Sounds like your auxilliary water pump has frozen up and damaged the circuit board in the pushbutton controller. Was the damaged trace in the circuit board the one which runs right along the very back of the board, from one side to the other? If so, this is the one which drives the aux water pump.

The aux water pump is a small electric pump connected to the engine cooling system. It feeds a constant stream of hot water (coolant, really) towards the cars heater. The intent is to feed a healthy quantity of hot water to the heater even when the engine is running at low speed (such as a traffic light). At such low speeds the engine's own mechanically driver water pump doesn't move enough hot water to keep the interior toasty warm.

You can unplug the aux water pump to see if the controller behaves any better. The pump is located under the hood, in the front, passenger side corner of the car. Look for some water piping coming straight over from the front of the engine. It connects to the pump, which is a black, about 6 inches long, and has an electrical connection. From the pump water piping heads straight back towards the passenger compartment. There is an electrical plug at the aux water pump - just disconnect it.

If you live in a climate where winter is not too harsh, you can just do without the aux water pump. However, if you live somewhere seriously cold, it makes life a bit nicer. The partsshop on this site has them for $138 (which surprisingly isn't a competitive price - they usually do much better.)

- Jim