Coleman/Nordyne blower problem

[myangel]

The pilot is lit and the furnace will run normal. Then sometimes, now it has become quite frequent, it sounds like the blower is starting up and then quits after bout 5 seconds, the burner is not lit when this happens. This repeats sometimes for 30 minutes or longer. Is there something inside the unit that tells the blower when to come on and go off? if so can it be bad? or what part do we need to get to fix it?
We had a htg/ac man come and put a new orifice and thermocouple on. We purchased a fan switch from you and put it on.
1992 mobile home, Coleman/Nordyne furnace is mod #7970C856
It is just my mom and I here, and we are on limited income. Your help is very much appreciated. I made several calls to try to get help, but because we aren't the contractor they won't help me. We live 50 miles outside of large city and it costs a fortune to have one of them come out here. Thank you for your help! Melisa

[Robert]

Hi Melisa,

When did you replace the Fan Switch ? That controls the blower when the heating chamber reaches a certain temp, fan switch closes to bring on motor.




Thanks,
Robert

[myangel]

I put the switch on 11-30-07.

[myangel]

The burner is not lit when the fan comes on for about 5 seconds. Just the pilot is lit.
When the furnace is lit, the fan will come on and run.

[Robert]

Make sure ducts are clear and not blocked (remove floor registers, place flashlight in one and hold mirror down in next looking back at light). Do this on all registers to inspect ducts.


If you have a/c, make sure the A-Coil is clean and clear.


Furnace may need cleaning.


Could be a faulty fan switch, but more likely that the heat is not being dispersed thoroughly and the residual heat keeps fan coming back on until it is cooled down enough.


In the top toolbar, go to HVAC link, then go to Articles link for helpful info on some of this.



Take care and best wishes,
Robert