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BillyHvac
BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22385
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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I have a trance xl80 that won't ignite. Small fan blows,

Customer Question

I have a trance xl80 that won't ignite. Small fan blows, igniter glows read but has value doesn't open. I checked that gas is flowing on other appliances. I get the 2 flashes flash code. This has happened before, a year ago and then just two weeks ago. Each time unplugging the three position plug on the gas valve worked to get everything going but won't now
Submitted: 4 months ago.
Category: HVAC
Expert:  BillyHvac replied 4 months ago.

Hello,

Unfortunately this is a fairly common fault.

The board is flashing ignition failure because it thinks it has sent power to the ignitor and then to the valve, but there is no flame.

It ia always one of 2 items....it is the board thinking it sent 24v to gas valve but actually did not...or the board did send 24v to valve but the valve is bad.

It is more commonly the valve on this unit but the 24v test tells for sure.

Valve gets 24v but doesnt open = valve

No 24v =bad board

Billy

Customer: replied 4 months ago.
Which wires do I need to check to determine if the 24v is being sent
Expert:  BillyHvac replied 4 months ago.

do you have the TUD or TDD?

Customer: replied 4 months ago.
Sorry not sure what either is
Expert:  BillyHvac replied 4 months ago.

the model number...the XL is just a series...there is a model num ber on a tag inside the furnace

Customer: replied 4 months ago.
Tdd
Expert:  BillyHvac replied 4 months ago.

Thank you...then 2 of the 3 wires to valve are red and black?

Customer: replied 4 months ago.
I've got a red and gray coming from the board and a brown coming from pressure sensor
Expert:  BillyHvac replied 4 months ago.

Ok so your unit is older than 5yrs then?

Customer: replied 4 months ago.
Expert:  BillyHvac replied 4 months ago.

Ok lets back track a little...do you have 2 pressure switches?

I would like to do a test if you game for a hands on test?

Customer: replied 4 months ago.
there are two sensors. I'll do everything I can to get the heat on.... dinner party starting in two hours...
Expert:  BillyHvac replied 4 months ago.

ok turn power off and take the wires off the pressure switch. Shoild be 2 browns on one side and a orange on the other..correct?

Expert:  BillyHvac replied 4 months ago.

this will move quicker now that I know you have a 2 stage..

Customer: replied 4 months ago.
Just on the one sensor with the two brown and one orange? It's marked P01 HI
Expert:  BillyHvac replied 4 months ago.

we want to take the wires off

start furnace

And AFTER the exhaust fan starts connect the wires direct together...a short wire shaped in a U works well for sticking in the wire end connectors.

Then tell me code..

Customer: replied 4 months ago.
Working on that now
Expert:  BillyHvac replied 4 months ago.

standing by

Customer: replied 4 months ago.
it hasn't behaved any different and code is still 2 flashes, no flame
Expert:  BillyHvac replied 4 months ago.

thank you...now put those wires back...and do the same thing to the other pressure switch

Customer: replied 4 months ago.
On it
Customer: replied 4 months ago.
far nothing new. Just waiting it to go through all the cycles
Expert:  BillyHvac replied 4 months ago.

understood....at any time has the gas valve clicked?

Customer: replied 4 months ago.
I've only really heard clicks from the board. I think I can hear a small humm at the value for a few seconds. Just got the same code
Expert:  BillyHvac replied 4 months ago.

Thank you.

Well we took the entire pressure circuit out of the picture...which puts us back to the valve issue.

You can unplug the 3 wire plug and put meter lead black to a ground and meter lead red to the black during ignition...you will only see voltage for 3 seconds...then test the gray and brown the same way...during the glow it will be energized for 3 seconds..

no 24 on any wires = board

24 on any wire = bad valve

Customer: replied 4 months ago.
I only have red, light gray and brown. Set the meter to 200 D.C.?
Customer: replied 4 months ago.
I have 20 then 200
Expert:  BillyHvac replied 4 months ago.

we want ac volts~

Customer: replied 4 months ago.
K
Customer: replied 4 months ago.
Got over 24v on the red wire
Expert:  BillyHvac replied 4 months ago.

thank you..you just confirmed bad gas valve.

Customer: replied 4 months ago.
Dang. You wouldn't happen to have the PN would you?
Customer: replied 4 months ago.
It did this just last weekend and started working fine after I messed with it. Any tricks to limp through tonight
Expert:  BillyHvac replied 4 months ago.

I have wedged tooth picks...tapped with hammer...depends if the there is a connection bad, poor solenoid etc.

See here