Originally Posted by fatty4x4
Is your truck a 1998? If it is you might get more responses in that area?
One usual suspect is a relay under the hood that needs replacing. It is overloading. The second place to look, which is more work would be a broke grid on the heated mat in the seat.Look for the relay first.
Ding, ding, ding... we have a winner here !!! ( at least close enough to what happens )
The heated seats have a tenancy to burn through the wire right where your thigh would be on the seat bottom.
Ford uses a single element through the seat bottom, that is hooked in series with the seat back, and 1 fault in the entire circuit, the seat turns on, and then shuts right back off. The heated seat module is what turns the element on, and controls the temp shut off. The LED on the seated seat button is the status reported back from the heated seat module.
This is why the status LED turns on and shuts right back off, it cannot find the heated seat element, and rather than risk starting a fire, power is shut off.
BTW: No relay with the seated seats, line voltage right to the seated seat module. The switch turns the heated seat module on & Off.
Quick test, unplug the heated seat module, and use a meter to check resistance of the heated seat element ( diagram in the thread above ). You will see a high resistance, but it should not show as open ( or a close to 0 ohm reading ). Watch your meter scale setting when testing this, you will need at least the K or M range ( 1,000 or 1,000,000 ).