[Mickey12]

I can't reset the lockout. Gas valve does not open or click, Igniter does not light or receive power. Nothing happens. Circuit board has power & air-conditioning mode works implying thermostat OK. Nat gas furnace will not do anything. Igniter measures 70 ohms. The only way I can get diagnostic light to reset is to switch to AC then go back to heat where I get an immediate lockout without anything happening in the furnace sequence of lighting off. Looks to me like the circuit board is bad but I don't if something else could be causing an immediate lockout with inability to reset.
Can anyone help me? I am stumped at this point and don't want to buy a circuit board without some verification. Thanks for anyone's help. Mickey

 

[JJboy]

Check if any rollout, limit switch are open. If all safety switches are ok sounds like a bad control board.

Sent from my iPhone using DIY Forum

 

[Mickey12]

Total lockout, 2 flashes, no gas, no ignition.

Thanks JJBoy! The Thermostat is applying power. Both limit switches OK. The 2 microswitches attached to the air pressure lines are OK except one stays closed & one open sensing fan air I guess. Zero voltage read between green & white 120VAC input wires. I don't know what else to check. The darn circuit board will not reset and LED gives 2 flashes for lockout, and it means in my case TOTAL LOCKOUT. Could you give me an idea how to go about buying a board to try? The only place near me just about doubles the price unless you are a HVAC company. Do I need to replace the part of the board that says "White-Rodgers" on it or just the green circuit board. Thanks again for helping.

 

[Mickey12]

Trane XV80 Hard Lockout,2flashes, unable to reset.

Checked for thermostat voltage to Red & W1, checked limit switches, checked for 0 volts between green & white line input voltage, checked for loose connections. Red LED continues to flash 2 times after power recycled for reset.
Gas valve & igniter receive no power. I don't know what else to check. Does anyone have any more ideas to prove circuit board is bad?

My Trane furnace model is XV80, model # TUD100R9V5H6. If circuit board, do I replace the white box labeled "White-Rodgers, Model 50A51-507" or just the small green circuit board labeled "American Standard 21C148501P01?

I appreciate any more help you could give me including where to buy the board.
Thanks! Mickey

 

[JJboy]

Jumper R and W an close the door safety switch. If all safety switches are working the Draft motor then starts. When the pressure switch close the hot surface igniter will glow. After that, the gas valve open and all the burners light, the flame sensor make the burners keeping on.....after that, the blower motor starts.....

Check what flash code error is this. You should have a code label on the cover.

 

[Mickey12]

Trane XV80 Hard Lockout,2flashes, unable to reset.

JJboy, Thanks for the help. I was told there are 5 safety or interlocks. I can only find 2 for sure, the limit switches. The only other 3 that might be keeping the circuit board in lock out are the igniter, and 2 pressure switches that I can see. Is that correct?

The igniter measured 70 ohms. With fan off, the right air pressure switch is closed completing the circuit. The left air pressure switch is open which is strange. Perhaps it closes with air pressure. Could this air pressure switch be causing lockout?

I jump R to W1 or W2 and I get nothing but the Red LED keeps blinking twice.

Something is locking out this board from starting the sequence. Thanks again!
Mickey

 

[JJboy]

" With fan off, the right air pressure switch is closed completing the circuit. The left air pressure switch is open which is strange. Perhaps it closes with air pressure.

I jump R to W1 or W2 and I get nothing but the Red LED keeps blinking twice."

Does not make sense. If the furnace is locked you shouldn't have the fan on. No air pressure at all.

Turn OFF the furnace. These 2 pressure swtich should be open (infinity resistence 0L) all the other safety should be close ( 0 ohms).

If you have this situation and the control board is ok the small fan motor should turn on when you jump R-W.

You also should have some resistence on the 2 fan motor wires. If you get 0 ohms or OL ohms the fan motor is bad.

 

[Mickey12]

Trane XV80 Hard Lockout,2flashes, unable to reset.

" With fan off, the right air pressure switch is closed completing the circuit. The left air pressure switch is open which is strange. Perhaps it closes with air pressure. I TOLD YOU WRONG-BOTH AIR PRESSURE SWITCHES ARE OPEN. ON MY OTHER FURNACE THAT WORKS, THEY ARE BOTH OPEN, SO THESE ARE NOT THE PROBLEM.

I jump R to W1 or W2 and I get nothing but the Red LED keeps blinking twice."

Does not make sense. If the furnace is locked you shouldn't have the fan on. No air pressure at all. THE FAN IS NOT ON & WILL ONLY WORK IN COOL MODE. CIRCUIT BOARD WILL ONLY RESET IF BREAKER CYCLED OFF THEN ON IN THE COOL MODE. SWITCHING TO HEAT CAUSES LOCKOUT AFTER ABOUT 5 SECONDS.

Turn OFF the furnace. These 2 pressure swtich should be open (infinity resistence 0L) all the other safety should be close ( 0 ohms). THEY ARE BOTH OPEN.

If you have this situation and the control board is ok the small fan motor should turn on when you jump R-W. WITH A LOCKOUT, SHOULD'T THE SMALL FAN MOTOR BE LOCKED OUT WHEN R-W IS JUMPED?

IN ANY CASE JUMPING IT WILL NOT MAKE IT WORK. HOWEVER IT WILL WORK FOR 5 SECONDS WHEN COMING FROM COOL TO HEAT, FOLLOWED BY A LOCKOUT WITH 2 FLASHES.

I CHECKED ALL VOLTAGES AND THEY ARE NORMAL. IT SEEMS LIKE SOMETHING IS LOCKING THE CIRCUIT BOARD OUT BEFORE ANY START SEQUENCE IS INITIATED LIKE THE BOARD IS SENSING SOMETHING WRONG, OPEN, OR NOT IN TOLERANCE.

COULD THE IGNITOR MEASURING 70 OHMS BE OUT OF LIMITS ENOUGH TO CAUSE A LOCKOUT? THANKS AGAIN FOR YOUR HELP.