[ehalverson]

I wish I had discovered this going into winter rather than going into spring, but at least it'll be good knowledge for next year. Also not sure that this is the best place for this post, but....

The seats heat up 2-3 times faster when the air heat is off! At first I thought I was crazy but I've tried it several times both ways now and it's true. It makes sense, but it's disappointing that the electrical system wasn't set up better so that it wouldn't matter. I'm surprised it makes that much of a difference as I leave my heat on auto for 68-70 and it doesn't really kick in till the engine is good and warm, but even at that low setting it just draws too much power for the seats to warm up fast.

My car is an '06 XT with leather seats and dual climate control, I'm not sure how true this is for other models.

 

[tdelker]

Interesting...
Do you also have the very common failed bottom seat heater element? I do... Got all summer to fix it though

 

[ehalverson]

Nope, everything works just fine. It all just works faster when it doesn't have to compete for power.

 

[plain OM]

The seats heat up 2-3 times faster when the air heat is off!

I'm surprised that it's that noticeable.

The seat heaters are powered through fuse #17 (15 Amps) in the in-cabin fuse panel. Fuse #17 only supplies the seat heaters. It's connected back to SBF-2 (50 Amps) in the engine compartment fuse box. SBF-2 powers a number of electrical functions, including the trailer connector (Wagon model), Stop light & brake switch, and the Wiper de-icer relay.

The automatic climate control (fan, compressor etc) isn't connected to the same SBF circuit/branch.

Also, the seat heaters aren't electronically integrated with the climate control in any way that would cause one to operate at reduced effectiveness when the other is on.

I'd make some voltage measurements to confirm whether the power (Voltage) to the seat heaters is indeed significantly lower when the climate control is turned on.

 

[rasterman]

Even though the fan cuts back at low engine temps, ANY air moving is going to make you feel colder. I doubt the seat heater is working any better, but at least the dashboard fan isn't robbing you of heat.

 

[ehalverson]

I'm surprised that it's that noticeable.

The seat heaters are powered through fuse #17 (15 Amps) in the in-cabin fuse panel. Fuse #17 only supplies the seat heaters. It's connected back to SBF-2 (50 Amps) in the engine compartment fuse box. SBF-2 powers a number of electrical functions, including the trailer connector (Wagon model), Stop light & brake switch, and the Wiper de-icer relay.

The automatic climate control (fan, compressor etc) isn't connected to the same SBF circuit/branch.

Also, the seat heaters aren't electronically integrated with the climate control in any way that would cause one to operate at reduced effectiveness when the other is on.

I'd make some voltage measurements to confirm whether the power (Voltage) to the seat heaters is indeed significantly lower when the climate control is turned on.

I was unaware of that many of the details, but this makes me wonder if my alternator could be going and the car as a whole just isn't getting enough power.

Also the wattage is more likely than the voltage to impact a heating element, and to measure that I'd have to break the circuit which I'm not exactly eager to do just out of curiosity.

Everyone who has heated leather seats in an 05-09 - How long until your seats start to feel comfortably warm (not tolerable, but warm like you don't want to leave) after starting the car in 30-35 degree temperature in the dark? I haven't timed mine but playing with google pedometer I get about 1.4 miles with the fans off, or 2.5 miles with them on driving in the city with lots of stop signs, lights, and traffic in my morning commute. (so my initial estimates of 2-3 times faster were off)

I wish they were faster like some newer cars, but I'm just glad to have them again.

 

[Looby]

Also the wattage is more likely than the voltage to impact a heating
element, and to measure that I'd have to break the circuit ...

Nope, voltage is all you need. For a resistance heater, watts and volts
are joined at the hip. You can't increase/decrease watts without moving
voltage in the same direction (and by very nearly the same amount).

...not just a good idea, IT'S THE LAW!

Looby

 

[4wheeldog]

After reading this thread a couple of times over several days, I believe the OP has found a red herring. It may seem that the seat heats quicker/hotter without the car heat on, but there is no evidence that it works that way.