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TechmanTechman Member Posts: 2,144
Check the voltage of the low volt circuit.Not at the stat,though!At the compressor contactor coil with the system running.Also,check the volts at the contactor coil at startup of cooling.


  • Jim RobbinsJim Robbins Member Posts: 4

    I have installed three Hunter 42999 thermostats. Each of these do the same thing as the original thermostat I replaced. Here is the problem. First let me say that anytime I connect the red and yellow wire together the compressor starts up without any hesitation. This tells me the unit is working fine. The problem is the thermostat will work anywhere from one to twenty-four hours; cycling like it should. But without external cause the thermostat will not kick back on. In order to get it to kick back on I have to turn the temperature up to say 80, wait five minutes for the compression release, then set the temperature back to 74. Most of the time the compressor will start, but sometimes it will not. It is at that point where I connect the yellow and red wire and the compressor starts right up. This tells me the thermostat is defective, but I replaced it three times. Sometimes the fan will start, but not the compressor. It is a really weird mess. Thanks for any suggestions. Jim
  • Larry C_13Larry C_13 Member Posts: 94
    How many wires?


    How many wires are coming out of the wall to connect the the thermostat? Which colors go to which terminals? At the other end of the thermostat cable, which colors go to which terminals?
  • Tom HopkinsTom Hopkins Member Posts: 539

    This is from Carol. The system here has been identifying me by other names, and I haven't gotten to the bottom of how to fix it. Anyway, I'll guess that what you're running into is a built-in 5-minute delay. It might be safe to say that most thermostats these days have that for cooling. Is it that you run into the 5 minute delay when it's been less than 5 minutes since the last cooling cycle finished, but no delay when it's been longer than that?

    I'll bet it's not a defective stat. If you have a reason for not wanting the delay, there are thermostats that you can adjust not to have it, but may cost more than the one you have. Hunter is known for being low end cost.
  • Jim RobbinsJim Robbins Member Posts: 4

    The wires are the standard R, Y, W, & G. I now they are hooked up right, because when I touch the Y & R wire the compressor takes off every time. I have considered the 5- minute delay and, like i said the unit works well except when it shuts off after a cooling cycle. After that it may or may not connect. When that happens I set the temperature to 80 and listen for the thermostat to kick off. When it does I wait 5 or 10 minutes before I reset it to 74. At that time it unusually will start when the thermostat kicks in. I called Hunter Fans and all they could say was maybe my unit was not compatible with their thermostat. I have installed a different brand and it appears to be working, however the Hunter worked for over a day before it stated to mess up. I will wait and see. I will contact you later with the results of time. Thanks again JIM
  • Jim RobbinsJim Robbins Member Posts: 4
    At a loss who can figure this one out

    This is indeed a unique problem. I install a different brand thermostat and just like the old one it worked fine for a few hours and then it too started to do the same thing. I am at a loss. Again; why would a thermostat work perfect for several hours and then stop kicking on? I have set all the programmable setting to be at the same temperature of 74. The electric has been stable, no outings. "What we have here is a failure to communicate." BUT WHY?
  • Larry C_13Larry C_13 Member Posts: 94
    Step back to the begining.


    May I suggest that you stop, take a deep breath, and start all over. Forget that you "know" that the thermostats are bad. Perhaps something has changed at the furnace end and now the furnace controls are smoking the thermostats by creating conditions that are outside of the thermostats operating range.

    That is why I asked what wires are connected to what terminals at both ends of the thermostat cable. It is possible that a jumper at the furnace end came off, or a jumper has formed by a wire strand shorting to an adjacent terminal, or perhaps someone accidentally drove a nail or screw into the thermostat cable, or waved a torch in the vicinity of the cable and melted two wires together. Weirder things have happened.

    Do you still have the previous thermostats? Can you open them up and see any indications of damage? Things like overheated connections, burn't traces on circuit boards, things that don't look right.

    Do you rember what happened immediately before you noticed the original problem? Was someone working on the furnace, air conditioner, the condensor, moving furniture, hanging pictures, unclogging drains, etc. Was the thermostat ever relocated from its original location. Perhaps a hidden splice in a wall opened up and the current is now running thru a cross connection in the thermostat?

    Did someone steal power from the furnace to power up the doorbell? Did someone install or disconnect a humidifier? Added insulation to ductwork? All sort of possabilities exist where a new connection was made or an existing connection was broken.

    If nothing can be found, try running new wire from the furnace to the thermostat and see if that fixes the problem.

    Good Luck,

    Larry C
  • Change the batteries?

    If they are battery operated the ones shipped with the stats are usually junk. Put some fresh Energizers in there and see if that doesn't solve the problem.
  • Jim RobbinsJim Robbins Member Posts: 4

    Hello Larry, thank you for taking the time to help me. After reading your suggestions I remember it was raining and lighting close to the time the problem came about. I think we are getting closer to the answer however, because this am the compressor started to act different. It will now not shut off even if I pull the thermostat from the wall. The only way to stop it is to trip the breaker. That is at least a consistent problem and not an intermittent one. For the past three days the system only failed to come on twice, and it has been hot in OK. I can now look at a new approach as you told me to do. I will keep you posted as I find out what the problem was. Thanks again, Jim
  • Tom ShekitaTom Shekita Member Posts: 17

    This sounds more like a contactor issue
This discussion has been closed.


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