SWMBO called me at the airport on Tuesday to share that the HVAC was not working. Nor would the unit heat. As I was stuck in Detroit for the week, she just left well enough alone. As I ruminated over the situation while entertaining customers, since both heat and cool were not working, this to me ruled out a low pressure refrigerant issue. I was worried about low refrigerant as the system has a very slow leak. In the peaceful morning today, I checked a few things. Many years ago I had found a failed tiny 3A automotive fuse in the air handler would cause the unit to stop working. This fuse was OK, though. I operated the power switch on the line leading to the HVAC. It felt strikingly useless. No click, no spring force, no nothing. Opening up the box, and pulling the switch outwards, it was obvious. In the power line to the upstairs furnace / AC unit, this switch finally gave up after some 16 years of non-use. It of course is never actually switched off. One of the two leads was not attached anymore, and the other was cracked and loose. The installer used the quick-and-easy method of inserting a stripped wire end into the cheapest switch that could be purchased. A new HD switch, and leads that were hooked around the brass screws and the system works again. I reckon that the years of hot and cold attic conditions coupled with some electrical heating did the switch in.

This message has been edited. Last edited by: 4MUL8R,

Interesting failure, do I see some melting of the plastic? Maybe arcing? I hate push stubs.

Congrats on a diagnosis well made! So many people start at the hardest thing first.

The switch may get used when changing filters ... or maybe not?

I shut off my heater in summer, in case someone turns up the thermostat by mistake.

Is the switch rated at a high enough amperage for the HVAC unit it is feeding electric to?

ANY 15A switch will be fine for a furnace.

Glad you got it up and running without an expensive service call.

Very common problem. See the broken piece has a 'L' shaped piece on it. That along with a strip of metal in the switch for a Chinese finger trap that holds the wire in place. They fail all the time. As Excam said any 15a rated switch should work just fine. The heat is produced by the gas, that is the energy required for heat, the only energy going through the switch is for the blower fan and is likely around 5-7 amps max (excam can give you better idea).

It looks like it might be 12awg wire that is connected to the switch. If that is the case the stabbing of the wire into the back of the switch caused the failure because the switch is only rated to have 14awg wire stabbed into it.

You did the right thing by moving it to the screw terminals. I would not look any further into it, problem solved.

For anyone else reading DO NOT use the stab in method, they will fail, always, every single time they will fail. Just a matter of time before they do.