We have a heating/AC unit that was installed about 20 years ago. The furnace unit is in the attic. We experience kind of an odd problem in the winter when the outside temperature is cold (below the mid-40's F). Our furnace comes on in the morning, heats up the house, then shuts off where the thermostat is set, but if it tries to come on again up to about an hour and a half after it shuts off, it won't stay on. The furnace fires up, then when the blower comes on, the furnace shuts off. Again, this only happens when it is cold outside. We have adjusted the thermostat, but it doesn't seem to help. We even replaced the thermostat. A board was replaced in the heater unit a few years ago (the old one burned out). This problem seemed to get worse after the board was replaced. We are experiencing colder than normal morning temperatures at this time, so the problem is being more evident. Once the outside temperature heats up, there is no problem.

Take a minute of you time to help us help you.

The EXACT brand and model numbers go a long way in helping us understand just what kind of equipment you are having a problem with.

The type of fuel is also important information to pass along in your post. Natural gas, Propane, Heat Pump System’s with or without an Electric furnace or Gas and Heat pump combo (Dual Fuel) and weather or not the unit is two piece (split system) with one section inside and the other outside or if it all resides outside (Package unit).

In most cases the time you spend telling us about your equipment will pay off in quicker and better answers which will better serve you.

There are many extremely talented people with a vast number of years in this industry on this board that try to help you. Please understand that since we are actually not looking at your equipment On Site we have a large handicap to try and overcome and the more information you supply us the better the diagnosis will be.

In some cases we may not be able to help at all. Extremely complex issues may have to be dealt with by a local HVAC service company since as mentioned before we are limited by the fact that we are not there to actually see and test the unit to come to a professional conclusion.

Thank you