Time to Troubleshoot the furnace

Old-Biscuit wrote:

westend wrote:
Chris Bryant, a member of this Forum has libraries of appliance owners and service manuals for download on his Website. The service manuals for furnaces have a trouble shooting chart and descriptions of the locations for electrical diagnosing.
Thanks Chris!!

BTW, the blower needs to operate before the gas valve will open. There is a sail switch that interrupts current to the gas valve. If the sail switch doesn't move or close--no gas to igniter and burner.

FAN is NOT coming on...........so issue is with power to fan motor or circuit board

Should be something like this wiring scheme

Ok, so what wires do I test?

westend wrote:
Chris Bryant, a member of this Forum has libraries of appliance owners and service manuals for download on his Website. The service manuals for furnaces have a trouble shooting chart and descriptions of the locations for electrical diagnosing.
Thanks Chris!!

BTW, the blower needs to operate before the gas valve will open. There is a sail switch that interrupts current to the gas valve. If the sail switch doesn't move or close--no gas to igniter and burner.

Yes, I have read that, but it for a novice like me, it's not enough info. For example, it says to check the voltage at the furnace. Great, but it does't tell me how. :/

westend wrote:
Chris Bryant, a member of this Forum has libraries of appliance owners and service manuals for download on his Website. The service manuals for furnaces have a trouble shooting chart and descriptions of the locations for electrical diagnosing.
Thanks Chris!!

BTW, the blower needs to operate before the gas valve will open. There is a sail switch that interrupts current to the gas valve. If the sail switch doesn't move or close--no gas to igniter and burner.

FAN is NOT coming on...........so issue is with power to fan motor or circuit board

Should be something like this wiring scheme

Toddupton wrote:
Bee hive in the blower maybe. They love the smell of gas. Do you have any screens on the outside intake or vent?

Looking into the exhaust pipe, I don't see any obstructions. I can also reach in and turn the fan with my finger, and it doesn't feel like it's obstructed either.

I want to put my multimeter to good use, but I don't know what wires to be testing.

Chris Bryant, a member of this Forum has libraries of appliance owners and service manuals for download on his Website. The service manuals for furnaces have a trouble shooting chart and descriptions of the locations for electrical diagnosing.
Thanks Chris!!

BTW, the blower needs to operate before the gas valve will open. There is a sail switch that interrupts current to the gas valve. If the sail switch doesn't move or close--no gas to igniter and burner.

donn0128 wrote:
Propane?
12VDC?
Demand?
Those are the three things you need to have to have heat!

I have propane, but that doesn't matter since it won't try to light until after the blower starts.

My batteries and converter are brand new, fully charged, and I'm plugged in. I don't know how to test if the furnace is getting 12v.

It's cool enough that there should be demand. Especially since when I tested it, it was a mid summer morning. It's colder than that right now.

DC Voltage comes from a 'fused' circuit at DC Dist. Panel
Goes to:
t-stat and to an ON/OFF switch (local on frame of furnace).
From ON/OFF switch it goes to circuit board...that is ahy you have a GREEN light. Board has power.

From t-stat it goes to:
limit switch and sail switch where it stops until fan comes on and makes u sail switch
it also goes to circuit board for the 'timed delay' function (starts fan which makes up sail switch allowing voltage to go back to board....time delay then allows voltage to gas valve & sparker)

Sounds like issue is with timed delay circuit on board or with 4 wire connector on board.

When T-stat makes up (CLICK) DC voltage should be on:
RED wire from board to fan motor
BLUE wire in 4 wire connector to board
WHITE/BLUE (could be either) wire from t-stat to limit switch/to sail switch (but not on white wire from sail switch to 4 wire connector until fan runs)

Nothing gonna happen til the blower runs....

Bee hive in the blower maybe. They love the smell of gas. Do you have any screens on the outside intake or vent?

Propane?
12VDC?
Demand?
Those are the three things you need to have to have heat!