Furnace repair help

[checkthisout]

View media item 106920
Notice the relay in the upper right. It's actually in the lower right but I rotated the pic.

Furnace won't come on. The combustion blower grunts for a second and will begin to spin slowly if assisted.

Ultimately no sparking at the igniters.

I assume the relay is for the combustion blower.

If the combustion blower doesn't spin then no draft is detected and then no spark command is initiated and thus no gas flow?


Replace control board and re-test? I almost want to buy a relay and replace the one in question. No time for that though.

 

[rob1200]

My furnace control board has a red LED that flashes in patterns to indicate various problems.

Is your board indicating any problems?

 

[rct]

I had the power vent blower die a few years ago, during a cold spell. Hvac co had one on the truck.

 

[Jim greengo]

Yep,if inducer motor doesnt run the pressure/vacuam switch wont close.
You can pull inducer motor/housing off to make sure it's not packed full of dead birds.

 

[Whitworth]

Hot wire it direct (230v?) and see if it runs. May be a bad bearing.

 

[Jim greengo]

Hot wire it direct (230v?) and see if it runs. May be a bad bearing.

Inducer motor should be 120v,not 240.

 

[RossABQ]

Google your furnace model for a manual. Recently did this for mine and it tells how to run a self-diagnostic that tests major components (except burner). As said, the LED's will flash a code.

 

[dmdc411]

If its a Lennox furnace, its a common failure to lose the relays. White-Rogers makes a better replacement for less $$$. But you need to have a WR igniter when using their board.

Sent from my SM-G970U using Tapatalk

 

[dogdog]

Relay looks burned. Just stating the obvious... It's burn probably what ever it is controlling is drawing too much current or it's been restarted too frequent, they do have in rush current... (happened to me on one of the board and the circuit board trace burned instead of the relay)

so.. you might want to check out that component it was controlling first and see... otherwise you might be throwing boards at it.

 

[checkthisout]

Well, I just went ahead ordered the board in a well aimed shotgun repair.

I figure the board needs replacement regardless of whats actually wrong with it or not due to the obviously smoked relay.

The inducer fan turns freely. I was in a hurry and forgot about the diagnostic flash. Usually the instructions are on a label inside the furnace. I'll **** around with it when I go to install the board.

Got a new board for $120.00

 

[checkthisout]

Hot wire it direct (230v?) and see if it runs. May be a bad bearing.

Yeah. On a time crunch and didn't have anything with me. I'll take jumper wires and my fluke with me when I go to install the board and give everything a quick test before replacing it.

The motor spun easily by hand and no rumbling or excess play. Do those motors have bearings? Looked to me to stainless/bronze bushing setup.

 

[nadogail]

About 20 years ago, my gas utility sent a technician to troubleshoot a furnace and I was able to get a nice discount on the part and installed it myself.

 

[GirchyGirchy]

Were you getting voltage at the exhaust fan motor? Since it is making noise and tries to turn, i would guess you need one of those as well. But would need to verify voltage first and try to test it with 120v.

It's not igniting because it's not seeing anything from the pressure switch. You could short that switch's output temporarily to test the rest of the system. Note it needs to see the short after it tries the exhaust blower...probably won't turn on the exhaust if it sees that pressure switch first.

 

[Fordguy1964]

Were you getting voltage at the exhaust fan motor? Since it is making noise and tries to turn, i would guess you need one of those as well. But would need to verify voltage first and try to test it with 120v.

It's not igniting because it's not seeing anything from the pressure switch. You could short that switch's output temporarily to test the rest of the system. Note it needs to see the short after it tries the exhaust blower...probably won't turn on the exhaust if it sees that pressure switch first.

You have to be VERY careful doing that. If you do not have the draft inducer running the gas just sits there and doesn't travel out towards the "flue" and will likely flash back into your face when it ignites. This is not something that I would suggest a novice try.

 

[ripperd]

Well, I just went ahead ordered the board in a well aimed shotgun repair.

I figure the board needs replacement regardless of whats actually wrong with it or not due to the obviously smoked relay.

The inducer fan turns freely. I was in a hurry and forgot about the diagnostic flash. Usually the instructions are on a label inside the furnace. I'll **** around with it when I go to install the board.

Got a new board for $120.00

Good decision. Those boards only last so long. The next component to fail was probably not long behind the first one.

I did the exact same thing to keep a 15 year old furnace going. $120 to get a few more years out of it is a steal.

