heated seat diagnostic help needed
 

Hi, I have a 2007 LR3 HSE. Neither of the heated seats up front work. The ones in the rear do work. When I push to the buttons to turn on the front seats, the small amber lights turn on and I can adjust the setting to level 1, level 2 or off (one light, two lights, no lights). Everything seems to be working fine except neither of the seats heat up. I have checked all the fuses and found no smoking gun. I should say that I checked the fuses in the panel under the hood and in the glove compartment.

I can't imagine that both of the front seats would have failed. Can anyone point me in the right direction?

I have just found the attached wiring diagram but honestly I don't know where the where the Automatic Temperature Control Module (D243) is located. I assume that the Central Junction Box (P101) is where I found the fuses under the hood.

I took it to my local Rover mechanic and he wasn't too helpful. He just gave me a $2000 estimate to swap out everything. I would like to try it myself but I need to know where that Temperature Control Module is first.

Thanks
Matt

PS - My wife didn't appreciate the seat heaters not working last winter and there isn't a whole lot left of this summer here in Alaska.

Link to a six page heater wiring diagram
 

The link below is to a six page pdf re the power seats and seat heating, front and rear, that you can download and print out. The additional sheets may help you figure out what is going on. The problem could be as simple as a partly disconnected electrical connector under one of the front seats or a failed fuse. I would look for something simple and a failed fuse can be hard to find, let alone test.

I say that as since the rear seat heaters work, I doubt the problem is any of the fancy stuff. The solution will be something simple. The ATCM is the bit with the round knobs under the radio. It is the "computer" and for the most part, all the Land Rover circuit board things are fairly reliable -it is the simple stuff that gives the trouble.

DISCO3.CO.UK Photo Gallery - LR3 miscellaneous/Wheel cut thru definitions and specs

Also if you have not done so, try a hard reset. Sometimes the problem is that the software is mixed up and a hard reset can sometimes solve problems, in this case unlikely but the hard reset does not do any damage and can solve silly problems.

Hard Reset Instructions

In brief, to start the hard reset process, open the hood but close all doors and let your 3 go to sleep - no radio display etc and no key in the ignition. This will take a couple of minutes and do not open any doors until the reset is completed. (I find that it is often a good idea to have the drivers door window rolled down and the key in my pocket whenever fooling about the vehicle.)

Disconnect the ground battery terminal from the main starting battery.
Disconnect the positive battery terminal from the main starting battery.

(I assume that you only have one battery in your 3. If not, disconnect the others as well and leave them disconnected until after all is done.)

Connect the negative cable to the positive cable. (NOT the battery.) You will need a short length, (a foot or so), of light gauge, (14 to 18 gauge AWG, insulated stranded copper), wire to span between the battery cable ends as there is not enough slack in the positive and negative battery cables for the ends to touch each other.

Hold all together for about a minute or more, as you are discharging memory modules within the engine computer and elsewhere. Then it is suggested you just let all sit disconnected for say ten minutes prior to commencing to put the battery cable ends back on the battery posts per the following.

Reattach positive terminal to the main starting battery positive post.
Reattach negative terminal to the main starting battery negative post.

Start engine and hopefully no or fewer warning lights.
Reset time on the radio - note that the station presets are still there as not everything is erased. Nothing much else needs resetting either.

You can now connect up the other batteries if you have a multiple battery setup.

This is a link to a thread in disco3 re the hard reset procedure.

DISCO3.CO.UK - View topic - Hard Reset

This is a link to a thread on Disco3Club re the hard reset procedure.

Disco3Club The Discovery 3 and 4 Owners Club • View topic - How To, Hard Reset on a D3

That module is part of the dash ATCM module. Also does other things related to AC control, heat, etc. The schematic shows a high number of wires, and if you search the LR3 electrical drawings that same connector number shows up on other pages not related to seats.

So if that whole puppy has to swap, big $$. Salvage or dismantler? Probably have to be programmed even if you swap it.

But fuses in two places, battery junction box 7E, and Central Junction Box 28P and 51P.

Thanks guys for the info. I thought I had the seats fixed, but then they crapped out again. First, I did the hard reset with no positive results, although, I like knowing how to do this reset for future reference.

