York Diamond 80 furnace on the fritz

[Kato2]

I have a 5 year old furnace York Diamond 80 that will fire up then stop leaving one to think it's the flame sensor that's the problem then it will burn fine the next time, stop when the temperature set on the thermostat is reached and start again within a few minutes.
This is happening very randomly at all different times in the schedule set in the thermostat. We changed the thermostat as advised by a serviceman but it still happens.
Anyone have ideas please.

[Frankie3s]

If it's not the flame sensor then it could very well be the gas valve that is acting up and it might need to be changed. I've had the problem that you are describing and in the end the problem was exactly that, the gas valve had to be changed.

I think what contributed to my gas valve's demise was that I had installed a new Honeywell thermostat and it was simply too sensitive (the furnace would come on every five minutes). The next time winter rolled around the valve need to be replaced.

I replaced the gas valve last winter (problem solved) and this November got rid of the Honeywell thermostat and replaced it with this one I bought at Costco for $50 plus tax, http://www.luxproducts.com/thermostats/tx9000ts.htm and it's touch screen too. Damn good thermostat and furnace is working beautifully.

[Kato2]

The thermostat I replaced was a Honeywell but I replaced it a one from Costco unfortunately it was a Honeywell as well hope it's not to sensitive.
Could you give me an idea of the cost involved with your repair.
Thanks.

[Munchos]

I have a 5 year old furnace York Diamond 80 that will fire up then stop leaving one to think it's the flame sensor that's the problem then it will burn fine the next time, stop when the temperature set on the thermostat is reached and start again within a few minutes.
This is happening very randomly at all different times in the schedule set in the thermostat. We changed the thermostat as advised by a serviceman but it still happens.
Anyone have ideas please.

I love how its always the thermostat's problem. There could be so many different reasons as to why this is happening that to actually solve the problem properly you should get someone to come check it out. Off the top of my head: bad board, pressure switch, inducer motor, gas valve, thermostat (I highly doubt it was the problem from the beginning), venting issue, blower motor(not enough rpm's for proper airflow), flame sensor, safety switch is opening up, etc...

Plus intermittent problems are and can be difficult to find the root cause of the problem.

[Kato2]

Munchos we had a serviceman come in that was his recommendation (replace the thermostat) at $200.00 these are my 85 year old parents (fix income) I did it for $60.00 the price of the thermostat.
The first gentlemen that serviced the furnace in all this changed a part with tubes to the inducer motor I believe, that did not fix the problem, then the thermostat still the problem persists.
I have checked the flame sensor and igniter they seem fine I was thinking the board back I am no expert you seem to know what your talking about are you an HVAC professional if so want to help.

[Frankie3s]

I doubt that its the thermostat too and simply listed it as a an item that caused my gas valve to eventually fail. The gas fitter/installer said that the furnace should not cycle more than 6 times max per hour and if it does, the home could either be too poorly insulated or the thermostat can be the issue; Most likely being too sensitive and will cycle on with less than a degree of temperature difference.

The problem with the Honeywell's is that you can't limit/program the cycling or temperature sensitivity as you can with the others such as the Lux one that I had bought at Costco. When the OP's issue is fixed he will need to monitor how often the furnace comes on. More than likely it could be an insulation issue and should be corrected. That gas valve makes a pretty good "thump" sound when opened and I'm sure 12 times an hour is not good for its health.

I got a deal on the replacement all-in it cost me $250 which was a bargain because everyone wants to charge a diagnostic fee $75 plus a service fee of $100 for coming out before doing anything else first. I only got this deal because the guy didn't want to come out that night and said that if I could wait until morning he'd cut me a some slack on the price.