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Billy
Billy, HVAC Technician
Category: HVAC
Satisfied Customers: 19947
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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troubleshooting payne furnace

Customer Question

troubleshooting payne furnace
Submitted: 4 years ago.
Category: HVAC
Expert:  Billy replied 4 years ago.

 

Hello,

 

yes the parts are available.

 

The initial test will be to see 120v is present terminal L1 and Neutral

 

Then if 24v is present from transformer on SEC1 and SEC 2

 

Then if all is ok...24v between terminal R and C at thermostat wire connections.

Customer: replied 4 years ago.
> Then if 24v is present from transformer on SEC1 and SEC 2

Across SEC1 and SEC2 or between each and ground?
Expert:  Billy replied 4 years ago.

 

Between sec1 and 2......sec 1 is 24+ and sec2 is 24-

 

one lead to each



Edited by Billy on 3/13/2010 at 5:36 PM EST
Customer: replied 4 years ago.
Okay, it's across SEC1 & 2

I've got 24 (27.5 actually) v on SEC1 & 2
and across R & C thermostat connections.

What's next?

BTW, when I now power up the unit one of the solenoids on the controller board connects for a second then all goes quiet.
Expert:  Billy replied 4 years ago.

 

Now check terminal R with one lead and terminal C with other. Should = 24v +

 

Then with stat turned up W and C = 24+

 

 

Customer: replied 4 years ago.
Yes I've got 27.5v across R & C.

With thermostat calling heat, I've got 19.8v across W & C

Expert:  Billy replied 4 years ago.

 

Use a short piece of wire or taped paper clip shaped in a U and touch the R terminal o the W terminal. Or if possible...actually screw it into place thus jumping R and W

Customer: replied 4 years ago.
Done.

(No response from furnace.)
Expert:  Billy replied 4 years ago.

 

Thank you.....

 

Is the exhaust fan running?

Customer: replied 4 years ago.
No. All is quiet.
Expert:  Billy replied 4 years ago.

 

There is a plastic plug that goes to the exhaust motor. Unplug and see if the 2 prongs in the supply side of the plug has 120 volt.

Customer: replied 4 years ago.
By exhaust motor, I assume you're referring to the caged, small fan, looks sort of like a computer fan that's located at the base of the exhaust pipe.

No, that plug shows < 1 v.
Expert:  Billy replied 4 years ago.

 

Thank you.

 

Upper section by motor is a round air switch with a rubber tube to it. Behind this switch is a small square circuit board that has 3 wires that attach to the round switch. Do you know the part and location I refer to?

Customer: replied 4 years ago.
yes
Expert:  Billy replied 4 years ago.

 

That is called and inducer circuit board.

 

Turn off power and remove the pressure switch to access the little board. See if there is a "hot spot" at about 2:00

Customer: replied 4 years ago.
No hot spot on the front side. I'll pull out the board and check the back.
Customer: replied 4 years ago.
No hot spot on back of circuit board.
Expert:  Billy replied 4 years ago.

Plug all back in, tap pressure switch to make sure it is not stuck. Then locate the wire that comes from the limit to the small circuit board. The wire that comes to the circuit board from the limit switch should have 24v with meter lead to it and one lead to cabinet

Customer: replied 4 years ago.
Just above the circuit bd., coming horizontally out of the base of the exhaust pipe is a 1" x 4" sheet metal box with what looks like a cut off switch. Is that the limit that you refer to?
Expert:  Billy replied 4 years ago.

 

This switch here behind the gas valve

 

Customer: replied 4 years ago.
Both leads from the limit go to the main board. ???
Expert:  Billy replied 4 years ago.

 

Sorry, you have first generation then.

 

But you should have an input to the small board from the big board

Customer: replied 4 years ago.
Directly from the main bd. there are only 2: a black and white and I assume they are line and common, and show 120v across them. (also 120 from B to cabinet, 0 from W to cab.).

Of the other 4, the wire from the cutoff switch (that I thought was the limit) shows 1.75v into the cutoff switch and slightly less from the cutoff into the inducer board. None of the other wires show any voltages.
Customer: replied 4 years ago.
Billy, I appreciate all your time. If we can resolve this I'll up my pmt to $30. In any case you've certainly earned the $15.
Expert:  Billy replied 4 years ago.

