Nest Thermostat E74 Error – Troubleshooting

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Several nights ago we arrived home from dinner and I noticed that the a/c was not working. We have a nest thermostat in our living room and I quickly noticed the Nest Thermostat E74 Error on the screen. I began googling the error and I couldn’t believe how many people were having this issue.

There were several different sites and YouTube videos showing what other people were trying to do to figure out the issue and it had nothing to do with the issue I was facing.

I pulled the nest unit off the wall and made sure all the wires were connected and tight. Then I check my fuse box just to make sure the circuit breaker didn’t trip. My next stop was the attic and I was shocked to find out that my a/c drain pan was full of water and luckily the float switch was working properly or we would have had a mess.

Why is there standing water in the drain pan?

A full drain pan means that there is a clogged drainpipe! When moisture drips off the evaporator coil, it carries dirt and particles that can build up in your A/C’s drain and cause a clog. So now what do I do?

How do I fix it?

The first thing to check is your outside drain line where it exits the house to see if there is any debris blocking the line. I didn’t see any visible debris so I grabbed my wet/dry shop vac and hooked it up to the end of my outside drain line and turned it on, and within seconds the clog was clear and the drain line was open. voilà

Keep in mind that you may need to contact your local A/C professional if the Nest Thermostat E74 Error persists after you try these steps. If you liked this article, make sure you share it to keep the word going!

Send us a message or comment below and let us know how you fixed your Nest Thermostat E74 Error below. Don’t forget to check out some of our other house hack posts.

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Author: Trey Colbert

Founder and editor of and co-owner of Flipping Hitched. I'm passionate about adventure, life, business, family and travel! My greatest and most important adventure is being a husband to an amazing wife and father to 5 creative girls and 1 adventurous boy.

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