked a long time recently? Maybe an animal built a nest in the inlet duct at the filter. This happened to a good friend. Unfortunately, the squirrel died and stunk up the whole car.

One problem with the filter clog theory. I would expect airflow to be normal when recirc mode is selected, and air doesn't flow through the filter. Still worth checking the filter and duct, though.

 

Thank you Karl for you reply.

I check at the cabin filter but there is nothing.

There are 5 actuators on the air circuit. Is there an actuator which permit to isolate the cabin from outside ? Maybe the problem can come from it. I did not see any documentation explaining the role of each one and the overall air circuit. Do you have such a document ?

Thanks you,

Laurent

 

I have this document


So for instance, I guess the defrost actuator permits to let the air flow to the windshield. But flowing from where ? Is there an kind of global inlet ? And on this inlet, is there an actuator on the path which can cut off the whole air flow ?

Laurent

 

Here's the training guide for post-facelift models. Unfortunately, it doesn't have a diagram showing airflow through the climate control system. See pages 105-118:

http://www.jagrepair.com/images/Elec...E%20Update.pdf


I just had another thought. I wonder if your AC evaporator could be icing over. All airflow goes through the evaporator, regardless if AC is selected. If it iced over, that would block all airflow no matter which mode was selected, and might take quite a while to thaw. A quick way to test: Let the car sit several hours, preferably overnight. Is your weather above freezing? You want to make sure any ice has had enough time to melt. Start the car, and immediately switch off the AC. You had previously mentioned switching off the AC, but if this was after ice had already accumulated, airflow would remain blocked for some time. If the airflow now seems normal, ice on the evaporator would be the likely culprit.

To further test, after the airflow had been blocked, park somewhere dry and cool. After an hour or two, look to see how much water collects on the ground underneath. Ideally you can park in a garage or some shady spot. You don't want to park on hot pavement, as any water dripping out will quickly evaporate. A little bit of water is normal, maybe a puddle 4 inches or so. Much bigger than that would indicate too much ice was present.

Fixing the problem is easy. Make sure the AC system is fully charged. Low refrigerant can lead to evaporator icing. If the refrigerant level is good, the evaporator temperature sensor is probably bad. The sensor feeds info to the controller to keep the evaporator slightly above freezing, for maximum cooling without ice accumulation. In that training guide, this sensor can be seen on page 118, item #7. It's the same part number as the left and right discharge sensors, items #4 and #6.

 

Air enters the plenum from one of two sources, fresh or recirc. Fresh air comes from outside through the inlet filter. Recirc air is drawn from inside the cabin (not 100% sure, but believe it bypasses the filter). The fresh/recirc door allows air from one source or the other, but can't shut off the flow. It can only select the inlet source. If this actuator failed and the door was stuck in one position, you'd still have airflow. The only variable is the source.

For air leaving the plenum, it can go to three possible outlets: The floor, dash face, or defrost. These doors are on/off, and normally at least one is always open. Sometimes, more than one door is partially open, to split airflow to different locations. If all three doors were to fail closed, this could block off all airflow.*

When the system is working normally, are you able to manually select airflow to the floor, dash face, or defrost? If so, it's hard to imagine all of these actuators simultaneously acting up and choking off the airflow leaving the plenum. (Remember, the fresh/recirc door only selects the inlet source, but can't stop airflow.) That's why I'm leaning towards my theory about ice on the evaporator. That could choke off all airflow as you've described, and would "correct" itself after parking for a little bit.



*Don't quote me on this, but I think the defrost duct is designed to always let a little bit of air clear the windshield for safety. Even when this defrost door is fully closed, the passage is not completely blocked off. So if my theory is correct, even if somehow all three outlet doors were fully closed, a door problem could not completely stop airflow to the defrost.

 

Tough problem.
Here are some of my thoughts.
After you switch the ignition off, listed to hear if the actuators are moving back the flaps to their parked position. If you're in a quiet enough area you will hear this happening. If you hear the sound, of course this means that the flaps are operational and they're at least moving. For all flaps/actuators to fail? Possible, check fuses, relays??
You say you hear the motor operating so likely that's not the issue. Ruling out flaps and motor leaves little else other than an internal blockage. A blockage in the engine bay's cabin filter area would still allow airflow within the cockpit.
Remove all plastic panels and check under the footwell area with the fan operating. Mine had a plastic bag blockage there as I was missing the footwell filter. That footwell filter should be present and clean. It acts as not only an air filter, it's there to keep the system clean.

Thin plastic bag sucked in system. Photo looking up from the passengers footwell and footwell/AC filter missing. RHD vehicle.

 

wow now that is a hell of a find. At least it was not an old stinky bag i hope

 

Thanks for the info. on the footwell filter, I had no idea there was a filter in that area. I do not think I ever remember hearing it mentioned on the Forum. I will check mine sometime, is it some kind of foam?

 

It's actually a large plastic panel that nicely clips in and covers the void below the dash very well. Has large air holes and holds the filter material.
I don't think the filter material is of a foam base. It's flimsy that's for sure and I think it may be heat melted in; the good news is it's definitely renewable though with a more durable material.
Finding one in RHD was not that easy.. Sprayed the filter with my wife's clothes prewash and hosed it off. Came up very clean!

