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Air Conditioner malfunction

Central Heat (Gas) and Air system is blowing 3 amp fuses on control board. Unit specs follow: Carrier Product 58GP-050---111EA Model 58GP050-EA Serial # 2791A02092 Have replaced fuse, checked Ckt Brkrs and other fuses, manualy engaged compressor relay (outside), searched for any frayed or loose wires, replaced thermostat, bypassed Hi/Lo limit switches. Blower runs continuously, even with unit set to "OFF". Any Ideas????

Posted by Papdaddy on

  • 4 more comments 
  • Papdaddy Sep 23, 2007

    Thanks for your input...had already tried some of what you suggested but will follow up with some more of your ideas...I have replaced the circuit board once before (last Winter) but it may be on the fritz yet again...was trying to see if there was something else to try before I sank another $100.00 into a board only to find it wasn't the problem. This board has the relays that can't be replaced individualy, the whole board gets it. I'll get back to it and let you know...Papdaddy

  • Papdaddy Sep 23, 2007

    Thanks for your latest comments/ in the process of troubleshooting as advised... will let you know what happens...


  • Papdaddy Sep 24, 2007

    here is the latest... going by your earlier suggestions, I checked continuity on thermostat wires and all checked out ok both seperately and together. I then started jumping from the red wire to the other components. red to green caused my fan to to white caused the heat mode to try and start (gas is off at moment - summer) all was fine until I jumped red to yellow (Conderser unit?)...pow...blown fuse and now fan runs continuously would seem that this is where the problem I've got to try to figure what is wrong from here...


  • Papdaddy Sep 24, 2007

    Thanks for the added info...I'll try it as soon as my schrdule permits...thanks again for all your help so far...


  • Papdaddy Sep 25, 2007

    We now have A/C!!! Went and re-checked the outside unit for "weed eater damage" and indeed found some. The damage was right at the wall where the copper pipes and wiring came out of the house. I had to surgically remove some of the mortar in order to find, and repair, the actual damage to the insulation The both wires were right against the pipe and the yellow wire had a small break in the insulation. Thank you so very much for your help and very knowledgable advice.


  • Anonymous Mar 12, 2014

    The red LED light that blinks if there is a fault on the unit is not on. I can engage the contact with a screw driver and the blower starts, but the heat pump will not engage. Is this a thermostat issue?



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Hi, Sounds like you have a short in the control circuit to me. Turn off all power going to the unit. Write down or otherwise mark the wires leaving the control board going to the thermostat. Remove them from the control board. Replace the fuse. Turn power back on and see if the fan still runs. If it does, check and or replace the heat limit switch that brings the fan on during the heat cycle. It may just need adjusted. If the fuse blows, I would think that the control board is probably bad. If it doesn't blow, Remove the thermostat. Leaving all thermostat wires open check them with an Ohm meter. There should be no continuity between them. Twist all the wires together at one end and ohm them again at the other end. You should have complete continuity on all wires. If the wiring checks out, down power the unit. Double check your wire colors and rewire the control board. With all wires open at the thermostat, turn the power back on. Touch the RED wire to the YELLOW wire. The Condensing unit should come on. Touch the RED wire to the GREEN wire. The fan should come on. Touch the RED wire to the WHITE wire. The heat should come on. Down power the unit. Replace the thermostat. Test unit. If the fuse has lasted ok but blows now it is either wired wrong at the Thermostat or the thermostat is bad. I hope I have helped. NOTE: If you can not understand these instructions. Call a licensed Heating / Air conditioning company. kstfas

Posted on Sep 23, 2007

  • 1 more comment 
  • Anonymous Sep 23, 2007

    Good to hear from you. Yes, please keep in touch and let me know how it works out. If the board is the problem again I would contact Carrier and let them know that its a continuing problem. You may have to go through an AC company to do that. They may have another solution to keep it from happening again.

  • Anonymous Sep 24, 2007

    Ohm the two control voltage wires to the condensing unit the same way but also check them to ground. (the copper pipe) There should ne no continuity to ground. Check for weed eater damage. Most condensing units control circuits are powered by the inside transformer and need a neutral from the inside transformer and a HOT supplied from the yellow wire from the thermostat. The neutral for the circuit will also have the fan relay and gas valve neutral side connected to it. There will be control voltage between it and the RED thermostat wire. Probably 24 VAC. This is where one wire to the condensing unit will go. The other one needs to go to the yellow wire from the thermostat. Note: These two sets of wires do not need to go to the circuit board and can just be twisted together and wire nuted or taped. Make sure there are no shorts or grounds before doing this though or you may burn a transformer.
    Hope this helps.

  • Anonymous Sep 25, 2007

    Its people like you that keep me answering questions on here. Glad I could help. Send me a note sometime it you would like.
    [email protected]




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Posted on Mar 20, 2008


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