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SD1too · 11th December 2019, 09:20

James,

I'm beginning to wonder whether you do have a fault at all. When I activate my heated seat straight after a cold start I don't feel warmth immediately. This is, of course, when the leather is extremely cold. As you say that both seats are affected, and as Ray has pointed out the two circuits are separate except for a common earth which you have temporarily replaced, it seems beyond the realms of possibility that both your heated seats have developed the same fault at the same time.

Attempting resistance measurements through the switch won't help. It's not a mechanical latching switch. As Ray says, it contains electronics, probably a timer similar to the HRW switch. The orange/white wire to pin 2 of the switch connector provides an uninterrupted supply for that and the LED.

With a cold seat and the ignition on you should see 12v on the yellow connection to the switch. When you operate the switch and the LED illuminates, your meter should show 0v. The seat should begin to heat but it won't be instantaneous.

Simon

11th December 2019, 09:20	#9
SD1too Doesn't do things by halves Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model. Join Date: Mar 2007 Location: Former Middlesex Posts: 20,374 Thanks: 1,587 Thanked 3,749 Times in 3,181 Posts	James, I'm beginning to wonder whether you do have a fault at all. When I activate my heated seat straight after a cold start I don't feel warmth immediately. This is, of course, when the leather is extremely cold. As you say that both seats are affected, and as Ray has pointed out the two circuits are separate except for a common earth which you have temporarily replaced, it seems beyond the realms of possibility that both your heated seats have developed the same fault at the same time. Attempting resistance measurements through the switch won't help. It's not a mechanical latching switch. As Ray says, it contains electronics, probably a timer similar to the HRW switch. The orange/white wire to pin 2 of the switch connector provides an uninterrupted supply for that and the LED. With a cold seat and the ignition on you should see 12v on the yellow connection to the switch. When you operate the switch and the LED illuminates, your meter should show 0v. The seat should begin to heat but it won't be instantaneous. Simon __________________ "Whatever is rightly done, however humble, is noble." Sir Henry Royce.