Furnace cycles on and off too frequently

bryantyme · Tue Jan 06, 2009 12:19 am

Intertherm model MGHA-090ABPQ-01

I keep my thermostat about 50 degrees during winter when I am not at my second home. When I arrive I turn up the thermostat and the furnace cycles on and off frequently until reaching its desired temp. I was thinking this is because it is sucking cold air into the burner and bringing down the internal temperature, therefore shutting down the blower till the temperature comes back up. Is this true? Is it OK? Can any of the limit switches or fan switches be changed to help this situation. Is this the way it is running when I am not there and it is set for 50 degrees ?
Is this OK?

Bryan

Robert · Wed Jan 07, 2009 4:39 am

Hi Bryan,

If it is just the blower kicking on and off, may be a bad fan switch.

Fan Switch # 626337 can be seen and ordered through PayPal

from left side of page here :

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

Also, check burner and burner orifice for blockages such as spider/web.

Thanks,
Robert

bryantyme · Wed Jan 07, 2009 3:53 pm

Thanks Robert.

I will replace the fan switch and see if that works.

Robert · Wed Jan 07, 2009 4:39 pm

Hi,

You're very welcome, happy to help.

Thanks,
Robert

bryantyme · Mon Mar 23, 2009 1:54 pm

Robert,

I replaced the fan switch and thoroughly cleaned out everything I could take apart.
I Still have the same issue.
I read somewhere else that the sensors may need to have a sheild over them.
Does this funace need a sheild over one or both of the sensors? And if so which one?

Robert · Mon Mar 23, 2009 5:09 pm

Hi,

Does your t-stat have a heat anticipator slide bar and if so, is it set correctly ?

Not sure if that model has a shield over fan switch. You can remove switch and feel around inside to see if there is one.

It would be just above the switch. Then contact Nordyne and ask them.

You could also go with an adj. fan switch and raise the cut in temp to possibly alleviate this problem.

Thanks,
Robert

bryantyme · Mon Mar 23, 2009 5:44 pm

Hi Robert,

I believe the heat anticipater slide bar is set correctly.
I have tried sliding it into other positions but have had no effect.
What is it supposed to be on?
Can you tell me what the model number would be on the adj. fan switch.

Thanks for the info,

Bry

Robert · Mon Mar 23, 2009 6:19 pm

Hi Bryan,

Look on gas valve for amp rating or in owners manual for correct setting.

Will get with Mark tomorrow and see what he has in adj. switches.

Thanks,
Robert

bryantyme · Wed Mar 25, 2009 10:30 am

Any luck finding the adj. switch?

Bry

Robert · Wed Mar 25, 2009 3:41 pm

Working on it now, we've been playing email tag.

Thanks,
Robert

Robert · Wed Mar 25, 2009 5:26 pm

Did you ever look/check to see about the shield over the fan switch ?

There should be a shield over the fan switch. Sometimes they break loose and fall off or could be the fan switch and limit switch are mounted in wrong port holes.

If broke off, can be fixed with sheet metal and screws or pop rivets.

If in wrong ports can be fixed by changing them.

If broke off, should see/feel rivets, jagged edges, etc. to show it was there and should see it down inside furnace where it landed.

Fan Switch needs to be a F125*- 40 which will cut in at 125* and cut out at 85*.

Adj. would need 125* in range with a 40* diff. cut out.

That extra 10 degrees before cut in will probably solve the issue also.

Will try to find the F125*- 40 tonight and post tomorrow.

Thanks,
Robert

bryantyme · Fri Mar 27, 2009 8:59 am

Robert

I have not been there to check it recently.
The first thing I will do is check to see if switches are in the correct ports.
When I cleaned it last I did not find a shield laying at the bottom so I'm thinking it is still in place.
I will be checking it over again April 8th.
If the switches are in the correct positions I will have to try the adj. switch that you are attempting to find for me.

Thanks

Bryan

Robert · Fri Mar 27, 2009 3:36 pm

Hi Bryan,

You can use a permanent set temp fan switch of F125*- 40 or an adj. that has 125* in the cut in range and a diff. of 40*.

That will cut the fan in at 10* higher, but still give same cut out.

Will try to get the switch soon, been ducking and running here dodging bad weather and tornadic activity.

Should be calmer after tonight for a couple to 3 days so I can get more work done.

Thanks,
Robert