Trane xb80

[tommyt37]

Hello folks! Yesterday after coming home from work I noticed the house was a bit chilly. Noticed air was being blown but it was only cold air.

The following is what I know and what I have looked at.

1) Heat is commanded vent motor fires up. After about 6 seconds vent motor shuts off and main fan blower kicks on. No flame, no ignition...

2) Error LED flashes 6 times. Supposed to mean 115VAC reveresed polarity or bad ground.

3) I checked all powerI have 120VAC.. getting to the circuit board. I have 120VAC on Primary of transformer and 27VAC on secondary being fed to CB.

4) I have no voltage ever getting sent to Gas valve or ignitor. Have clean filter shorted out safety switched one at a time same results.

This one is bugging me I am not sure what the cause would be... I am thinking it may be the Circuit board but I don't know. About ready to give in and call HVAC tech but any other advice would be welcome.

Regards,
Tom Spokane, WA

[paul52446m]

Hello folks! Yesterday after coming home from work I noticed the house was a bit chilly. Noticed air was being blown but it was only cold air.

The following is what I know and what I have looked at.

1) Heat is commanded vent motor fires up. After about 6 seconds vent motor shuts off and main fan blower kicks on. No flame, no ignition...

2) Error LED flashes 6 times. Supposed to mean 115VAC reversed polarity or bad ground.

3) I checked all powerI have 120VAC.. getting to the circuit board. I have 120VAC on Primary of transformer and 27VAC on secondary being fed to CB.

4) I have no voltage ever getting sent to Gas valve or ignitor. Have clean filter shorted out safety switched one at a time same results.

This one is bugging me I am not sure what the cause would be... I am thinking it may be the Circuit board but I don't know. About ready to give in and call HVAC tech but any other advice would be welcome.

Regards,
Tom Spokane, WA

Have you done anything that would have reversed the polarity? On the board test from the hot black to cabinet ground and see if you have 120 volt. If you don't get the 120 then you don't have a good earth ground. The furnace has to have a good earth ground to work. Does your pressure switches have 2 or 3 wires on them?
Do you have a bare ground in the wiring going to the furnace? Test between your black hot to the bare ground to see if you get a full 120 volts. Has any one have the wires off the board ? its real easy the get the hot and ground switched on the board. If the limit switch in open it will cause this problem. Check it out and let me know. later Paul

[tommyt37]

"Have you done anything that would have reversed the polarity?"

Nope not a thing that what was strange about error. So I figured bad ground or 120 supply but so far nothing.

"On the board test from the hot black to cabinet ground and see if you have 120 volt."

I did this from board to cabinet ground I got 120. From the furnace disconect switch that supplies ground got 120 and from panal inter-lock switch got 120.

"Does your pressure switches have 2 or 3 wires on them?"

It is a honeywell pressure switch that has 2 yellow wires connected to one terminal and a red connected to the positive terminal. Red supplied power from board yellows i think are part of the error loop... shows if switch is open or closed along with all the other safety switches.

"Has any one have the wires off the board ?"
I have lifted all wires and reseated with no luck.

I still have not checked ground from main breaker box in garage but I figured if I got good ground to it in basement then why bother?

"If the limit switch in open it will cause this problem"

Limit switch I have the following switches
1)thermal cut out a and b
2)pressure switch
3)Flame rool out switch
4)door switch

for tco's i pulled yellow wires and shorted and stayed the same.

with pressure switch air hose pulled the vent motor just stayed on... my failure is vent motor come on for a bit kicks off then main blower kicks on with no heat.

why no voltage to gas valve?

thanks or your advice and help... :-) kinda like having another guy around the house lol
tom

[paul52446m]

"Have you done anything that would have reversed the polarity?"

Nope not a thing that what was strange about error. So I figured bad ground or 120 supply but so far nothing.

"On the board test from the hot black to cabinet ground and see if you have 120 volt."

I did this from board to cabinet ground I got 120. From the furnace disconect switch that supplies ground got 120 and from panal inter-lock switch got 120.

"Does your pressure switches have 2 or 3 wires on them?"

It is a honeywell pressure switch that has 2 yellow wires connected to one terminal and a red connected to the positive terminal. Red supplied power from board yellows i think are part of the error loop... shows if switch is open or closed along with all the other safety switches.

"Has any one have the wires off the board ?"
I have lifted all wires and reseated with no luck.

I still have not checked ground from main breaker box in garage but I figured if I got good ground to it in basement then why bother?

"If the limit switch in open it will cause this problem"

Limit switch I have the following switches
1)thermal cut out a and b
2)pressure switch
3)Flame rool out switch
4)door switch

for tco's i pulled yellow wires and shorted and stayed the same.

with pressure switch air hose pulled the vent motor just stayed on... my failure is vent motor come on for a bit kicks off then main blower kicks on with no heat.

why no voltage to gas valve?

thanks or your advice and help... :-) kinda like having another guy around the house lol
tom

When checking for grounds, there are two grounds to check.
one is on the board test the black to white, the other is test from black to the bare ground, both should give you 120 volts. If you have checked all roll out, limit. and pressure switch, then it could be your board.. You will not get power to gas valve until it goes through all these switches and back to the board. then you will get either spark or glow bar, which ever you have. Then the last thing you get is about 6 seconds of 24 volt power to gas valve.
Later Paul