Next a checked the applicable fuses. The fuse locations from all the wiring diagrams do not seem to match the labels that are on the panels but I am confident there was nothing blown. Next, I removed the center console cover and then removed the climate control module. This was pretty easy. The C2295 plug which powers both of the front seat warmers was fully unplugged. I couldn't believe it. I reconnected the plug. The front seat warmers then work...for a few minutes. I am not sure if they went through a full cycle or if the just warmed up and then quit. Now, they are acting exactly as they did before. I checked all the fuses again and found nothing. Also, I checked the C2295 plug again. It was still connected. I disconnected and cycled powered. Then I tried the seats again and still nothing.

Here is my theory. The previous owner had seat warmer problems and couldn't figure it out either. He must have disconnected the power supply after giving up. That is my theory anyway.

Any thoughts on where to look next? Thanks again. -Matt

PS - bbyer, the link that you provided goes to a wheel spec diagram, but I managed to find the wiring diagram by doing a search on that same site. Thanks.

PPS- Savanah, in one of your other posts, you linked to a site where you could download the whole LR3 workshop manual. That thing is awesome. Thanks.

With a test meter, set for ohms, and that connector unplugged - read for ohms between pin 5 (green) and pin 13 (green and black). Compare to reading from pin 4 (green) to pin 13 (green black) - should be pretty equal, these are the heat sensors in the seats. If open or shorted could fool the module.

Now measure pin 6 (blue pink) to ground (metal frame of truck). Compare to same reading from pin 3 (blue slate) to ground. Should be the same, these are the heat elements. If one is a good deal lower than the other, that side would overheat. Perhaps there is an internal safety function in the module. You also have other connectors that would allow you to unplug one seat or the other for isolation testing.

Note: that won't be a long term solution. If SWMBO has to sit in the non-functioning seat, you'll be in the "hot seat" in more ways than one.

test the resistance in the seats. if its over or really excessive then its new ones. its a 45 minute to an hour repair but you need new hog rings. just remove the connectors and the four bolts that hold it on to the frame and you are done. then have fun with the hogrings.
This repair usually takes about forty five minutes maybe longer and trust me, no tech can make the time in the repair they say. it pays .5 warrantee and it can be done if you are removing the old parts and installing new ones.

Hello guys. I just wanted to follow up. My heated seats are working!!

During my original trouble shooting session, I did the hard reset mentioned above with no luck. Then I pulled the climate control module out and found the plug that supplies seat power disconnected. I plugged it in and then the seats worked very intermittently for a few weeks but didn't work far more than they worked. Next, at more advice posted above I wanted to check continuity and resistance from the plug behind the climate module. Before doing this, I performed the hard reset again just for the heck of it. I also opened the module itself to examine for any obvious damage. I found none. Also, my ohm checks were really inconclusive as I didn't really know the pin assignments and I didn't have a color version of the wiring diagram in front of me. But, when I put it all back together the seats worked and they have been working for a few weeks now.

Here is what I think happened. The plug was disconnected purposely because the Rover used to live in Houston were the seat warmers would just be annoying. This confused the system. My first hard reset didn't work because the plug was disconnected and couldn't properly discharge the system. Later when I did the second reset, the plug was attached and I think this properly reset the control module. Either way, the wife is ecstatic. Thanks for the advice.

Thanks
Matt

Appreciate the update.
 

It is nice to hear of success. I think your analysis may just be correct; still not certain why anyone would disconnect something even if it is not needed, but ....

Anyway, yes it often requires a few days for the various warnings to disappear from the systems or even for systems to get working again after being fixed. That is why dealers with the T4 will often clear the codes manually after a repair - to get rid of the indications of a problem. I also think that the hard reset can speed the process up as it can erase codes from some of the systems - sounds like the heated seats may be one of them.

I think I have heard of similar where guys replace the heated windscreen with a non heated but do not tell the computers that the 3 now has a non heated windscreen installed. Error codes start to show up. I do not know how the vehicle later reacts should a heated windscreen then be installed.

Thanks for the update particularily when it is a good news update.

Whomever looked at that car the first time was dumb. All he had to do was take the plate off and take the screws out. there are six screws to pull the entire atc out and then you are done. you can pull them out in five minutes and have it diagnosed from there. all he had to do was check there first. Sounds to me he just looked at the codes and wasted the time he charged you.

If I put a second hand ac control unit would it have to be reprogrammed to my car for the front heated seats to work as my old unit didn't have the heated seat buttons?