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Procedure to Repair Heated Seats

Jagmeister

NAXJA Forum User
Repairing Heated Seats

The following details my experiences in repairing the heated seats on my wife's 1998 Grand Cherokee.

The repair turns out to be fairly simple once you know how to go about it. My son and I fixed both the passenger and drivers seats and the problem was the same on both.

The actual problem occurs in the wiring inside the seat cover. This sounds like an unfixable problem but it's surprisingly easy to get at. There are two heating elements (small thin wires looped through the seat cushion) in the seat. The one that breaks is the one on the outside (door side) edge of the seat. This makes perfect sense if you think about it. Every time you get in and out of the car you put a lot of wear and tear on that outside edge of the seat. There are two heavy gauge wires coming up into the seat and they are soldered to the thin wires about 2/3rds of the way back from the front of the seat. In both cases, the break in the thin wire was within a few inches of the solder joint.

Before you get started with this verify that this is the actual problem with your seats. Find the relay under the seat and remove it (see steps 8 & 9), and test for continuity between the BLK/ORG and BRN/BLK wires. If it tests good then the break may be in another element. The wiring diagram at the end of this article may help. They are wired in series so if one breaks the other won't work either. Odds are pretty good the problem is in the seat.

Tools needed:
1. Phillips Screwdriver
2. Pliers
3. Soldering Iron
4. Continuity Tester (Multimeter)
5. Heatshrink tubing or electrical tape
6. Needle
7. Small utility knife

Procedure:

1. Put the seat as high up and far forward as it will go to give some working room underneath the seat.
2. Remove the plastic side panel from the seat that holds the seat power adjustment knobs. (Three screws)
3. Look under the seat from the front and notice the long white plastic clips that attach the seat cover to thin metal rods. Unsnap the plastic clips on the front and console side of the seat. (you may need to deal with a couple of upholstery staples, just twist them off with a pair of pliers)
seat-clip.jpg

4. Now on the door side there is a small plastic clip holding the seat cushion to the metal, up towards the front, that must be pryed out.
seat-side.jpg

5. At this point you can roll back the seat cover starting from the front. BUT! WARNING! on my seats the actual seat cover is velcro'ed to the foam cushion.
seat-velcro.jpg

6. Very carefully work the velcro free as you roll back the seat cover. If you just yank it it will rip the bottom part of the velcro strip right out of the foam cushion (ask me how I know),
7. When you have rolled it back as far as it will go you should find the wires coming up from the bottom of the seat. They are covered by a small patch of cloth which is glued to the seat cushion. Carefully separate the cloth from the cushion exposing the wires. I found it necessary to use a small utility knife to help slice the foam and uncover the thin wires. You will probably want at least 2 or 3 inches of thin wire uncovered.
seat-wires.jpg

8. Now go back under seat from the back. Look on the door side seat rail for the relay. It is attached to the rail with a metal clip which looks like it should pop right off real easily. It doesn't! You have to work at it some. Once you get it unclipped pull it back out as far as you can so you can work with it.
9. Remove the relay from the connector and find the black wire with the orange stripe. Use a paperclip or other probe and connect one end of the continuity tester to the BLK/ORG wire terminal.
seat-relay.jpg

10. Now test the two heavy wires you just exposed in seat cushion and find the one that provides continuity. To find the break we are going to work our way up the thin wire until we lose continuity.
11. Hold a sewing needle against the probe and push the needle into the thin wire. (just beyond the heavy wire) You should still have continuity.
12. To find the break in the wire you simply move the needle further down the thin wire testing for continuity as you go. When you no longer have continuity you have located the break.
13. Cut the bad part out and repair the wire. Soldering and heatshrink tubing are highly recommended.
seat-repaired.jpg

14. Consider the fact that there may be more than one break in the wire before you go putting everything back together! This is easily tested. Go back under the seat to the relay connector and use you continuity tester to verify continuity between the BLK/ORG and the BRN/BLK wire terminals. If there are no further breaks you will have continuity, otherwise go back and use the needle to find the other break.
15. You can plug the relay back in and test it now to see if the seats heat up.
16. Reassembly is the reversal of the above steps.

Partial wiring diagram shown below:


seat-wiring.jpg
 
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