Sounds to me lime you have a "hot spot" or several - classic symptoms unfortunately ......
On Leather and Elite (cloth & leather) there is a
stranded heating element woven into thin padding in the seat cover. On non-Elite seats the heat comes from a single wire element incorporated into a cloth "mat" which fits between the seat cover and the foam cushion.
With the stranded elements, individual wires break with time and mechanical wear and tear. So, very gradually the hot spots develop as you are finding. More wires break/melt and eventually the circuit goes open circuit and stops working totally.
With heater mats the single heating wire is much thicker and therefore stronger - but if that single wire breaks then the whole seat stops working as the base and back are wired in series.
On seats that I have dismantled to fix (can only fix non working ones) I have seen the hot-spots and burn marks. Problem is that a fix usually just moves the hot-spot somewhere else and it will fail again before too long
.
The good news is that the way to fix them is to put heating mats between the seat custion and the seat cover. It works, I've done it
. Finding the pads might be a problem due to stock availability - or strip them from a working seat in a breaker.
Stripping seats down is very fiddly
. There is a guide which shows you all you need. Don't underestimate how much time it takes though .......
A few assorted comments:
1) Elements must only come from like for like models - i,e, PFL, MFL and FL.
DONT mix them up.
2) Dont switch the ignition on with a seat removed from the car - if you then the airbag light will come on and wont go off again unless reset by a code reader/tech 2.
3) On PFL seats the pre-tensioners are mechanical and must be locked to prevent activation - there is an attached red plastic gismo to do just this.
4) MV6s are the exeption to the cloth/leather rule - with both having heater mats, they also have an extension into the knee bolster.
5) As a check, a working seat takes about 5 amps when working correctly.
6) After-market kits can be fitted if the GM ones prove difficult to get hold of.
And finally, I have a very small stock of MFL pads available if anyone is interested. I have tried selling them on the parts section but have had no takers so far
HTH - Rob
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Topic: Heated seat egg cooking issue (Read 1875 times)