Check out some similar questions!

ALeGatorAL · Mar 18, 2009, 01:45 PM

Hi,

Thanks for taking your time to read this post. A while back I asked the question about disconnecting the Heating part of the unit and if I could get the AC to run correctly without it being hooked up. I thought I had the answer but apparently I'm still doing something Incorrect. I disconnected the white wire and shut off the gas to the furnace. The Heat limit switch is damaged and appears to be in an open position. I'm not totally sure exactly what the function of the switch is but can I run the AC without one in there if the two wires connecting it are jumpered? If I jump the two wires ( Red & Brown ) the Blower never shuts off. Any help in this matter would be greatly appreciated!

Thanks Again In Advance,

AL

KC13 · Mar 18, 2009, 01:51 PM

As long as you are not using the unit for heating, the limit control serves no purpose. Try this: locate and remove the fusible link from the limit circuit (if still present). It will resemble a small resistor in a sleeve, attached to one of the limit wires.

ALeGatorAL · Mar 18, 2009, 06:28 PM

Hi KC,

Thanks for your time. My original problem occurred during the winter with the blower never shutting off in the heat mode. My regular maintenance guy took the fusible link out at that time and everything seemed to work fine till the tenant mentioned that the AC fan didn't work and not only that, she thought she smelled something burning. She was right because when I got there I noticed the wires burnt and when I turned on the heater the flames started to back up into the closet area. I'm guessing the maintenance guy should have never cut that link out and that the original problem was the overheat switch all along. Of course he's telling me now that the unit heat exchange has a hole in it so I'm guessing it does. Anyway back to the problem at hand. When I tie the wires together the blower never shuts off. When the wires are not tied together, the compressor runs and the blower don't. What controls the blower in the AC Mode? Can that be the problem?

Sorry to be so long winded!

Thanks Again
AL

KC13 · Mar 18, 2009, 06:51 PM

I remember this problem from a while back... the blower is controlled by the circuit board, and the low voltage control circuit (indoor) is dependent on the continuity of the limit circuit. If the outdoor unit operates with the limit circuit open, it suggests that some other bypass wiring has been performed on the system, or it is a two transformer system. What wires were "burned"? Does the thermostat have separate "Rc" and "Rh" connections? P.S. What happened to cornerstonehvac? We argued about this problem, my analysis prevailed, and he disappeared...

ALeGatorAL · Mar 18, 2009, 07:43 PM

The two wires that were burnt are the red and brown wires that were connected to the limit switch. I'm not at the apartment tonight so I can't answer the question about the thermostat, sorry. The outdoor unit don't work with the wires, brown & red, not twisted together. It only works when they are tied together but the blower never shuts off. I don't know what happened to Corner, I'm sure he didn't take it personal, I use to work on Helicopters and jets but this house wiring and ac stuff has got me hoodwinked! LOL I would think that if the overheat switch has to be closed to get the fan to run so twisting the two wires that were connected to it should do the same thing, right? It just seems like something else must be controlling the fan in the AC mode and I can't make it out from the diagram on the unit. I will head back to the apartment in the morning to look at the thermostat wiring. Thanks again... AL

KC13 · Mar 19, 2009, 03:57 AM

Next chance you get, inspect the circuit board for evidence of moisture exposure, oxide bridging of printed circuit paths, and/or burning. Make sure the blower leads are wired into the board correctly.

ALeGatorAL · Mar 19, 2009, 08:06 PM

Hey KC,

Great news! The system is up and running. Seems like my maintenance guy, when he was out there the last time, was messing with the wires from the thermostat and put the Green wire on the Gh terminal instead of the Gc terminal! Anyway, I jumpered the Heat Limit Switch and relocated the green wire and everything seems to be OK! Thank You again for your help in this matter and trying to talk me through a difficult problem, especially when you're not there to see what's actually going on for yourself and got an amateur trying to relay the info to you!

AL