Furnace - no flame (sometimes)

8543 Views 35 Replies 8 Participants Last post by broadripple, Jan 15, 2016

broadripple

Discussion Starter · Jan 3, 2016

Hello to all,

I am looking for some feedback/suggestions regarding my Trane XE 80 furnace. The furnace is about 22 years old and running strong for the most part

. About 4 weeks ago, my furnace would heat intermittently ... might run fine for a few days and then stop. After a quick reset, the heat would come on and all was well. I decided to change the filter, clean the flame sensor, and check the thermostat (basic digital Trane thermostat w/o batteries).

Everything was fine for until this morning when I noticed the heat stopped again. This time I check the status indicator before attempting to reset the unit and noticed 2 flashing lights which tells me 'System Lockout (no flame) / check polarity.'

I reset the unit and see the call for heat using the status indicator (fast flashing light) ... I see the ignitor light up and hear what sounds like a switch which I assume is the gas kicking on ... the ignitor stays on for about 10 seconds before it turns off without lighting anything. This happened 3 times and then it locked out again. I toggled the gas switch off and back on and lightly tapped the box that holds the switch. After hitting the reset switch, everything worked as expected.

I am not certain what to make of it. I suspect a faulty board/switch? I appreciate any thoughts. Thanks! :biggrin2:

1 - 20 of 36 Posts

roughneck

· #2 · Jan 3, 2016

What's the voltage at the valve when this happens? What's inlet gas pressure?

beenthere

· #3 · Jan 3, 2016

Could be an intermittently sticking gas valve, dirty burners, or a heat exchanger problem.

broadripple

Discussion Starter · #4 · Jan 3, 2016

roughneck said:
What's the voltage at the valve when this happens? What's inlet gas pressure?

Thank you for the reply. Unfortunately, this is beyond my toolbox

. Perhaps this is a good time to call-in an expert in the field?

broadripple

Discussion Starter · #5 · Jan 3, 2016

beenthere said:
Could be an intermittently sticking gas valve, dirty burners, or a heat exchanger problem.

Thank you for the reply. If sticky gas valve, is this something I can clean/check (along with dirty burners)? I suspect if there is a problem with the exchanger, I would need to call-in an expert in the field.

I consider myself a very handy person but not an expert in hvac

. I am not opposed to calling out someone who it an expert in hvac, but would like to know that I have done all I can with my limited knowledge before doing so

.

roughneck

· #6 · Jan 3, 2016

To troubleshoot you'll need tools, a decent multimeter at the least. Otherwise you'll just be guessing and blindly throwing random parts at the unit.
Troubleshooting can involve working with live gas and electricity. So you need to be ok with that.

broadripple

Discussion Starter · #7 · Jan 3, 2016

roughneck said:
To troubleshoot you'll need tools, a decent multimeter at the least. Otherwise you'll just be guessing and blindly throwing random parts at the unit.
Troubleshooting can involve working with live gas and electricity. So you need to be ok with that.

Thanks for the quick reply. I have a basic multimeter and feel relatively solid with electricity but have not done much with gas. I created a video a few weeks ago detailing my furnace along with some basic troubleshooting steps (I do this to help myself down the road if needed

) ... the video can be found here:

a.man1302

· #8 · Jan 3, 2016

Using a multimeter you have to verify that you are getting the correct voltage at the gas valve... given the age of the furnace ir sounds like your gas valve is stuck closed and not opening to allow burners to start... if you have the correct voltage at the gas valve then your gas valve is bad... if you dont then you have to figure out why.

broadripple

Discussion Starter · #9 · Jan 4, 2016

a.man1302 said:
Using a multimeter you have to verify that you are getting the correct voltage at the gas valve... given the age of the furnace ir sounds like your gas valve is stuck closed and not opening to allow burners to start... if you have the correct voltage at the gas valve then your gas valve is bad... if you dont then you have to figure out why.

