Furnace problem -

Turn temp to 70
Furnace runs until 70 degrees
Maintains temperature for awhile - probably for a couple of hours
At some point it stops maintaining the temperature and keeps kicking on and off.
I've watched the thermostat - I'll actually turn the temp up to try to get it to kick in. The thermostat "flame" comes on, I'll hear it ignite, the furnace starts up and then runs for about 15 secs then shuts off. Thermostat calls for heat, igniter kicks in, furnace starts and runs for 15 secs then shuts off. So the Temperature isn't maintained.

If I shut the heat off on the thermostat, wait 10 seconds, then turn the heat on again - the whole cycle will start over again.

When I get home from work it is like 58 degrees. I shut the heat off, then on, then the furnace will stay on. I go to bed and wake up in the middle of the night and the temperature is in the low 60's.

A friend of mine does heating/air for a job but he usually works on commercial buildings. He has come over and tried a few different things but it keeps doing the same thing.

I read another answer to someone in the q&a section about the flame sensor being dirty and I'll mention that to him but I'm sure he has probably checked that. At one point he thought it might be a thermostat problem - so I'm going to buy a new one.

Is there anything else that can cause these symptoms?

I noticed a time delay fuse next to the on/off switch on the furnace - could that have anything to do with what is going on?

It is -8 in Minnesota right now and I just want to make sure my furnace stays on this week-end. My friend is going to come over tomorrow and take a look at it again.

Thanks,
Chris

Oh - the brand of the furnace is Amana

I doubt very much that it is a thermostat problem. Has your friend checked your high limit switch yet? I'd go there next.

There is some great advice at https://www.askmehelpdesk.com/heating-air-conditioning/heating-cooling-maintenance-repair-troubleshooting-frequently-asked-questions-58313.html

It includes the tip of jumpering the red and white wires to isolate a thermostat problem. If the furnace won't come on and stay on with the red and white wires connected, the problem isn't the thermostat.

Read up on flame sensors in the stickies. I can't imagine the high limit sensor tripping so quickly.

Also, does you furnace flash a trouble code? They can be a great help in identifying the problem.

I believe he did check the high limit switch. I do not believe that my furnace flashes a trouble code. He wasn't able to come out today. I'm hoping he can get over here tomorrow.
Thanks for the ideas!

Chris

A pressure switch will have this symptom, dirty flame sensor, dirty burners, clogged or froze drain if 90% furnace. Its hard to say with out more info. Good luck .

This is the way a 90% will operate with a slow drain problem.