Air conditioner wet switch

Anyone have any experience with a little device called a wet switch? It apparently detects water on floor on the a/c air handler and shuts off the system if wet.

1 Like

I used something similar in crawls.did the same. Encapsulation of crawls needed them or they would fill with water. They do work.

I had one for the first time the other day. Never seen one before. Picked it up and set it back down on a wet spot on the slab under the air handler. Didn’t know it shut off the a/c. Now I’m having to pay for an HVAC service call. Live and learn!

1 Like

Scott, isn’t that the truth…Live and learn!

If wired correctly they work great. If they get wet they have to dry completely or the switch will stay open. It’s best to have wired to break the 24 volts to the condenser and not the complete system. Reason to wire them that way is to allow the blower motor to run in case the system is freezing up (Melt the Ice). I have seen them open due to damp conditions in basements or crawl spaces. I hope this helps.

Why are you paying for a HVAC contractor. You did the right thing. You placed the wet switch on the perfect location informing the client there was an issue. If you reported condensate under the plenum I would dispute they claim.

From Wet Switch.
A solid state control designed to help prevent flooding, damage to carpets, walls, furniture, ceilings, etc. Now has a built-in test and reset button for easier installation. Turns system off when detecting moisture due to condensate or drain leaks.

Robert, you make a good case. I agree. But I don’t know if it’s worth arguing with the agent or homeowner. I may win, but lose in the long run.

Thanks Eric for that explanation. That explains why I never heard the fan shut-off. It must have stayed on while the outside unit shut down. I never knew there was a problem till the agent called me a few hours later.

Where exactly did you move it from and to, and why? Something doesn’t add up.

My thought was why move things around in an inspection that is visual?

You’re right. That was mistake number one.

1 Like

Sensor was on the floor in the corner that was dry. I moved it toward the center where some water was pooling. Not a smart move on my part.

Why was there water pooling on the floor? What was the source?

I already had in my report to contact an HVAC man. When he came to reset the wet switch sensor, he also repaired the leak (supposedly from the condensate drain line).

Although, obviously, you should not have repositioned the sensor… the fact that there was a leak… would have caused bigger flood and the sensor would have tripped eventually. If they are trying to blame you for the HVAC service call it is very unprofessional of them. In fact, it sounds like you caused the issue to surface sooner and possibly prevented a bigger problem. That is how I would explain it to the parties involved and ask them how they wish to proceed. Although I mistakenly repositioned the sensor… the relocation caused the leak trigger the sensor… earlier than otherwise. Although I don’t feel accountable… I do stand behind my outstanding service and am willing to reimburse… blah blah should you feel it was my mistake the unit was leaking and required a service call… then let them decide. That’s how I would approach if I felt they are going to get nasty, etc…


I agree with you Simon and I like your wording. I’m willing to pay to reset the moisture sensor, but they better not try to stick me with the repairing of the leak that was already present.

If you already had it in your report to contact an HVAC professional, I can’t understand why you felt the need to trip the sensor by moving it to the moisture. It has a test and reset button for that purpose if you really felt the need to test the unit. If you’re not familiar with the operation of the device, you shouldn’t be manipulating it without knowing the potential outcome. Sounds like curiosity cost you some money this time, and I think it was the correct thing for you to pay for this one. I would say you should offer to pay the fee for the service call and switch, the leak is on the sellers though.

I would have simply added to my narrative that the unit was equipped with a moisture alarm or switch, however it is either not functioning or out of the path of travel of the moisture and therefore did not operate as intended. Recommend the HVAC professional evaluate the installation and location of the switch to determine whether relocation, repair, or replacement is needed.

While it sucks that this happened to you and cost you some money, step up and offer to do the right thing before being asked to do so. Agents and clients will remember this and next time they need to recommend someone, you may just get your lesson fees back…

You’re right my friend. I only picked it up to show the client during the walkthrough. Lesson learned.

Good news. Broker agent called and isn’t charging me for incident. It was so minor and no damage done. We even laughed about it. Thank you Lord—I need to keep the good relationship with him and his firm! I did screw up though and won’t do that again!


Yes, I had the experience, but it created some problems, even it detects on the wrong time. So I had to contact ac maintenance in Dubai and the fixed the problem.