Dash toggle lights up. But, the driver seat heats only intermittently.

Where does one begin the search for the culprit?

 

Well, many intermittent electrical problems with seats seem to stem from the under seat wiring and connectors. I'd check for loose or corroded connectors, then chafed or trapped wires caused by years of seat adjustment.

 

good advice armstrong!

 

In the driver's seat?

It has to be a loose connection, damaged harness or damaged heater element.

Graham

 

I would start by suspecting the control modules. The easiest way to find out is to swap the modules between driver side and passenger side, and see if the heater problem "moves" with the modules. The modules are grey plastic boxes held by 2x10mm nuts, right under the front edge of the seat cushion. The seat does not have to be removed, this is probably a 20 min DIY job.

Best of luck, keep us posted.

 

I too would go for the module first. I just had one go bad and the first indication was that the passenger seat heater was inop. Then I realized that the adjustment controls for that seat were also dead. Turned out to be a couple of circuit board traces that had corroded through. Pretty easy fix. All is well again.