Trane DH1B040A9241C Series, Service Facts

UH1-DH1-SF-1L

Service Facts

17

2 Flash Fault LED

Cycle power to 

furnace and call 

for heat 

Does gas 

ignite?

YES

NO

Is outlet gas 

pressure 

~3.5"WC (NG)

~11.0"WC (LP)

YES

Do all burners 

ignite within 5 

seconds?

Check igniter 

position and 

correct if needed. 

Check operation

Adjust manifold gas 

pressure

 to ~3.5"WC (NG)

~11.0"WC (LP)

Check operation

NO

Clean and align 

burners correctly.

Check operation

NO

YES

Measure flame 

current. Is flame 

current less than 1 

micro-amp?

(3-4 ua = Normal)

YES

Is flame sensor 

located 

correctly? 

Replace flame 
sensor. Check 

operation

YES

Correct and check 

operation

NO

Flame sensor is 

good

NO

Is minimum 

outlet gas 

manifold 

pressure 

maintained?

Does inlet gas 

pressure drop 

more than 2" 

WC

NO

Correct inlet gas 

pressure

Check operation

Replace Gas Valve

Check operation

YES

Disconnect electrical 

power to furnace.

 Connect manometer 
to oulet gas pressure 

connector

NO

Cycle power to 

furnace and call 

for heat

YES

DEFINITION 

RETRY Lock Out = 3 unsuccessful tries for 
ignition within a single call for heat

Flame has never been sensed

RECYCLE Lock Out = 10 recycles within a 
single call for heat. 

Flame is sensed & then lost

For CORRECT 
positioning of the 
igniter and flame 
sensor, see figure 
on next page

Disconnect electrical 

power to furnace.

 Connect manometer 

to inlet gas pressure 

connector

Is inlet gas pressure 

above 14" WC or less than 

nameplate minimum ?

NO

Correct inlet gas 

pressure

Check operation

YES

Downflow model 

*DH1D110A960 only:

Outlet gas pressure 

~4.5"WC (NG)

~11"WC (LP)

Downflow model 

*DH1B065A942 only:

Outlet gas pressure

~3.0"WC (NG)

~9.5"WC (LP)

Downflow model 

*DH1D110A960 only:

Adjust manifold gas pressure 

to ~4.5"WC (NG)

~11"WC (LP)

Downflow model 

*DH1B065A942 only:

Outlet gas pressure

~3.0"WC (NG)

~9.5"WC (LP)

Check operation

NO