Greg.Randall

February 7th 2026

So two nights ago the heat went out in the middle of the night. Not super crazy- it’s been running 24/7 for almost two weeks.

I flipped the breakers. Didn’t change anything. Set the space heaters up in the bedroom and went back to sleep, thinking it was probably gonna be an easy fix.

Next morning I pop the air handler open and check- we’re getting voltages in the right spots. 240v, yep. But looks like a fuse popped.

Weirdly uses standard automotive fuses. I go try and steal one from the car, but it’s a 3A and the car doesn’t have any of those, so I get a pack from the auto store. Figuring poor, tired HVAC just blew ’cause it had been running forever.

Pop a new fuse in, turn the breakers back on, and the thermostat turns on for one SECOND then the fuse pops.

Take the thermostat off the wall and pop in a new fuse, turn everything back on – fuse does NOT pop. So — either the thermostat’s shot or something it was trying to turn on popped the fuse.

Start multimetering everything. Unplug the thermostat wires from the control board side on the air handler and FML- two of the wires are dead short to each other. How does this happen it’s not like I accidentally went under the house and put a nail through the wire.

Sooooo I need to run a new wire.

Which kinda checks out. When I put this new thermostat in a month ago or so, there was an ULTRA sketch wire in there that I’ve been affectionately calling “mummy wire.” Wire from the olden days, when you wrapped copper in cotton.

The thermostat I have needs six wires, and this mummy wire was being used instead of one of the six from the proper cable.

So I gotta run a new wire from the thermostat to the HVAC. Go to Lowe’s and buy some 18/7 (18-gauge, 7-conductor) wire, 50 feet. And I start pullin’ cable.

For the thermostat area, I can at least use the old wire as a pull cable. I tie some paracord to it and pull that into the crawl space, then I cut the old wire off the paracord and use the paracord to pull the 6 feet of cable or whatever back up into the wall. (Did it in that order so I didn’t have to pull 50 feet through the hole in the wall.)

Crawl space is much less gross than average, with a pretty recent vapor barrier. But I get like 25 feet from the hatch and SOMETHIN’ SCUTTLIN’ ABOVE ME ON THE DUCTS.

I slide back to the next closest area with more headroom. Get my legs bent up so I can kick whatever is stalking me.

But the noise stops. My heart slows. I go back to pullin’ cable.

The back part of our house has a laundry room where the HVAC interior unit is- which, if you’re working on it, is nice ’cause it’s in conditioned space. But it seems there’s no access from under the house to the space under where the unit is, so I gotta figure out how to pull this cable into that room.

I trace the old cable, but it does something nuts. It goes up the wall on the opposite side of the room into the attic and down back to the air handler. I bought 50 feet of cable after measuring the run- thought I’d need 40 feet, but I don’t have enough to do that run. Also, pulling a cable through a full-height wall sucks.

So I start scuttlin’ back to the hatch to see what I can see from above.

And as I near the hatch-

I CATCH SOME MOTION BEHIND ME.

Somethin’ big just jumped up from the floor to the top of the duct. Stalking me.

I get out and figure out I can pull the cable through where the condensate drain runs. Get the fish tape down through there and, I think, into the crawl space. So I go back down to pull the cable with the fish tape and-

Find my stalker.

A FUCKING CAT.

Who also, presumably, butt-slammed some cable of the ancients and caused my current dead-short-problem.

I try to boop it off the top of the duct with one of those zip ties that Homeland Security and HVAC installers both use, but it’s not budging. So I go about my business. Connect the cable to the fish tape, then go up and finish pulling the cable to the air handler.

The house is now 55°F.

But there’s still the mummy cable to decipher. There’s no mummy cable in the air handler, so some asshole spliced it somewhere. And none of the wires in the air handler are labeled.

Mummy wire is a critical wire- it’s the reversing valve control wire. Tells the heat pump if it should make heat or cold, which we need heat right now.

I go digging around in the attic and find the mummy wire spliced into some 18/8, but WHICH 18/8 is it in the air handler? There are four.

I check continuity on yellow-black on one of the 18/8s and get nothing. Then I go back in the attic and strip and twist the yellow-black together next to the mummy wire. Recheck the continuity downstairs and it’s now continuous on yellow-black.

I have found my reversing valve wire.

Then I can rewire and label the mess the previous monster left. Only half of the wires pictured.

I get everything reconnected, power on, testing voltages at the thermostat before I connect it and I get NOTHING on red-blue/C wires, which should be ~24V.

Turns out I over-twisted and work-hardened a red wire till it broke. Stripped and twisted that back on. And finally: ~24V red-blue/C.

Then the thermostat.

And the fuse did not pop.

And we have heat.

And I’m covered in disgusting cat fur from rolling around under the house for half the day.