Suburban furnace wont lite?

[Dsrtrider]

My Suburban SF42 wont lite. Blower comes on for about 30 seconds then shuts off. Burner doesnt lite. Ckd sail switch has continuity but no power going to it? Ckd limit switch it also has continuity thru it. Is the board bad? Is there a way to test the board?

[Skip426]

Are you testing for power at the sail switch , when the fan is running ?

Some RV parts stores have the equipment to bench test the control boards, for furnaces and water heaters, you will have to phone the shops in your area.

[shiggs68]

Just jumper across the sail switch to see if the call for heat process proceeds to burner ignition. Since the sail switch signals the board, it may not have a 12v level across it.


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[Wild Card]

When checking for voltage at sail switch...you will see 0 volts if it's closed, if it's open you should see 12volts. That's any relay or switch of any voltage. Why...you are only reading through that one leg. Kinda like putting your meter on the same wire with the leads 2 inches apart(closed switch)...now cut that wire between leads and you'll read voltage(open switch).

I would check for obstruction in the intake and exhaust before I jump the sail switch. Just suck it out with a shop vac you should get no resistance. If you have minimal airflow through chamber and it lights off you may get a pretty violent light off. Beware.

If your not getting power to any terminal to ground on the sail switch while trying to start you need to go back to the next device in line. If the module is not sending power out then it's the module.

[Dsrtrider]

I have no power at either leg of sail switch when blower is running.