 

On main board...check LIM2 with one lad and the cabinet or ground with other lead.

Customer: replied 4 years ago.
There's no LIM2 on the main bd.

Can I email you a pic of my main board?
Expert:  Billy replied 4 years ago.
Yes please...you can attach here...use the tree icon at top of dialog page
Customer: replied 4 years ago.
graphic
Expert:  Billy replied 4 years ago.

 

Thank you...remember that one well. Have you removed the left side edge connector and checked the contacts?

Customer: replied 4 years ago.
Not yet, but I will.

Also, I pretty sure something burned out, because I was awakened at 5:00 this morning by a smoke alarm, and smelled something electrical burning. I would only smell it when the fan was on (manual). I checked the rest of the house, the smell went away, I turned off the power to the furnace and went back to bed.
Customer: replied 4 years ago.
All the contacts are clean on both the board and connector.
Expert:  Billy replied 4 years ago.

 

I did not have you check limits because the blower would be blowing....We know the transformer is ok.....It is either the main board or the inducer board. Just to cover the bases...jump out each limit and rollout.

Customer: replied 4 years ago.
> jump out each limit and rollout.

which means ???
Expert:  Billy replied 4 years ago.

 

The limit is what is on the front wall behind the gas valve. Here are the ones you would

 

 

another test at this time since you smelled something hot....with power on and door switch taped down....touch the R and the G terminal together and tell me if fan kicks on

Customer: replied 4 years ago.
Yes, I believe I found the limit, but what does "jump out the limit and rollout" mean? Is it to connect (jumper) the leads together and power it on?

Also, the fan does come on with R & G connected. (I still have R & W jumpered.)
Expert:  Billy replied 4 years ago.
jump out means to remove wire from limit and touch direct together hence bypassing limit...and the fan coming on is a good sign
Customer: replied 4 years ago.
Removing both limit leads causes the fan to run. Touching them together stops the fan.
Expert:  Billy replied 4 years ago.

 

Thanks....well it is definitely circuit board related. It may sound rudimentary...but do either board have the sulfur smell?

Customer: replied 4 years ago.
No electrical burning smell anywhere.

Expert:  Billy replied 4 years ago.

 

The upper circuit board is the main suspect...to be sure, check edge connector wiring on the schematic to the furnace....locate 24v feed from edge connector to the inducer relay.

 

24v present= bad inducer board.

No 24v = bad main board.

Customer: replied 4 years ago.
I will do that now.

Do you know what I ask for when searching for replacement boards? Is there a part number or just 'main board' for Payne model # XXXXX ?
Expert:  Billy replied 4 years ago.
Billy, HVAC Technician
Category: HVAC
Satisfied Customers: 19947
Experience: Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
Billy and 3 other HVAC Specialists are ready to help you
Customer: replied 4 years ago.
Okay. Replaced blower board but that didn't fix it.

The only low voltage line coming directly off the blower board is #6 Orange, going thru what I've been calling the cutoff switch, read 1.75v on both sides of that switch, therefore 1.75v going into the inducer board. And as you said: No 24v = bad main board, I took a chance and replaced the main board.

Any ideas, without replacing components 1 by 1 until it starts working? That would get awfully expensive!

Attached is a pic of my schematic.graphic
Expert:  Billy replied 4 years ago.

 

I see your version has the 3 wire pilot...

 

for sake of eliminating ......hit the side of the pilot assembly to make sure it returned to normally closed. I will be online off and on today to see how it is going.

Customer: replied 4 years ago.
It's closed. I have continuity between G & Y on the pilot.

It seems to me that it must have been a high voltage component that shorted early Sat morning - it had to be to cause a smoke detector to go off. What high voltage components would be most likely?
Expert:  Billy replied 4 years ago.

 

our blower motor runs with R and G so that is good....can you get 120 v to the inducer motor for test?

Customer: replied 4 years ago.
Put 120v to inducer motor - tested okay.

Do you know what resistance I should get across various leads on the inducer board?
Customer: replied 4 years ago.
what resistance I should get across various leads on the inducer board?
Expert:  Billy replied 4 years ago.

 

I do not have resistance values....but the 3 wires going to pressure switch work by running 24v to switch an out on nc...then on start up 24v should appear on n.o.

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