It was -11C the other day and I took my car on a 12 mile drive to work and the first thing was the drivers heated seat had stopped working and the leather seats were very cold, also the heater didn’t blow out hot air just luke warm even though the engine was up to normal temp.
Is there a calibration procedure for Jag climate control, in my Saabs I just press a sequence of buttons and the actuators and air doors cycle through their full range of positions. Does Jaguar have anything like this as I suspect tje airblend door isn’t going to full hot.
My passenger heated seat works and the red and yellow lights work for the drivers seat but no heat, I have to get under the seat and check if there is output from the seat module, I tested the heater matrix with an ohm meter and that was ok. One thing is the last time I used the seat it was getting way too hot even on half heat as if the thermostat wasn’t working, I had to turn it off after 30-40 seconds!
could it be the stat has failed completely and telling the module to turn the seat heater off, any info or advice much appreciated. I have fixed many seats on Volvos which were a simple circuit with no module in the system, but the Jag set up is new to me.

 

Norcat,lets deal with one issue at a time and we can get you comfy in your kitty once again.

As for the seats, odds are, what you was experiencing was a very hot spot, not so much the whole seat getting too hot (this is normally the case). What happens is as you sit on the seat, you bend the heating element back and forth. Like what happens with a coat hanger when you bend it back and forth, the metal gets weak and then breaks. In this case, as the metal is breaking, it creates a higher resistance area which causes the seat to get much hotter in a single spot than normal. But, when that spot finally breaks, it opens the circuit to the heater and it makes no heat. To fix this, what you are going to have to do is remove the leather off of the seat. This will expose a white cover. If you look at this white cover, you will see dark spots. Those are your spots that were getting too hot. These are also your spots that you are most likely to find your opens in the circuit (just because you find one, does not mean that there are not others!!!!!!!). What you are going to want to do is rip the white cover a little bit to expose the metal banding inside. Using a multimeter, measure from good metal through the burned area, to good metal on the other side. You should see a few ohms of resistance. If you are seeing over 5 ohms/inch (2 ohms per CM), the metal needs to be repaired to restore the circuit. The easiest way is to get a piece of copper wire that is 18 AWG, solid (no stranded wire). What you are going to do is cut a length of wire that extends about 1/2" (1 cm) beyond the burn area on each side. You are then going to use a soldering iron to solder the full length of the wire. Do this for every hot spot you find. Then you can put the leather back on after testing the seat to make sure you have even heating across the seat.

Now, for your dash heat. This can be caused by a few things: 1) clogged heater core, 2) climate actuators that are not going to the full position, and 3) failing water pump. If your water pump is more than about 4-5 years old, I would suspect that first. Next check you can do is to attempt to use your front defrost. Can you get hot air out of that, but not out of the dash vents? If so, it could be a blend door issue. If you suspect a blend door issue, you will need to remove your glove box and look at the end of the rods that do your heating and cooling (there wil be three rods, one coming all the way through each of the actuators). If you put the climate control into manual mode, you should be able to cause each of these to move through about a 90 degree range of motion. If in doubt, you can remove the actuator and move the flappers by hand. If you can move them further by hand then the actuator is, you have a bad actuator.. Just make sure not to change the settings on the actuators when you have them disconnected. If all this has proven to not show the problem, I would then recommend that you drain some coolant and try blowing some air through your heater core. It should blow with minimal restriction. if it is building up pressure, you have a blocked heater core. if this is your case, let me know and I can possibly help you clear the obstruction.

 

Many thanks Thermo for your detailed reply, I will take the car into work next week and investigate further, any tips on removing the leather before I start.
Also if the water pump was failing I would have thought the engine would run hotter due to poorer circulation?

 

Norcat, I would focus on the seat first (not the back) as this will be easier to wrok on. To remove the leather, should be nothing more than a series of metal rings on the under side of the seat that you need to loosen. From there, the leather should just peel off with minimal effort. The big thing will be getting one side tied down so you can then start pulling the leather around and get it properly pulled so you do not end up with gaps in the bottom of the seat.

As for why the car is not overheating, you have more cooling coming from the radiator because the temp difference between the outside air and the coolant is larger and you are getting more losses from the block of the engine as compared to say the middle of the summer. These 2 things can help overcome a slowly lowering amount of flow from occurring.

 

Btw.: To remove the leather I'd say you have to remove the seat from the car first. This includes pulling off the connector coming in from the front. A small bolt needs to be loosed first to pull the connector off. Before doing so, you might want to either disconnect the battery, or at the very least pull the fuse for the airbag in the seat. Better save than sorry.

In case you were wondering, why you measure continuity on your heater matrix, if - as Thermo wrote - the matrix might be broken on 1 or more points (which makes sense): It is quite possible that there is an intermittent contact. The contact is there, when you measure for continuity, but the contact is gone, once you sit in your car (the weight of driver would break the momentary connection).