Intertherm Gas Furnace. Blower coming on intermittently

[Guest]

I have an Intertherm "HeatRite" Gas Furnace Model # MGH-055-ABWL-06. This is the original one and the MH is a 1988 model. I am having the following problem. Here's what happens

t-stat switched to heat
t-stat turned on, Burner lites, Blower comes on a minute later
Blows warm air and heats the MH
T-stat kicks off, Burner goes off and after cool down blower goes off

Everthing seems to be OK up this point. Here where the problem starts. After 5-7 minutes the blower kicks back on just long enough to get to about full RPM and then kicks back off agian. Now the blower will continue this on and off thing every minute or so. The only way to stop it is to turn off the main breaker to the furnace.

About 3 weeks ago I had a Tech come out and change the thermcouple on it. It was working fine until now. The only thing I noticed now is that it seems like the pilot is ajusted a bit high. This is the only work that has been done to it. Thanks

Dave

[hvac1000]

Sounds like the combination fan and limit control.

NOTE: this control controls the operation of the fan depending upon how much heat is in the furnace. It turns the fan off or on depending upon the furnace temp. More than likely yours is out of calibration BUT I would check the following before ordering.
Make sure the return air and filter is open and clean. Make sure that no registers (discharge air ducts) are closed off in the home.


Order on this page

If yours looks like the picture on the below link page here is the part number. 626235


http://www.mobilehomerepair.com/NordyneGas.html

Left side mid way down.

Have a nice Thanksgiving.

[Guest]

Thanks, I'll check the filter and registers to make sure everything is OK there. This is one of my rental units so I'll have to go out and check and see which fan and limit control switch is in the unit.

Thanks very much

Dave

[Guest]

I checked my unit and the fan & limit control switch is part # 6262920 I will be ordering one. I made sure all the registers were open in the MH. Also, the only filter for this system in one that you place in the front cover of the furnace so I made sure it was clean.

Just curious, Can the pilot be ajusted too high causing it to be too hot when the burner IS NOT lit?

Thanks,

Dave

[hvac1000]

You would have to have one huge pilot to cause the blower to come on like in your description.

In fact I do not think you can get a pilot large enough to effect the blower control.

Have a great Thanksgiving.

[Guest]

I received the fan & limit control switch and replaced it. I still have the same basic problem. The only difference I have noted is that the blower now kicks on about every 5 minutes instead of every minute or so after the initial heat cycle. There is also a blower relay in the circuit. Could this be causing a problem? Thanks.

Dave

[hvac1000]

The problem is residual heat. Usually there is enough differential in the control to stop this from happening.

Something would have to kick on the blowwer relay for it to be a problem.

Are you sure all the ducts are open and the filter and return air are not blocked in any way?

[rhaines751]

Thats funny I own a 1988 mh and have the same furnace and its doing the same thing . I was thinking it was geting to hot or some thing but i dont know I just got this place . Did you find out what was doing this ? Maybee the same thing with mine lol

[Robert]

Hi,

Please read all replies and try on your problem. If it does not help, then come back and start a new thread with problem and furnace info.


Thanks,
Robert