I have a 2002 Screw with heated seats, the only problem is the heated seats dont work. I was wondering if anyone has a wiring diagram? Do they use any sort of a relay?

 

Is it both, or one that does not work ?

Did you check the fuse for them, if it is both ?

 

Both seats do not heat, and the fuse is good.

 

How did you check the fuse ?

Under the seat, is the connector for the heated seat module.

Check for the power on connector with the hot in run position pin.

 

Alright, I went to check the power on that connector, and noticed that the connector for the heated seat module is not the same as that picture, mine is 6 pins wide, by 2 high, total of 12 pins. The wire colors are the same as that depicts, but I still dont have power on pin 4(hot at all times) or pin 6(hot in run).

What position is the heated seat fuse at? I just want to make sure I'm checking the right fuse, although all the fuses under the dash are good. Are there any relays for the heated seats?

 

owners manual shows 2 fuses for the heated seat.

Hot at all times pin #4 is from the Battery Junction box ( aka BJB or engines compartment fuse panel ) Fuse # 118 30 A. Owners manual page 214.

The hot in run position pin #6 is Central junction box ( aka CJB, cab fuse panel ) fuse #23, 10 A. Owners manual page 211.

If you do not have power at those pins, either the ground you were testing with the meter to is not a good ground, or the fuses are not good.

 

Checked fuse #118-30amp, found it to be burnt out, fixed my pin 4(hot at all times) voltage, as it now reads 12v.

I still do not have voltage on pin 6 on the connector, my fuse #23 is good.

And I've used multiple grounds all to get the same effect on the voltage meter.

 

Dumb question ( so forgive me ) but you do have the ignition key in the run position when you are testing pin #6 ?

 

Key is in the run position when testing pin #6.

 

Swap Fuse #23 then, it is not good, or the wire is broken.

 

I have already tested the fuse, I have 12v on both sides with the power on. I'm going to pull the seat some time this week to gain access to the wiring and i'll go from there.

 

Pull the connector off the heated seat module and pull fuse #23, and check from the device side of the fuse to the heated seat module connector pin # 6.

Might be able to get the meter to stretch that far ( just form the dash to under the seat ).

That would tell you if the wire is OK.

 

Tested the wire, found that when I moved the connector around at the seat, that the resistance would jump around, removed the harness from under the seat, and found a few hard bends on just the wht/bl wire, it was longer than the rest by about an inch and a half. So I pulled the pins out of the connectors and ran by the shop, luckily we had the same connectors in stock(I work at a Volvo/Mack heavy truck shop as a tech). Replaced the wire and retested, continuity no matter how the wire is moved. Retested with the seat button and still no heat in the seats.

Stupid question, but on the switch, is there a light? It looks like there is a light, but I want to make sure that it actually lights up.

This is leading me to believe that the modules are bad. I tested all the wires for continuity throughout the system, all are good, and look good(I pulled all the loom off).

Next question, the switch has 4 wires running into it. One will obviously be power, and two I'm guessing run to the elements in the base/back of the seat. Is the fourth just a ground?

 

My '01 had an operation status LED. It was yellow I think

If you think you have a problem with the heated seat module, swap in the one from the passenger's side ( if that one is operating correct ).

The connectors show 1:1 on the pin outs




Same for the switches, 1:1 pins.

The heated seat switch has 4 pins ( in a 8 pin connector 4 unused ).

pin 1: WH/BL - hot in Run
pin 2: DG/VT - cushion Enable
pin 4: OG - modules to switch
pin 6 : WH/LB - hot in Run

From the diagram, one of the WH/LB to OG is the status LED ( in the 2001 EVTM ) and the other other is WH/LB to DG/VT

So the status LED seems to be WH/LB to OG which is pin 10 in the heated set module. Kind of press the button to turn it on via the DG/VT, and the module if running must switch ground back on the OG wire. When the seat heats up to temp sensor max, it shuts off, and removes ground from the OG wire.

Maybe try the driver's side module in the passenger side, to see fi the module is operating, and it is a problem with the temp sensor in the set cushion ?

Seat cushion is heated seat module pin 7 ( black w/ light blue ) to pin 1 Brown w/ light blue. Check the resistance on that pair for an open. The symbol looks to be a thermistor. Confirm the readings on the passenger side.

I have seen posts where the set cushion "wire" is broken around the edge of the set by the thigh area. This was a case of it went on, but did not get warm.