Originally Posted by lylelanley
The nightmare which has been my furnace will not end.
Last week, I turned my furnace on for the first time of the winter season. Right away, the furnace didn't light, the repairman said that it was a faulty valve, and it needs to be replaced.
I give the go-ahead and the by the end of the day he call to let me know that he had put in two new valves and a new board, and still it didn't want to work.
He said that at this point (when figuring all of the labor $ that has gone into it so far) it would probably be better to just get a new furnace alltogether. I was torn, the one that he was working on wad 6 years old, not exactly new, but not old. I told him to get one ordered up and he said that it would be a few days before he could get it installed.
In the mean time, I had called the gas company to come out and just take a look at the lines to the furnace, just to make sure those were ok. They were, but in talking to the guy, he told me about taking a look at the manifold, just to make sure that the holes for the gas are clear.
He took a thin wire and cleaned it out. Sure enough, the damn furnace roars to life. All is good on this earth. I have heat. I was in the process of calling the repairman (who, was recommended to me by two seperate friends) when I noticed that the damn thing wont stay on for more than 2 minutes without shutting itself off and starting back again in a continuous cycle. The repairman comes back out and acuter taking a look at it he is totally stumped. He doesn't know what the problem is.
He still reccomends the new install that would solve all of the problems that I am having with the furnace, and after getting a pretty fair deal for the unit and install, the new one went in. I get a call at the office from the repairman, and he says it is installer and it is running like a top. I get home, it had brought the temp in the house up to 70 and so I shut it off because it was an unseasonably warm day.
I go to turn it on again today, and I have the same problem! It is caught in this unending cycle of running for 2 minutes, shutting off, and then immediately starting back up again. What the hell is going on? I'm about to go crazy! Please help with any advice.
tl;dr. After installing a brand new furnace because the old one was constantly cycling on and off every couple of minutes I am still having the same problem! What is possibly wrong with my hvac system?
This problem is a typical one and a good qualified TECH should diagnose it quickly and accurately. Im not there so i dont know which it is, but here is a menu of items that it could be :
1. The flame sensor is not in the flame sufficiently.
2. Flame sensor is weak or defective not putting a strong enough signal for proper gas valve operation.
3. Flame sensor rod is carboned up and needs cleaning well.
4. Thermostat on the wall has a misadjusted cycle rate setting / too low of a heat anticipator setting for the furnace.
5. Burner ports are still partially plugged not allowing proper crossover of ignition from one burner to the next door one.
6. Partialyl plugged vent pipe causing a trip of the air pressure switch which in turns shuts down the gas valve for safety.
7. Faulty air pressure switch.
8. Very dirty air filter restricting airflow causing the limit switch to trip the gas valve.
9. Insufficient return air from the house to the furnace due to undersized return air / supply air ductwork.
10 . If the furnace is a condensing type 90 % + efficiency, the condensate is backing up and not draining correctly out of the exhaust vent pipe and/or the secondary heat exchanger inside the furnace causing a trip of the air pressure switch.
Get a qualified Tech. to determine which it is.