I got to be honest, I should have done this years ago, but procrastinated and kept finding excuses not to mess around with it.
To get started, this applies to climate controlled seats only, those that have heat/cool rotary switch with 3 positions each.
My symptoms were as following, turn either heat or cold, the switch light gets illuminated for a few secs and then goes off.
What confused me, is that this problem was fixed at least twice for me under warranty, both times the dealer replaced bottom cushion.
Both times, the feature then worked for some time, only to inevitably fail.
To get started, download your year's service manual and find SE (seat) file. It has all the electrical diagnosis diagrams and pinouts that you need for this job.
If you are not comfortable working around wires, I suggest disconnecting your battery. I did not.
The seat is bolted down by 4 bolts, 2 16mm head bolts upfront and 2 T50 torx bolts in the rear. The bolts are under plastic trim covers. Be careful to remove those
and not break the hold down clips. In my case, dealer overtorqued rear bolts, and I ended up stripping one out. I got two replacement bolts (part number 86899-79910).
After bolts are out, simply tilt the seat back to expose the bottom. It helps to put something to keep the seat tilted back to prevent it from falling on your head.
You may want to disconnect harness hold down clips from the front of the seat to give you more room to work in. In my case, dealers mechanic made an absolute
mess of wiring clips and routing, so I took time to properly reroute the wires and secure broken down clips.


View of the bottom of the seat tilted up

Above is the picture of what your seat looks like under.
My initial hope was that my seat filter was plugged up solid, I owned my car since 2008 and never replaced or washed this filter.



Outside view of seat filter. This is prior to me washing it

Inside view of seat filter.


Filter was indeed dirty and I took my time to wash and dry it, but you can definitely reuse it, which is what I have done.
Meanwhile, I pulled the filter out by twisting it, and tested the seat function again. What I observed was, that the fan moved for a few secs, and then shut off.
It would do it in both heating and cooled modes. Restarting the car restored the function.

Reading through service manual it became clear that there is some safety mechanism that is shutting the system down, because the system works for a few seconds.
Next comes the actual troubleshooting.
Again, service manual to the rescue. It has a decent flow chart, that has you testing wire integrity, switch integrity, and expected values on both TEDs (thermoelectric device)
Climate controlled seats use 2 separate TEDs one for the bottom cushion and one for the back cushion. They either heat up or cool down, and then the air is drawn by fan
through the filter and ductwork and through those two TEDs.
There is safety logic that looks at temperature outputs by both devices and if they differ to a certain degree, the system gets shut down.
So I basically followed the step by step directions from the troubleshooting section. I used regular multimeter, but I have a nice AESWave connector pinout kit that makes it
easy working with different wires and not destroying them in process.
There are few various systems under the seat, so take time to orient yourself and understand which connector needs to be evaluated.
In general, if your wiring is undisturbed and seat switch does come on, most likely case is that one of the TEDs failed. That is exactly what I found out.
In my case seat back TED device was not reporting expected values 0.9-10ohm on pins 1 and 2. I had 211 ohms and that is definitely out of spec.
If you so desire, its very easy to remove the bottom TED out. Its held down by two phillips screws, disconnect the plug and remove it from the seat.
Then you can test it out directly at TED's own harness. It only has 4 pins. Pins 1 and 2 are expected to have 0.9-10ohm, and iirc pins 3-4 are expected to be in 1.1kOhm range, temperature dependent.

Here is bottom cushion with TED removed

Bottom of the seat with TED removed



In my case, I tested both TEDs based on Service manual pinout diagram, so there was a remote chance that there was a wiring issue from the seatback, so next challenge is to remove the rear cover, exposing
the back of the seat.
The manual had a vague instructions to get the cover off. There are 3 sets of clips that hold it down. Here are pictures to make it clear. But you first remove the bottom set, by pulling bottom toward back of the car,
then push down on the assembly to clear top cleats, and finally try to unclip center clips. I used long prybar to assist in the last step.


View of seat back cover

bottom clips

middle clips

top clips


When cover is off, you are greeted by something like this

Seat back view. Ductwork going into seatback TED.


Remove the TED and you are left with

Seat back TED removed


Here are the TEDs. The right one is the new part number, I got to replace the one in the middle.


TEDs. Left is the old bottom, middle is old back, right is new back.

Look inside the TED, its just copper radiator with 4 wires.


The TEDs for bottom and back are physically identical, the difference being the harness wire length. So there are two unique part numbers.
There have been multiple revisions of these parts. Go by part diagram on Nissan site when ordering new one. Looking at my
old part numbers made no sense, as they seem to be mislabeled. I even thought dealer accidentally swapped the two, but no, longer harness part goes into
the seat back, and shorter goes into bottom cushion.
I tested the new part and it reads in spec to what Service manual said. I assembled the seat and tested it out.
Confirmed fix and I got my climate seat functionality back.
Finally put everything back in place, torque 4 seat track bolts to 37 lbs/ft.
Enjoy summer!

 

Glad to hear you got yours working. Mine did not work because some of the tubing/vents and parts holding them in place were left off the seat bottom during the assembly.of the drivers seat. Nissan dealers and Nissan corporate were useless to get it repaired. I will never buy a Nissan again. If Nissan goes out of business, they deserve it.

 

yes, we went back and forth with you back in 2015. Apparently my seat has the necessary fittings, so I was kind of bummed at first seeing everything is in order.
I don't understand how the dealer fixed the system with replacing bottom cushions, unless they have been replacing the TED as well.
I agree with your sentiments on Nissan, except same pretty much applies to any car manufacturer.
You are at a mercy of a dealers' tech. Some are good and some are not. The warranty pay is garbage, so you get these half assed repairs.
My seat airbag harness was misrouted, and its sheer luck that I did not chop it in half adjusting my seat.

 

I agree that other auto makers may be just as bad as Nissan. But I figure they probably can't be any worse. I think in the future I would trust Toyota. Maybe they still care about building a quality vehicle. Also I would consider a used car that is out of warranty. I will repair it myself or find an independent shop that I can trust. That way I'm not stuck counting on a dealer or corporate to do the right thing.

 

Fantastic write up, thank you so much for taking the time to write this up. I needed this.
For some reason, I can't see your pics, but it's probably something on my end,

 

I updated the post and inserted images inline. Let me know if it works or does not.

 

Great Job on the write up and diagnostics! Giving DiagnoseDan a run for his money!

 

Bro... There's a filter in there!? My heat works good but every time my boys catch that cool breeze in a customer's ride I get all jelly cause my Max just doesn't hit me in the feels the same way. Gonna go pull mine in the dark right this minute!