Can a new thermostat cause a relay to stick?

I added a new honeywell digital programmable wifi thermostat to my rheem ac system and the fan will not shut off. I wired it up to specs on electrical diagram on the unit. After running all night I faound out the compressor was not on. I took cover off of comp and the capacitor was good so I tapped on the relay heard it click turbed on power and it ran. It is stuck again, my question is is this coincidence or did the new tstat do something? It all worked fine before I added the new tstat. I did have to hook up common wire in the handler but I did it to specs, coul it have caused a short that caused the switch to blow? Thanks for the help. I know I need to replace relay but I want to make sure that the tstat isnt the issue befire I replace it.

4 Answers

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  • 7 years ago
    Best Answer

    I would say it's a coincidence. I've never seen a thermostat cause a relay to stick. If the thermostat was the problem tapping the relay wouldn't do anything.

    Source(s): HVAC contractor
  • 7 years ago

    I'm with Scott on this one. The other guy is just an idiot. You never, ever, EVER spray WD-40 anywhere on a contactor. Nor do you replace a capacitor that is running a fan just fine.

    OK, that said: the contactor relay may have just gotten a little off kilter.... If the unit has some years on it, contactors are not that expensive, and after all, it is an electro-mechanical device that can and does get wear & tear on it.

    Go ahead and put a new relay on it and do make sure the call from the thermostat is a full 24vac. If its not, simply make sure all the low voltage connections are tight then make sure all the high voltage connections are tight. Be very very VERY careful doing that....

    Source(s): HVAC tech
  • 7 years ago

    thing to do is check voltage to ac unit,need to have 24 volts.If voltage checks out fine then it is possilbe

    your relay is contacts are dirty or pitted.spray w/d 40 type oil on contacts.It also sound like your capacitor for the compressor is bad,fan only operates when relay closes.

    Source(s): hvac tech
  • 7 years ago

    unhook the common, wire

    Source(s): maint man
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