Here is my dilemma.
I have an 04 F-150 Lariat with heated seats. Driver side works just fine. Passenger side i hit the switch, lights go on and then off. Swapped the heated seat modules figuring that since the modules are the same then the driver side would not work and the passenger side would. Well that didn't work. Neither side worked. Lights on the switch would just turn on and then off immediately. Swapped the modules back to original positions, driver side works fine, passenger doesn't. Fuse 18 (10A) checks out fine to each of the connectors underneath the seats (12V in start). Fuse 118 (30A) checks out fine to each of the connectors underneath the seats (12V all the time). Pins 6&7 on both connectors tone out as closed and read the same (about 3-5 Ohms I think it was). Performed the EATC module self test OFF-DEFROST-AUTO and was all good, no DTC's. Performed the EATC test OFF-DEFROST-RECIRC and got 22 celcius 66 celcius 16 celcius and 76 celcius. Ford techs had no idea when i asked about those continuos DTCs. The only thing i haven't checked is the switch to the passenger side. Wanted to see if you had any ideas before i tear in to that. Any help would be greatly appreciated. Wife is busting my chops cuz her butt warmer won't work.

 

im really surprised, someone here joins and has actually done preliminary testing. instead of coming here and going, my *** warmer wont work, fix it for me. well done sir.

i have no knowledge of the system, both of mine work, ill be watching responses.

good luck.

 

SSCULLY-You mentioned a possible problem with the seat temp sensor on the passenger side-The thermistor that makes up the heated seat sensor is pins 3&4 towards the seat side of the harness.
I don't know what the reading should actually be. All i know is that the resistance should go down as the temperature increases due to current flow I would assume.
Well the driver side (working side) reads 12.9 K Ohms. The passenger side (non working) reads 15.4 K Ohms.
Plugged the modules back in, driver side no problem-passenger side switch lights just turn on and then off. Any idea?

 

You need a new seatheater pad. I heard the ones from Rockauto are better than the OEM Ford ones.

 

The temp sensor is an on / off ( so once it reaches a temperature, it signals the heated seat module to shut off the seat.

When you took the reading on the temp probe, was the seat empty, or did you have someone sit in it.

Same for the seat element. If the seat was empty, it could be the seat has an open that happens when there is a body in the seat.

The status light going on, then off is an indication that either the element is broken or the sensor is signaling that the seat has reached temp for the module to turn it off.

https://www.f150online.com/forums/me...clim-seats.jpg

The switch is just a momentary switch that pulses the heated seat module for high - low or off. If the LED status comes on, this is the heated seat module signaling that the command was started ( even if momentary ).

 

SSCULLY-Took measurements on the thermistor circuit and heating element circuit. Thermistor readings were the same with person in or out of seat. Heating element circuit toned out as closed with person in or out of seat. Decided to break in to the switch portion. Cabling looked factory new other than some dust. Toned out the cables leading from the EATC Module (Pins 15,16,17) to connector under the passenger seat (Pins 8,9,10). All toned out and checked out good. Swapped modules again after playing with the cabling and again neither side worked. Put them back, driver side fine, passenger nothing, light just goes off and on. Before I break down and buy a module is there any way of getting a schematic of the Heated Seat Module itself to try and trouble shoot it? Or is it even worth the effort and i should just buy the module. I can't think of anything else that it could be.

 

I did notice one thing. When putting the passenger (bad side) module in the drivers side the switch light will stay on maybe 2 or 3 seconds then go off. When either module is on the passenger side it goes on and off immediately.

 

Ford does not supply diagrams for the module itself, those are made to be changed once diagnosed.

The part that has be wondering is why when the driver's side module is installed in the passenger side, it still does not work. That points to a problem with the seat itself ( which appears to test good ). the driver's side not working with the passenger module installed, points to a bad module.

When you measure the seat for resistance, is it really 5 ohms both sides ?

 

SSCULLY - It's been almost 2 years since I messed with this and I'm determined to fix thi s heated pass seat problem. Re-checked thermistor readings (Pins 3&4) 4.8K Driver side 6.6K Pass side. Toned out Pass side heating element (Pins 6&7), no open circuit. I jumped, pushed, rocked in that seat and the circuit never opened while toning out.
New: Following Chiltons schematics i discovered this, on the drivers side module connector, Pin 5 is VPWR (Hot in start or run) and Pin 12 is VBATT (Hot all time).
The passenger module connector shows Pin 5 as VBATT but it's fed from F2.18 10A (Hot in start or run).
The passenger module connector shows Pin 12 as VPWR but it's fed from F2.118 30A (Hot all time).
I double checked this and it is in fact wired that way. So that means the heating module internal circuitry would be different for passenger side from driver side. I figure that is why putting the good driver side one on the passenger side would not work. The feed was different somehow. I don't know.
Why would they do that baffles me but that is where i'm at now. Thinking about just buying the module as i can't think of anything else that it could be.