Ask Me Help Desk - Furnace won't keep running

Furnace won't keep running

I have a programmable thermostat. In the morning when the furnace comes on it will run for one cycle and then stop. In order to get it to start again, I have to turn off the heat and then turn it back on again. I have had technicians out several times. They have replaced various parts and things work fine for a while and then the same problem starts. I have tried different thermostats with no luck. Some say it's a venting issue. Some say a short in the wire from the thermostat to the furnace. I don't know. The furnace ran fine for about 10 years. I can't believe it is now a venting or wiring problem. Any ideas.

Have they replaced the circuit board in the furnace? They are fairly expensive, but the most likely thing to be causing the problem other than the thermostat.

THe first repairman replaced the circuit board. Another replaced a sensor that turns off the burner when it get too hot. The latest reparman from the locat utility company thinks it might be a problem with the blower being plugged. The burner gets too hot and the furnace shuts down until it cools off enough or I reset it by turning off the furnace and turning it back on. I don't know, but it's getting frustrating. At least I have heat if I leave the thermostat at a constant temperature.

Quote:

Originally Posted by jhuemmer

I have a programable thermostat. In the morning when the furnace comes on it will run for one cycle and then stop. In order to get it to start again, I have to turn off the heat and then turn it back on again. I have had technicians out several times. They have replaced various parts and things work fine for a while and then the same problem starts. I have tried different thermostats with no luck. Some say it's a venting issue. Some say a short in the wire from the thermostat to the furnace. I don't know. The furnace ran fine for about 10 years. I can't believe it is now a venting or wiring problem. Any ideas.

More information would be very helpful. You said its 10 years old, is it a 90% or 80% efficient furnace. Is it on L.P. or natural gas? What brand name? It doesn't sound like this should be to difficult to diagnose, maybe you need a new HVAC contractor. See my other posts about air-flow. You may also need to go to the furnace and roughly time the cycles. It should be like this. First the draft inducer motor starts, (60 seconds or so) then the ignition device starts, (Direct ignition, hotsurface ignition, honeywell smart valve?) The gas valve will open and burner starts. After heat exchanger is warm the main blower will start. Is the gas still burning? What is the temperature rise? Did the main limit open? Many furnaces will flash a code on the circuit board if the limit does open.
I hope this helps and I will try to check back soon.

The furnace is a Ruud Deluxe 90 Plus. It was installed when the house was built in 1993. It runs on natural gas. The repairman from the local utility company has been out to look at it. He found that the hose that drains condensation was plugged and replace that. That didn’t fix the problem. He then bypassed the thermostat and found that the furnace would quit because the limit switch would shut off when the furnace got too hot. He thinks there may be a problem with the blower being partially plugged. He plans to stop back and look at it.

Since the last time he was here I have noticed that the furnace will occasionally run through more than 1 cycle before it quits. The blower will shut off for about 10 – 20 seconds and then start up again. The burner is going during this time. Other times it runs 1 cycle then stops and I have to shut off the thermostat and turn it on again to get the furnace to run.

Two things I have noticed lately – 1. The furnace used to make a clunking sound, similar to someone hitting the ductwork, when the blower would stop. I always thought this was the metal contracting when it cooled down.(My sister recently replaced her furnace and the technician told her there was no trap door on the new model so she would not here that sound anymore. Is this true? Is there some kind of door on the vents?) 2. When the furnace shuts off normally, when the proper temperature is reached, I here a click in the thermostat. When the furnace is not running properly and shuts off prematurely, I don’t here the click.

Hope this helps.

Trap door? Which drain hose was plugged, the one to the secondary heat exchanger or the one to the flue pipe? Did he clean the trap good? And the port on the bottom of the flue pipe? Is there any water in the pressure switch or vacuum hose? There is an amber light on the PC board, make sure it turns on steady, to be sure it is sensing a flame. Is this a "Drum" furnace? Also if furnace is overheating check for a plugged secondary, evaporator coil, filters, registers open, and cold air returns unobstructed.

Good luck

I am having the same problem if someone figures out what your problem is please email me and let me know.
Thanks G.

Quote:

Originally Posted by gwright

I am having the same problem if someone figures out what your problem is please email me and let me know.
Thanks G.

I alredy stated many of the possibilities in this thread.

I have the same problem and came to the conclusion that all of us are "Jack of All Trades" and "Masters of None". Call a reputable HACV, and let them do what they do best.

I had the same problem as all of you above... I came to the conclusion that we all are "Jack of All Trades" and "Masters of None". My advice is to call a reputable HVAC technician and let them do what they know best. As far as the rest of us, let's do what we do best. We probably all can make more money doing what we do for careers, for the same amount of time invested in trying to figure out the problem which all of us don't have a damn clue.