I have a Intertherm Furnace. The gas valve comes on and it will ignite. The tempeture reaches the level for the fan to come on. The fan will start but shuts down after 30 to 45 seconds and the fan will restart again and shut off after 30 to 45 seconds this will continue until the temp in the house reaches it setting. The gas valve works fine but fan will not stay on. If I switch the termostat fan from auto to on the fan will stay on. My furnace model is M# MGBB-090-ABPQ and the Serial # is MGB 9412-07288. I have replaced the two sensors the fan limit and the themostate sensor (heat) but did not solve the problem. This furnace doen't have a circuit board controls. It is a very simple running furnace. The only thing that I could think of is that it is drawing cold air and causing the temperature to shut off the fan. Please help me. Please post no email address.

I have no information on your model number of furnace for a recall.

Parts list

http://www.generalsupplyinc.com/PDF_Catalog/InterhernmMillerGasFurnaceParts.pdf

Make sure ALL registers are open and the return air not blocked with a clean air filter.

More than likely your furnace is not firing at its designed capability. This could be caused by many different reasons. Incorrect orifice,low gas pressure, defective or not properly adjusted regulators, etc.

Since we cannot test for this in this format I suggest you contact someone local who can. You have spent money for parts you did not need and that is a shame but with the proper tools and knowledge I am sure your unit can be put right. The unit you have is a good unit and I have serviced quite a few over the years. Very trouble free if properly setup and adjusted.

Well it may work or it may not. I worked on one of these a while back it was a real pain, the owner would not leave me alone I think he wanted to date me. If I'm going to drive three hours one way I would want a young woman not and retired old man.