Troubleshooting Payne propane furnace blower fan constant but no heat

[Zen]

Just as it gets cold, my Payne hot air propane-fired furnace broke!

All of a sudden, the blower just blows cold air constantly without letup. The pilot flame never starts. Obviously, the gas never lights up either.

This happened, all of a sudden.

Normally, it has an electronic pilot, which lights the gas about a minute after the blower starts. There is plenty of propane.

Any troubleshooting ideas?

I think there are three main components:

1. The flame apparatus
2. The circuit board
3. The lockout switch

I'm inclined to just buy all three, and replace (and have a spare), since I remember the last service call was expensive and the circuit board was replaced in seconds after a three week wait for the parts to arrive.

Do you have any idea WHERE I can get the three main components?

[trader4]

Some observations:

I don't know how your furnace is designed or hooked up. But I've never seen a forced air furnace where the blower goes on for a minute BEFORE the furnace fires. Every one I've ever seen works exactly the opposite. The burner fires FIRST and then the blower comes on a minute or so later. That avoids the furnace blowing cold air. The blower is triggered either by a temperature switch in the plenum or by a control board.

It's usually not a good idea to just start replacing components randomly. Regarding the list of suspects:

1. The flame apparatus

what's that? the actual burner assembly?

1. The circuit board
2. The lockout switch

Which lockout switch? There typically are several mechanisms involved. If it's a simple switch, it can be bypassed for test purposes instead of just replacing it on the theory it might be bad. And if it's the switch on the blower compartment, in the furnaces I've worked on, that switch only disabled the blower. The fact that the blower works tells you that switch is OK.

First area I'd be looking into is if the ignitor is activating, ie is it trying to light at all? That's the first step in the process and the ignitor going bad is one frequent source of problems.

[Stormin Mormon]

Sorry to hear your furnace went out. I'd suggest to call your friends and relatives, and see who they hire for furnace repair. Home furnace isn't a good place to learn on. Too many things can go wrong.

Christopher A. Young Learn more about Jesus

.

This happened, all of a sudden.

Normally, it has an electronic pilot, which lights the gas about a minute after the blower starts. There is plenty of propane.

Any troubleshooting ideas?

I think there are three main components:

1. The flame apparatus
2. The circuit board
3. The lockout switch

I'm inclined to just buy all three, and replace (and have a spare), since I remember the last service call was expensive and the circuit board was replaced in seconds after a three week wait for the parts to arrive.

Do you have any idea WHERE I can get the three main components?

[Vic Smith]

Don't waste money throwing parts at it. Get the model number, then post this with model number to alt.hvac. You might get troubleshooting procedures there. If not, get the manual which should allow you to pinpoint the problem. For parts, just google the model number.

[DD_BobK]

I would have agreed with T4 on his commentary UNTIL I watched this YouTube video.

seems like a blower (gas combustion related) comes on first, then the unit fires up.

I guess my question is "which blower" does the OP refer to?

The YouTube search function aint great and this furnance isnt the OP's make/ model but it might be helpful.

cheers Bob

[trader4]

tp://www4.picturepush.com/photo/a/11964117/img/11964117.jpg

The video clearly states that it's the "vent stack blower" that's coming on. It's a newer, higher efficiency furnace. The blower is actually called an inducer blower.

Since the OP said that the furnace blower blows cold air and there is no evidence of an inducer blower in the pic he supplied, I assume it's the air handler fan that he's tallking about when he refers to the blower a second time.

But, then George here gets all upset if one makes what appear to be reasonable assumptions when responding to a question. According to George, I'm not supposed to answer, only ask for "clarification".

[sms]

Probably a bad idea to just start replacing parts.

It's strange that the main blower starts up at all, because normally it doesn't start until after the flame is detected by the flame sensor and the burners start (so it doesn't blow cold air), unless you have the fan always on at the thermostat.

The sequence should be:

1. Draft inducer fan starts up and closes switch (via suction) so the controller knows that the draft inducer is operating and it's safe to light the burner. You can check this with an ohm meter, or jumper across it to test it (however it must be open when the furnace starts, then closed after the draft inducer fan starts, you can't jumper it closed before the draft inducer fan starts).
2. Glow plug heats up (or spark ignitor starts sparking). You can check that a glow plug is getting power with a voltmeter (should be 24VAC) and you can see it glow red. A spark ignitor should make a noise.
3. Gas valve opens and burners ignite. Audible thunk as the solenoid is activated. Controller knows that the burners are lit by looking at the flame sensor and will close the gas valve after a short time if there is no flame. You can test the gas valve by turning off the gas to the furnace, unplugging the wires to the valve, and connecting 24VAC or so to the valve from a small transformer. If you hear a thunk then the solenoid is activating and the gas valve is probably okay.
4. Main blower starts up.

If one of the flame-out sensors is bad (open) the gas valve won't turn on. There are usually three or four flame-out sensors in series. If there's a crack in the heat exchanger then flames can shoot out the front of the furnace and the flame-out sensors will shut off the gas.

When my furnace broke a couple of months ago it was an intermittent gas valve.

When my friend's furnace broke last month it was an intermittent draft inducer fan switch (sometimes it's just a clogged suction hose, but this time the switch was bad).

If it's an older furnace with relays on the controller board you can hear the relays click as various things are activated. The draft inducer fan relay will click, the ignitor relay will click, and the gas valve relay will click.

