That one Monday where everything went sideways on a simple thermostat swap

I had a basic Honeywell thermostat swap booked for 9am last Thursday. Easy money, right? Got there, old unit came off fine, but the new one's wiring labels didn't match anything on the old plate. Spent 45 minutes tracing wires back to the air handler in a dusty crawlspace with a bad flashlight. Then the homeowner's cat knocked my screwdriver into a floor vent. Has anyone else had a 'simple' job turn into a three hour nightmare over something stupid like mismatched C-wires?

4 comments

4 Comments

danielnelson22d ago

...ended up in almost the exact same spot last year, that moment where you're staring at a blank wall and the new thermostat's letters don't match anything. What finally worked for me was taking a picture of the old wiring before I even touched it, then I used a multimeter to check for voltage at the air handler side. Turned out the previous guy had used totally different color codes, but the C wire was actually just a spare blue wire tucked back in the bundle. After that I started keeping a little label maker in my bag for jobs like this, saves a ton of headache when the labels don't line up.

riley_wood8422d ago

The label maker thing feels a little extra for a thermostat swap, doesn't it? Like you're prepping for open heart surgery when it's just a couple wires.

ruby_henderson3622d agoMost Upvoted

The label maker does seem like overkill until you're the one chasing phantom wires at 9pm. I've definitely been there with a sharpie and a piece of masking tape that fell off halfway through the job. @laura_schmidt82 is right about manufacturers ignoring color codes, it's like they all picked their own rainbow on purpose. My label maker story involves labeling the kitchen cabinets for a dumb organizer thing and then having to admit I used it on a thermostat too. Not my finest moment but the wires were actually right that time. Nothing wrong with being careful even if it looks a little extra, we've all made that mistake once.

laura_schmidt8222d ago

I've done the same thing with taking pictures first, @danielnelson, and it saved me when I found the old thermostat had a jumper between R and Rc that I almost missed. Now I always wonder why thermostat makers can't just agree on one color code.