I have a Rheem Furnace Model # RGPH-07EAMGR Serial # FD5D307F16000271. The unit keeps blowing the 3 amp fuse on the ciruit board. I verified the amp draw from the blower motor and it is well below the...
Hi, this fuse is for your 24volt controls, which means anything that runs on or is controlled by 24 volts. Check the thermostat wires at the board where they come in, as I have seen them skin the insulation and ground out blowing this fuse. The contactor coil on the outdoor unit is 24 volts and may be shorted. Its a matter of looking at all of the low voltage wires to the indoor and out door unit. If you have a dog, I have seen where they chew the wires causing a short, or from the sun causing the insulation to come off and short.Something is for sure causing a dead short on the control side, It would not be the stat unless you have been into the wiring behind it and maybe the R, red is touching. (9 times out of 10, a low voltage wire is touching metal or another wire, common. If all of the wires look good, you will need to do the process of elimination. Go to the outdoor unit, and the wires coming outside from indoors, if its a gas furnace, you will have 2 wires. Take them loose, and this will take it out of the circuit. Now try another fuse. If it holds, your problem will be in the outdoor unit. It would have to be the contactor coil. It has 2 small wires, one on each side. Pull them off, tape them so they dont touch and wire the 2 wires coming out back up. When you restore power to the outdoor unit, if it holds you will know its the contactor, it has points on it and this is what closes to start the fan and compressor, just 24 volt coil. This is not a high voltage problem, only a low voltage, so checking the amp draw on motors are wasting your time. After you eliminate the outdoor unit, take each wire off of the terminal block at the indoor unit. Write down how they go back!! This eliminates the stat wire and thermostat. If the fuse holds, you problem is in the stat wire touching in the wall, or at the stat. Most contractors will have an extra wire that can be used. You will need to ohm out the wires to see which is touching. Last thing to do, is kill all power, and remove the 4 screws on the board. It will have stand off's on it to keep the back from touching metal. Look at the back to see if it is burned any where on the raceways. If so, you have a shorted board. Please follow all of my steps and you will find this short. It is really very easy, now that you know its the low voltage side blowing the 5 amp plug in fuse. Process of eliminated the parts like the outdoor unit, thermostat by taking off the wires at the indoor unit and so on. You will find it. Please let me know and rate me on my help to you.
A/C, & Heating Contractor & Tech.
Jun 14, 2011 |
Heating & Cooling