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Genoeddie · Jan 9, 2010, 10:11 AM

It seems co-incidental but my intertherm furnace in very cold (below zero) weather, the blower fan kicks on and of for just a few seconds at a time and doesn't seem to stop doing this until I go to the wall thermostat and turn the fan to "on" instead of auto. Then it runs fine this way. After a few minute or even a few hours, I'll switch it back to "auto" and it works good for a few minutes or several hours then the fan goes back to rapidly kicking on and of again until I switch it back to "fan" on the thermostat??

twinkiedooter · Jan 9, 2010, 11:43 AM

I have an Intertherm electric furnace. What you have is a "pulse system" like mine is. When I first spent a winter with this furnace it drove me bonkers going on and off every few seconds that first year. I called Intertherm and they advised me that this was normal operating for the furnace. It was not until I had to have the furnace repaired that I was told this was a pulse system. Then everything made sense to me. I also asked the repairman if my system could be changed to one where it didn't go on and off every 2-3 seconds. No. That's the way it was manufactured to do just that. It is an energy efficient feature of the furnace.

For years my furnace would go off and on like this. It would stay on for about 3 seconds or less then off. On, then off. It would do this about 34 times for that heating cycle. I did something new this season. I bought a different filter for my furnace. Now the unit stays on to the count of 8 seconds and then off. It cycles on and off about 6-7 times per heating cycle. If anything it now works like it did when it was brand new 7 years ago. It has something to do with the unrestricted air flow into the unit I figured out using the new air filter. The other way of cycling on and off every 2 seconds drove me bonkers not being able to hear my TV or sleep properly.

hvac1000 · Jan 9, 2010, 01:19 PM

WOW that is some interesting information since I have all the Intertherm furnace and repair manuals and there is no pulse system listed. This is very interesting and I believe the issue needs to be cleared up at least for me.

Genoeddie can you post your exact model number off the label on the furnace behind the front burner area door so I can lookup your unit? If your unit is in a mobile or manufactured home please state on your next post.