Under the Hood: Truck’s seat cushions heat up unbidden – Greater Milwaukee Today

Q: I have a 2003 Chevrolet Silverado 2500 HD Diesel. My problem is that the heated seat on the drivers side comes on with no demand. I removed the door panel and disconnected the plug at the switches. The seat is eliminated from heating, but the rear back cushion heats up, sometimes intermittently. Which wire do I disconnect under the seat to eliminate this?

Ted

A: I dont get a chance very often to help someone try to make something stop working!

Your Silverado seat heaters are a fairly complicated system; seat cushion and/or back heat request switches tell the drivers door module to move on this. After communicating with the powertrain control module to be sure the engine is running, the door module sends a class 2 serial data message to the drivers seat module, which controls the heaters by supplying both power and ground. Thermistor sensors within the seat cushions provide feedback so the proper heating level can be maintained.

Without detailed testing, its difficult to imagine how the seats are mistakenly being heated. A pro grade scan tool can be used to observe inputs and outputs of both the door and seat modules, which would narrow the suspect list considerably.

A surefire way to cease operation of the drivers side heaters only is raise the seat fully for access and unplug connector #325, which is located roughly centered, two-thirds of the way back, beneath the seat cushion. This connector contains six wires; hopefully, the wire count will help differentiate it from the three other connectors somewhat nearby. The purple wire within this wire group provides ground for the seat back. Could it be chaffing on nearby metal?

Q: Your headlight lens article got me thinking. I have an older car with good quality halogen glass headlights and they could always be brighter too. What do you think of a relay kit? Do these really help with brightness?

Sid

A: Vehicles with the older/traditional sealed beam headlights can often suffer from voltage drop in the headlight circuit, due to skimpy wiring diameter, dirty contacts in the headlight and beam select switches, as well as in line connectors. Lets say your system voltage is 14.6 volts (engine running); you might find only 12.5-13 volts are actually making it to the headlights, resulting in slight to moderate dimming.

A relay kit, or a carefully home crafted equivalent, uses the original headlight circuits to energize a relay, which delivers a shorter/more robust circuit directly from the battery to power the lamps. Done right, fuse protected, wiring carefully routed and with good connections, this can reduce the voltage drop between the battery and headlights to perhaps 0.2 to 0.4 volts (14.2 now delivered). This can bring up brightness by perhaps 15% to 20%.

Is it worth the trouble and expense? Some think so, particularly if their original circuit is suffering worse than mentioned.

Im receiving some great feedback regarding home remedies for clouded headlight lenses. Ill follow up soon with these recommendations!

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Under the Hood: Truck's seat cushions heat up unbidden - Greater Milwaukee Today