Gas and Oil Home Heating Furnaces - short cycling Intertherm

I have an Intertherm gas furnace. The problem is this: The burner ignites, then a couple of minutes later the blower starts running. Everything is fine for a couple of minutes and then the blower shuts down! Couple of minute later it all starts up again, then same thing happens. I have changed the fan and limit switch but no imrovement. Any suggestions?

Filter clean? Same tstat?;) ED

I tried other t-stats and the filter is clean. It just seems to heat up and you can hear the limit switch click and then the fan will run for a minute or so. Limit switch clicks,fan shuts down.

How old isthis furnace? Dont sound right limit switch clicks fan shuts down.Fan should run limit should only turn burner off?????You coud turn power off put a jumper on the limit control and see what you have that way. STAY with the furnace till you take the jumper off the limit;) ED

Ed, the furnace is an '85 model. The limit switch is a combo fan and limit switch, their are 3 prongs on the outside, and 2 disks that are in the heat exchanger. If it gets up to heat for what the tstat is set on it will turn the burner off as it should. But if it short cycles before hitting that set point it keeps the burner running till it gets hot enough to start again.

I just got back frim looking at the furnace again, I jumpered from the hot terminal over to the fan terminal when it shut down and the fan started up again and ran until I removed the jumper. Would this mean that the new limit switch is bad?
Thanks.