Thank you ... what is the correct voltage?

roughneck

· #10 · Jan 4, 2016

Voltage is 24V

broadripple

Discussion Starter · #11 · Jan 5, 2016

No heat this morning, so time to take a closer look

. I created the following video to better demonstrate the challenge. roughneck - thank you for the voltage. Should the voltage be static/consistent or only when the switch is given? When idle, I see zero (providing I am measuring from the right wires

). Any additional information is greatly appreciated. Thank you!

broadripple

Discussion Starter · #12 · Jan 5, 2016

After chatting with a few people, I am relatively certain the value needs to be replaced. Does anyone know of a good fee/estimate for this? Thank you!

roughneck

· #13 · Jan 5, 2016

Is the gas valve getting voltage to open? If so is there gas pressure on the outlet side of the valve?
Don't want to guess and throw parts at the unit without knowing exactly what's wrong. You'll end up spending more $$$$ then if you just hired a professional technician.

broadripple

Discussion Starter · #14 · Jan 6, 2016

roughneck said:
Is the gas valve getting voltage to open? If so is there gas pressure on the outlet side of the valve?
Don't want to guess and throw parts at the unit without knowing exactly what's wrong. You'll end up spending more $$$$ then if you just hired a professional technician.

Heat went out last night. I hooked my multi-meter to the gas value and reset unit. When the unit when the switch was flipped, the multi-meter went from z to 1.4-1.6 which does not seem right

. The gas came on and flames lit. I suspect I am doing something wrong

.

roughneck

· #15 · Jan 6, 2016

If the unit successfully lit, then the gas valve should have 24 V at the main valve terminals.

broadripple

Discussion Starter · #16 · Jan 7, 2016

roughneck said:
If the unit successfully lit, then the gas valve should have 24 V at the main valve terminals.

After taking a closer look and retesting, I am getting 24-26 which seems solid.

jkc31

· #17 · Jan 7, 2016

If your going to listen to people telling you made up stuff like your gas valve is sticking then why would you even use it? Wiggle the white connector where the wires go into the gas valve when you know the gas should be coming. You'll hear clicking sounds coming from the gas valve. It may even light if you push it to one side. There are pins that the connector plug into. These pins are attached to a pcb. Most of the time the solder joints crack and don't make a good enough connection to the pcb. You can remove the black bracket of the gas valve and access the board. Re-flow the cracked joints and it will work without pause.

roughneck

· #18 · Jan 7, 2016

jkc31 said:
If your going to listen to people telling you made up stuff like your gas valve is sticking then why would you even use it? Wiggle the white connector where the wires go into the gas valve when you know the gas should be coming. You'll hear clicking sounds coming from the gas valve. It may even light if you push it to one side. There are pins that the connector plug into. These pins are attached to a pcb. Most of the time the solder joints crack and don't make a good enough connection to the pcb. You can remove the black bracket of the gas valve and access the board. Re-flow the cracked joints and it will work without pause.

Most gas valves are not field serviceable, and say so on the valve itself. If this is the case the valve should never be dismantled. If it is it should never be used.
The OP should verify its the gas valve with a meter and monometer before attempting to repair something he hasn't verified as defective yet.

broadripple

Discussion Starter · #19 · Jan 8, 2016

roughneck said:
Most gas valves are not field serviceable, and say so on the valve itself. If this is the case the valve should never be dismantled. If it is it should never be used.
The OP should verify its the gas valve with a meter and monometer before attempting to repair something he hasn't verified as defective yet.

I agree. After confirming voltage, I decided to replace the gas valve. I hired someone to do the job as I have not worked with gas (outside of my grill

). The valve was replaced today, and I will keep you posted. Thank you for your help and guidance ... much appreciated!

broadripple

Discussion Starter · #20 · Jan 9, 2016

I had the valve replaced yesterday and captured the job on video. So far, so good. Thanks to everyone for their help.

1 - 20 of 36 Posts

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