[trader4]

Agree, IF it has an inducer. From the picture, there was no evidence of one. It looks like an older furnace.

Yes, usually after a delay of a minute or so

[sms]

broke!

>

components?

>

That's the draft inducer fan. The furnace won't start at all unless that fan is running. There's a tube going to a suction activated switch that indicates that the draft inducer fan is running. My friend's furnace had an intermittent draft inducer switch and sometimes would not start at all, sometimes would start and run for a while then stop.

I suspect that the reason that the main blower is running is that the OP has it turned on at the thermostat, i.e. "Fan On" instead of "Auto."

[Vic Smith]

Don't know. It was just a suggestion. There are internet forums too. This seems generally polite to DIY'ers.

main point was to DIY you should have model number and/or a manual as your starting point.

[hrhofmann]

Are you sure the unit is not in the air-conditioning mode?????

[Stormin Mormon]

If you look at the pictures OP provided, you can see how many blowers the furnace has, and what their function are.

Christopher A. Young Learn more about Jesus .

I guess my question is "which blower" does the OP refer to?

The YouTube search function aint great and this furnance isnt the OP's make/ model but it might be helpful.

cheers Bob

[Stormin Mormon]

Also helpful to view the photos provided by OP.

Christopher A. Young Learn more about Jesus

.

I would have agreed with T4 on his commentary UNTIL I watched this YouTube video.

seems like a blower (gas combustion related) comes on first, then the unit fires up.

I guess my question is "which blower" does the OP refer to?

cheers Bob

[Stormin Mormon]

You didn't view the photos, either.

How many blowers on an old 70 percenter with gravity draft?

Christopher A. Young Learn more about Jesus

.

Since the OP said that the furnace blower blows cold air and there is no evidence of an inducer blower in the pic he supplied, I assume it's the air handler fan that he's tallking about when he refers to the blower a second time.

[trader4]

By my count there is only one blower, the one that serves as the air handler. Yes?

[Stormin Mormon]

A few points.

The OP gravity draft furnace doesn't have inducer fan.. sip your martinis, don't gulp them. Blower all the time might be a bad fan limit switch. Ten commandments, not twelve. The "glow bars" I've seen have been 110 VAC. We refer to her as Virgin Mary, not Mary with the Cherry. You don't sound like you know furnace troubleshooting. We refer to Father Son and Holy Ghost, not Dad, JC, and the spook.

Christopher A. Young Learn more about Jesus

.

Probably a bad idea to just start replacing parts.

It's strange that the main blower starts up at all, because normally it doesn't start until after the flame is detected by the flame sensor and the burners start (so it doesn't blow cold air), unless you have the fan always on at the thermostat.

The sequence should be:

1. Draft inducer fan starts up and closes switch (via suction) so the controller knows that the draft inducer is operating and it's safe to light the burner. You can check this with an ohm meter, or jumper across it to test it (however it must be open when the furnace starts, then closed after the draft inducer fan starts, you can't jumper it closed before the draft inducer fan starts).

1. Glow plug heats up (or spark ignitor starts sparking). You can check that a glow plug is getting power with a voltmeter (should be 24VAC) and you can see it glow red. A spark ignitor should make a noise.

2. Gas valve opens and burners ignite. Audible thunk as the solenoid is activated. Controller knows that the burners are lit by looking at the flame sensor and will close the gas valve after a short time if there is no flame. You can test the gas valve by turning off the gas to the furnace, unplugging the wires to the valve, and connecting 24VAC or so to the valve from a small transformer. If you hear a thunk then the solenoid is activating and the gas valve is probably okay.

1. Main blower starts up.

If one of the flame-out sensors is bad (open) the gas valve won't turn on. There are usually three or four flame-out sensors in series. If there's a crack in the heat exchanger then flames can shoot out the front of the furnace and the flame-out sensors will shut off the gas.

When my furnace broke a couple of months ago it was an intermittent gas valve.

When my friend's furnace broke last month it was an intermittent draft inducer fan switch (sometimes it's just a clogged suction hose, but this time the switch was bad).

If it's an older furnace with relays on the controller board you can hear the relays click as various things are activated. The draft inducer fan relay will click, the ignitor relay will click, and the gas valve relay will click.

[Stormin Mormon]

About time!

Christopher A. Young Learn more about Jesus

.

Agree, IF it has an inducer. From the picture, there was no evidence of one. It looks like an older furnace.

[Stormin Mormon]

I'll roger that!

Christopher A. Young Learn more about Jesus

.

By my count there is only one blower, the one that serves as the air handler. Yes?

[trader4]

It's not up high on the furnaces I've seen. They have sealed combustion chambers, with the inducer blower in the compartment with the gas valve. Those would be visible in the photo. Also, the combustion air inlet area in the photo is clearly not sealed. These are

90%+ furnaces of the last decade.

Are there other furnaces where the inducer blower is not located in the compartment in that photo, but is higher up, like on the exhaust, more like what you see with a power vented water heater?

Aside from that, given the way it looks, rust, etc, would lead me to believe it's probably just a conventional vented furnace.

[Stormin Mormon]

I went back and looked at the photos. That design is totally obvious to me, it's a gravity draft 70 percenter.

Christopher A. Young Learn more about Jesus

.

Can't tell because the draft inducer fan is normally high up, above where the photo stops.