folks,

my x300's front and rear heated seats do not seem to be operational... power seat incl. memory function is fine

• the little red lights on all 4 (fr and rr) switches come on when pressed
• all 4 relays click
• fuses are fine

I find it strange that all 4 heating pads my have failed simultaneously. Looking at the electrical diagram, however, I do not see a common power source or common ground...

any thoughts?

thanks in advance

 

hi

I looked at the wiring diagram, and there are 2 wires (in/out) of the body processor module

per the diagram I found online, 1 wire goes from BPM to the seat module (wire has continuity/not cut) and the other wire goes from BPM to the switch

these 2 BPM wires are supposed to be + when inactive and ground when heated seats are active, but they don't show ground when seats are active... faulty BPM, right? problem fixed... that's what I thought...

... tried 2 other BPMs (matching #) and none show ground either... could all 3 BPMs be bad?

the other thing I was thinking is: The 1 wire going from switch to BPM is supposed to be BPM input and supposed to provide BPM w/ ground when active... this ground supply cannot come from anywhere but the switch... if there is no ground, would it make sense to assume the switch panel is faulty? I have a spare one I can swap, just not looking forward to removing the ski slope and radio, etc

• switch activates (lights come on)
• relays click (all 4 seats)
• no heat!

I took the seat out to check continuity in the heater element, and it's more confusing down there...

there's 1 plug with the following orientation:

red wire (from module .. shows power)
red wire (disappears in the seat)
---------Plug----------

these plugs connect together

---------plug----------
red wire (disappears in the seat)
black wire disappears in the seat)

how do I measure the continuity in the seat elements? I have 3 wires going the seat (not 2), but the diagram shows 2 wires for the heated element

so do I need to try a 4th BPM? a new switch? new seat pads? new X300? lol

thanks

 

This won't help but.....

I couldn't get my head fully wrapped around the logic of the circuit, either. And the seat connectors had me a bit baffled as well but I eventually figured them out....but I can't begin to remember any details that would help you, sorry

In my case all four heating pads were literally burned out. I installed aftermarket pads which work fine. Oddly, the only way I could make them work was to ground them independantly of the OEM wiring. Once I got 'em working I "called it good" and didn't have the time or interest in figuring out why they needed their own ground circuits.

Cheers
DD

 

thanks Doug, .. if I have to replace the pads on all 4, I will keep your advice on having a separate ground in mind ...


edit:

where was the seat back (squab) ground outlet (the grey plug that's for the seat back)? (see my post below)

 

turns out it's the heated seats elements... will need to source replacement...