Furnace blowing cold air only

furnaces suck alot of battery power. How many and what group of battery(ies) do you have?

Well it seems like it needs more Volts than the 10.5 it says it needs to ignite.
This morning at 11V it would not ignite.
So I'm charging it back up to 12.5 and we will see then I guess.

Glad you got it working!

RollandBC wrote:
Problem solved
Thanks everyone for the help, I learned a lot about how the furnace works.
It's running hot!

Low DC Voltage....fan could NOT come up to rated speed to generate enough airflow to make up Sail Switch

Problem solved
Thanks everyone for the help, I learned a lot about how the furnace works.
It's running hot!

So I pulled the board ,blew the dust off
reinstalled
all connections look good
just topping up the 12V trailer batteries they were reading just over 10.2

White and Blue wires sticking thru the motor cover go to sail switch
Blue is 12VDC+ from thermosyat to timed delay relay & sail switch
White is 12VDC+ from Sail Switch when is closes....goes to circuit board

White wire at connector should have 12VDC+ IF sail switch closes/works with fan ON
Yellow is Ground wire

Got DC Voltage at white/yellow
Then check for DC Voltage at RED & Yellow (RED is DC + to gas valve solenoids)




Battery Voltage
Drawing voltage below 12.1V can cause damage
You drawing them down to 10.2.....they ARE Damaged

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Yes that photo is not mine just 1 the same looking
I will try that

Here is a thought:
Remove the circuit board from furnace. Then re-install and try again.
Didn't work, look at your water heater circuit board and see if they are the same. Quite often they are. Swap out board with furnace and try again.
n your photo I see the circuit board connector hanging loose. You do have a circuit board?