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Over temp limit switch questions.

Robbie B

Well-known member
Joined
Jun 24, 2014
Messages
1,320
Location
Sunny side of hell
Spent this evening working on my hvac system. The problem I’m having is weak heat output. I got into the system and checked a couple things this evening. Had some burnt wires coming out of the 240v terminal block. Stripped the bad off them till I found good wire and hooked back up. Didn’t notice anything else bad on the power side. Evap coil, which in in front of the heat strips, was pretty raunchy so I took a wire brush and raked the crud off of it. Tested the coils 11 ohms each and the nuts on the ends are pretty rusty. Tested the temp over limit switch. Got a reading of 2 ohms. Everything I’ve read and every hvac tech video I’ve watched showed this switch having 0 ohms. Also everything says when it fails it goes full open and the fan will continuously run. Is there such a thing as half failed with these switches? I didn’t do a whole lot of test in on the main electrical box mostly due to time constraints and didn’t want to be in the panel in the dark. Anything else I should be looking for? Seemed to me the most likely culprit would’ve been bad coils but they test good.


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Bert_

Well-known member
Joined
Dec 24, 2016
Messages
9,758
Location
NW Iowa
Probably didn't have a good connection with your test leads.

Check the sequencers also, they can fail.

Check each coil with an amp meter while running.
 
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