Been a few posts over the years. jagclimatecontrol.com had a few nice photos of the LHD version filter. I suspect that site has shut down. Found one of their photos but not the best one. Doesn't show the filter very well. You can see some of the filter material. Filter shown clipped in above the word "unit".

 

Hi all,

thanks for tour answers.

I will check for the footwell filter. By the meantime, to answer some questions:
- yes, I can heard the actuators moving back to their parked position;
- this is confirmed by the data stream on the AC calculator (the value of the different flaps are changing depending on the air vent selected);
- I can read a "evaporator air-off temperature" of 26C (with the AC switched on). I think this a little bit high.

What do you think of this temperature ?

Thank you,

Laurent

 

I know these are basic questions; have you checked there's enough refrigerant and oil in the system? Checked the system's keeping pressure? Checked the compressor and the whole system for leaks?
Mine would turn on and off haphazardly. I immediately thought it would be every other problem except lack of refrigerant and oil in the system.. Turns out it was just that.

 

Is this the value reported by the sensor measuring temperature at the evaporator? If so, that is very high with the AC running.

If we are talking about the correct sensor, this one is very important. It monitors the evaporator temperature and controls the compressor to keep things just above the point of freezing. If the sensor is erroneously sending a high value, the compressor is never told to shut off and ice will accumulate, eventually shutting off airflow.

Have you tried a test drive with the AC switched off, as suggested in post #5? I think you will find the airflow is fine as long as the AC is switched off, with no way for ice to accumulate.

 

A couple more thoughts. Try the test drive with the AC switch off, as previously suggested. If the airflow is normal with the AC off, but drops off soon after turning the AC on again, here are two more things you can do:

1) Put a pocket thermometer in the center vent:




Turn the AC on and toggle the temperature selector down until LO is displayed. Go for a test drive and watch the thermometer. The thermometer should not get any lower than approximately 38F (3.3C). I bet you will find the temperature initially getting lower than that, and allowing ice to accumulate on the evaporator. Once ice builds up and blocks airflow, the temperature will increase.

2) If the temperature gets below 38F, the evaporator discharge temperature sensor is the most likely culprit. You can check the sensor as detailed in post #3 here:

https://www.jaguarforums.com/forum/s...2/#post1714571

You can remove the sensor and compare it to the chart. For giggles, this sensor is the same part number as the left and right duct discharge sensors. Let the car sit for several hours so all sensors are the same temperature and then compare them. Instead of removing the sensors, you can read them from the connector at the back of the control module, which is generally easier than standing on your head to access the sensors directly. See figure 06.1 in the wiring diagram for the three sensors across the top of the page:

http://www.jagrepair.com/images/Auto...42002.50en.pdf

 

Hello all,

thanks for all these advices. I will drive 500 miles next week, I will try to drive without AC to see what happens.

Otherwise, the AC has been refilled some weeks ago and the problem was already there. We did not notice any leaks.

Finally, to read the sensors values, I'm using the OBD2 values. Is-it better to read it directly on the connector ?

Thanks,

Laurent

 

Not really. Reading the resistance value for this sensor? It would just be confirmation that the sensor is bad, instead of relying entirely on the OBD2 data. This is merely two methods to arrive at the same conclusion of a bad sensor.

 

Just check the temperatures after 4-5 hours. The names on the OBD2 are the following ones:
- Evaporator air-off temperature: 38C;
- Interior temperature: 26C;
- Air conditioning passenger's heater sensor: 25C.

These are the only temperatures I can read with OBD2. The evaporator temperature is not coherent with the other ones.

I started the AC and the temperatures "interiors" and "passengers" fall down to 20 whereas the evaporator only fall down to 32...

I will check again tomorrow morning when the engine will be totally cold. Depending on the results, I will try to swap the driver and evaporator one to check is the temperatures are swapped as well or not.

Laurent

 

Hi all,

I checked this morning with the engine totally cold. I found out the temperature for the driver air temp. The values were:
- passenger: 17;
- driver: 18;
- interior: 18;
- evaporator: 34.

I swapped the driver and evaporator sensor and now the evaporator has a relevant temperature. After switching on the AC for 5 minutes, the temperatures were:
- driver: 30;
- passenger: 6;
- evaporator: 4.

So I think I had a serious evaporator icing issue.

I will check this week-end if it solves the overall issue.

Thanks a lot Karl and others for your help, I let you know next week if everything is OK !

Laurent

 

Fingers crossed, but it sounds like you found the problem. The AC system should hopefully work okay now in manual mode. You may find yourself getting very cold, and have to switch the AC on and off to stay comfortable.

The sensor is a very common Ford part, used on many vehicles from that era. I installed a Motorcraft YH1504 on my '02, and think that same number is good for all years.

 

Hi all,

so I drove 500 miles today with AC on. No problem !

Thanks all for you advices and especially Karl, you identified the issue and permit me to solve it ! :-)

Laurent