Homeowner calls and explains that there is no heat, the air was working fine until we switched over to heat when it got a little cool this fall. We collect as much information as the homeowner can provide before we begin our repairs.
1. We had problems recently and the Service Company installed a new Thermostat.
2. Heat has never been used since then.
3. When we called for heat, nothing works at all now.
The first thing we noticed was exposed wiring at the air conditioner thermostat wires. These were addressed one of the very first things. The weather had deteriorated the insulation on these wires and it was very possible that they had contact with each other so we clipped each wire and eliminated problem areas.
Then after checking the proper voltage in, we began to look at all components and wiring. Looking for any obvious burnt or broken wires or any thing at all that does not look right.
In this case we looked at the wiring on the thermostat one of the very first things. All wires were color coded and seemed to be in the right place and we began to dig deeper.
In the air handler we as stated above inspected for obvious problems. The 24 volt output fuse was hidden under some wiring and it was open or should I say blown. Okay so our immediate thinking is all we have to do is replace this 50 cent fuse and all will work fine. Well you guessed it. NOT
This was only the beginning of a three day affair. It was discovered that between the air handler and the thermostat there was a clump of wires that had been connected with wire nuts. So we clipped away and checked for shorts back to the thermostat. The wiring seemed fine so we rewired properly and proceeded. Back to the air handler and we disconnected the second thermostat wire out to the air conditioner to isolate the heat form the air. At this point we would check each leg of wire and all components and add new fuse and call for heat and these fuses are beginning to add up. Of course this is not the right way to do this testing, however we wanted to protect the 24 volt transformer and this was the only way we could insure protection here.
Long story short we discovered a weak contactor that was replaced with a spare we had on the truck. It was also discovered that there was a hairline crack in on leg of the bladed contact point on one heat strip. Of course the thinking was that this might be a possibility of why this fuse is still blowing. After cleaning up and soldering the hairline crack, we called for heat again. POP the fuse blows again. This is near a giving up point. Then it came to me that well there is no reversing valve on the air conditioner so I’ll just eliminate the orange wire on the thermostat and the unit as it is not necessary. Pop yes you guessed it.
I hate to be whipped in situations like this. I called in an Electrical Teacher form a local Technical College. After he went thru a couple hours of the same testing that I had already been thru, it was determined that we had a bad thermostat. Remember we had info that there was a new thermostat installed recently. So with this info we went to supply house and picked up new thermostat and back to make the final repair.
Installed new thermostat and called for heat and “POP”.
Now this is personal. Rechecked the thermostat wire a second time. clipped and basically looking for a needle in a haystack. Isolated the heat from the air again and this time we installed the thermostat and called for heat. Checked the wiring at the air handler with meter and was sure that what we would or should find is three wires that were activated with thermostat.
1. red 24 volt supply
This should be all it takes to make the air handler operate in heat.
Well the blue wire was also called by thermostat and this is where all the problem with the fuse wound up being. Because blue is the common on this unit in the low voltage supply it was overlooked as necessary at the thermostat.
We removed the blue wire from thermostat, hooked everything back up and called for heat and after four days of troubleshooting the thermostat and heat got along together.
Still a small problem now with the air conditioner, fan works but compressor does not. The blue wire was necessary to the unit outside to complete the 24 volt low voltage circuit that pulls in the contactor.
So after much discovery and relentless determination to get this family some heat we have this system operational and some much needed maintenance that was taken care of in the discovery of the fault.
Also it should be noted that there was inadequate wiring diagrams onsite. Even the internet was very vague and we were unable to find the problem with diagrams that we had found.
Problem: 24 volt low voltage output fuse keeps blowing.
Solution: Removed blue wire from thermostat.