Posted: 3/23/2008 5:56:15 PM EDT
Our distant friend Mr. Murphy came by to visit on one of the coldest spring weekends this year.  Not to mention that it is Easter wknd too.Here's the situation: Woke up Friday morning to a chilly house. My wife was able to get the heat to run in 'EMHT' mode for a few hours and then there was no power to the thermostat and the unit would not kick on. I have a contractor friend that opened the inside unit (heat pump?) and found a 5 amp fuse blown. I changed that out and got power to the thermostat but the outside unit will not kick on. Sat: Power to thermostat off again. Panel off--blown 5 amp fuse. Is it possible that the fuses to the outside units are in need of replacement? I really like to save a ~ $75 dollar service charge for replacing a fuse myself. |
|
Something in the 24 volt side is blowing the fuse. Most likely all the contactors are 24 volts. Try disconnecting the 2 wires that run to the outdoor unit, then replace the fuse most likely an auto type fuse either the spade ones or glass bulb 3-5 amp. Then run it in EMHT and see what happens. If its good the contactor for the compresser outside is junk |
|
Something on the 24V side is shorting out. I'd check the 24V wiring at the thermostat, blower, and outside unit. See if it happens when its only in one mode. If your thermostat has a common wire (usually black) make sure its not touching the hot wire (usually red). |
|
Alright. I changed out the fuses (30amp) at the outside unit box. I replaced another blown 5 amp fuse in the inside unit. I now have power to the thermostat and can run the blower in 'EMHT' mode. The outside unit still will not kick on. Is it time to make a service call? |
Yes.... Either the contactor(s) in the outside unit are smoked or the compressor is. My bet would be the contactor. I'm an electrician, btw. Wired many an HVAC system. "EMHT" mode, incidentally, is straight electric coil (emergency) heat. The outside unit does absolutely nothing in this setting. The electric heat coils this setting energizes will be in a duct or on the air handler plenum. Considering the 5 amp fuse in the INside unit is blowing, I'd almost definitely say it's the outdoor unit contactor, because the air handler transformer supplies power TO close that contactor. It's probably fried. Seen it tons of times. They don't last forever. Nothing unusual there, just inconvenient and annoying as hell. Hope maybe this helps some... JB |
Yeah you need to call someone out. Similar thing was happening to me. Ended up having something blow up in my compressor circuit. Basically a 200 dollar fix to replace the bad part. |