It's Not the Computer's Fault This Time

This September has started out a little bit warmer than usual for this part of the country. On Saturday my air conditioning went out. I didn't think it would be much of a problem because it is almost time to turn off the costly device. Saturday was pretty warm and I was glad to open the windows at night. Sunday was not much better and so I called the repairman on Monday morning.

My heating and air conditioning unit is 15-years old and so it is not surprising it is starting to show its age. In the past several years, I have had to replace the furnace controller twice. The controller is a very simple computer that controls everything about the heating and cooling of my home. Since it had gone out twice already in about the same number of years, I figured it needed replacing again. I looked on the Internet and a new one was going to cost me $200. You can get one of those new NetBooks for $200 and so I was hoping the repair would fall under the warranty.

The repairman came out and I recognized him from when he was out less than a year ago. I told him that if I leave the AC off but try to run just the circulating fan, it runs for a little over two minutes and then shuts off. The same thing happens with the AC on. That eliminates the problem with the air conditioning unit (good thing because those are really expensive). He agreed with me and so he started his diagnosis at the fan unit.

When I am working I hate it when someone is standing over my shoulder watching and so I headed into my study to get some of my own work done. My study is in the basement right next to the heating and air conditioning unit and so I could still hear the repairman working. I was surprised when he turned on the heat. Its a million degrees outside and this crazy guy turns on my heat. My hope was that he could get the AC fixed shortly or I wasn't going to need to turn on the stove to cook food in my kitchen.

The heat ran for about 5 minutes when the repairman turned it off. So that leads one to the question as to why the fan can only run for two minutes alone or with the AC but can run longer with the heat. To me it sounds like a stupid computer problem and I would have replaced the controller and gone on to my next appointment. However that didn't fit with the repairman's experience and he continued looking for other sources of the problem. In the end it turned out to be a faulty switch.

On the outside of the fan unit is a switch that is the same type used to turn on and off lights throughout my house. The electrician that wired up the furnace never had a clean contact for one of the wires attached to the switch and it was wiggling around loose. The vibrations from the fan would wiggle it loose causing the fan to shut off. Running the heat caused the connections to expand and increased the contact area so the switch would work perfectly. Furthermore it was probably the faulty wiring in the switch that caused the computer to fail the past two times.

In the end it turned out to be a $2 switch and not the over-priced-heating-and-air-conditioning computer. Those of us that work around computers know that they can be the cause of a lot of problems. That wasn't the case this time and now I know I need to be a bit more thorough the next time I blindly assume it is the computer's fault.