In the morning my seat heater takes several miles to warm up, but in the afternoon I can feel it heating before I get down to the end of the block.

This seems to happen even when the outside temp is pretty much the same.

Any ideas ?

 

This is the only thing I can think of -- could it be that the temp inside the car is higher in the afternoon (from the sun or whatever) than in the morning, even thought the outside temp is still cold? If the heaters were cheap, I'd replace them just to see if it helped. But having bought and installed a set, it's a lot of work and each one is several hundred dollars, as i recall!