Furnace overshoots set temperature

[Swimmer22]

I have a question related to a manufactured home (16x80) I purcased this spring. It is a new 2005 unit with a Miller (Nordine) hot air oil gun furnace with A/C. The problem is when the unit kicks on to heat the home, it runs too long and overshoots the desired temperature significantly. If set at 72 degrees, the furnace runs and the blower doesn't stop until the inside temperatue is around 79 degrees.
Also, once the unit stops, approximately 4 miuntes or so later, the blower kicks on again and runs for a short time (probably a minute) then shuts off. When it does this, the oil furnace is not running, just the blower.

Can anyone tell me what may be wrong with this unit. Is there some place to set or adjust the furnace so it is not overshooting the set temperature so significantly? Also, should the blower be kicking in and running a second time like it does? I hope something can be done as it goes from chilly to sauna everytime the furnace runs....... Thanks.

[Mark Bower]

You may have a couple issues. Possibly the thermostat on your wall is giving you faulty readings.

When the furnace quits heating, does the blower run for awhile. If the blower is coming back on, it's because there's still a build-up of heat inside the furnace that is tripping the fan switch.

Also post your model furnace model number.

Mark
You gotta see my repair manual!

[rmurray]

Check your home owners manual for the phone number of the furnace warranty....Sounds like a thermostat problem.....The blower comes on when the fire box is hot to cool it down as a safety feature...But the furnace should shut off at the thermostat temperature...

[Swimmer22]

Mark,

The furnace is a Miller, model number M1SB-056A-BW, with a Miller 3 ton A/C unit.

When the furnace quits heating, does the blower run for awhile?
Yes, I believe it runs for a short time but it is hard to tell over the noise of the blower running.

As you stated about the blower coming back on to release the build-up of heat in the furnace. Is this normal? Should the furnace be doing this or is this a safety hazard?

[Eugene]

I think I answered this in a different forum.
It is the accuator in the thermostat base.
It needs to be set to the furnace instructions recommmendation. probably .3
Take off the cover, and find the slidding pointer with the metal guage.
that is what is out of wack.

[fire]

I come across your furnace whrn I was looking for the same over shooting temp problem. Did you ever get to the bottum of it ?