 

[sarman47]

My furnace crapped out a few years back, the red flashing code light lead me in the direction of a new board.

I purchased my board from https://www.repairclinic.com/

Installed and all worked fine.

Make sure you have good pictures of all the wiring connections for reference. Or do it one for one.

Hopefully the board will fix your problems.

 

[checkthisout]

You have to be VERY careful doing that. If you do not have the draft inducer running the gas just sits there and doesn't travel out towards the "flue" and will likely flash back into your face when it ignites. This is not something that I would suggest a novice try.

I'm not sure about this though. Should a man over 40 years old be using emojis???

 

[getbent4x4]

need to test blower motor for power and see what type it is. If it's a non capacitor blower motor good chance it could be bad.

 

[checkthisout]

Ordered a new board off Amazon. The vendor, an HVAC parts dealer sent it in a bubble envelope. What the hell man?

Got a different one ordered from someone else.

View media item 107138

 

[checkthisout]

Installed new board today. Didn't work.

Resortrd to reading the directions that came with the board and got it working.

House is sweaty again.

 

[carlosh]

Installed new board today. Didn't work.

Resortrd to reading the directions that came with the board and got it working.

House is sweaty again.

What did the instructions say to do?

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[niget2002]

What did the instructions say to do?

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That's usually 'man code' for "I put the wires on the wrong plug"

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[checkthisout]

What did the instructions say to do?

Sent from my SM-G965U using Tapatalk

Had to move the heat wire from W2 to W and install an alternate bonding wire on the circuit board.

Then move the high/low speed jumper from none to 5 or 12.

 

[checkthisout]

That's usually 'man code' for "I put the wires on the wrong plug"

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That's what I have learned over the years.

When all else fails, read the directions.

 

[yeldogt]

Did you discover any reason why the relay fails .... Now it could be a poor design ... but, often this is caused by an increased load. Does it point to a failing motor ?

If so the motor will cause the new board to fail in the same way.

 

[checkthisout]

Did you discover any reason why the relay fails .... Now it could be a poor design ... but, often this is caused by an increased load. Does it point to a failing motor ?

If so the motor will cause the new board to fail in the same way.

My assumption is that it controlled the combustion blower.

That blower worked on both high and low speeds after the repair and would begin to spin slowly (if assisted) with the old, burned up board.

I think the furnace was an 03 or 05 so 15 or 17 years old and that was the original board.

The combustion blower kicked right on with the new board and settled right into low speed then back to high. The relays did not get warm to the touch.

Charged my Mom $400.00, a can of diet Pepsi and beef Jerky stick and left.

 

[gungatim]

LGR!

 

[checkthisout]

get ready to buy a new combustion blower in a month or so. this is one sign...btdt.

What goes bad on the blower to cause the high draw?

 

[dogdog]

What goes bad on the blower to cause the high draw?

It could just be because of the cycling too much... I have changed a board on the power exhaust before because the furnace was cycling too much. blower was still fine till it just corroded away.. literally .... but that might be different case than yours....

 

[dogdog]

That's usually 'man code' for "I put the wires on the wrong plug"

Sent from my LM-G820 using Tapatalk

LMFAO... didn't know there was that "man code"

you should start a thread about man codes. would be interest in other man code.

 

[checkthisout]

Well, I would assume it's also possible that the relay contacts went bad over time as relay contacts often do?

Whenever a relay goes bad on a furnace board is it protocol to the replace the motor it was controlling?

A bad component shouldn't fry a relay unless the circuit is overfused. It would seem to me that relays go bad due to the contact points oxidizing and wearing overtime causing high resistance in the relay itself which would lead to burned contacts and burned up relay.

No?

 

[dogdog]

it's not but check it at least to see if it spins freely? If there are drags on the motor like dried up grease would have cause more current draw... or it might be a combination of both. Me... I fix it till I break it. I think the other guy is just asking you to check the components ... if it is fine then fuhgettaboutit...

 

[gungatim]

What goes bad on the blower to cause the high draw?

LGR!

 

[checkthisout]

they get dirty and clog on the shaft bearing gets stiff, they can't start without spinning by hand or fresh boards/relays. pull it apart and take a look. bet it's full of soot.

A gentle spin with the hand without any power to it would make it spin for like 20 seconds or so.

Appreciate the tip though. I'll put a motor in my Save For Later cart on ebay just in case.