Gas and Oil Home Heating Furnaces - no heat from furnace

I have a forced air unit made by Rheem(I believe or Lennox they are both on the furnace). The system does not seem to turn on even though the theromstat is calling for heat. I have a tech working on it but he doesn't seem to know what the problem is and he has changed the board and checked the grounds. The bower will come on for 3 seconds and then turn off....anyone have any idea. Thanks!

Hi,
First,I don't want to overide the tech,so these are only suggestions,he's there,I'm not.

Could be bad fan relay,capacitor,loose wiring connection,T-Stat,Breaker/fuse.I would look at wiring schematic and trace circuit (High and Low voltage ) from Power source to the Blower through all controls until problem is located.

I would NOT change ANY parts until problem is located.Parts changing can get expensive and Electrical Parts are non-returnable once installed.You can by-pass/jumper each component/control (switch-relay) to determine if part is bad.If bad, you then need to determine why,
so as not to have repeat failure.I would first check each control for correct voltage (High and Low ) and if not correct,then see if unit starts with control jumpered.

Write back if more help/info needed. Take Care.

CoolBreeze

Place tstat to fan on and run blower for 5 minutes.Try it several times for 5 minutes at a shot.If your blower responds every time the blower motor is okay.If this does not correct the blower problem,remove tstat,take red wire and green wire hook them together.This will give you a direct path of 24 volts to your fan relay,and thus your blower motor.PDF

PDF,

Just received e-mail from gossamer725 that the tech apparently feels it's now a faulty ignitor. Stated the tech said he checked it earlier and it was supposedly fine.You thinking what I'm thinking?

CoolBreeze

"GROUND FROM FURNACE TO BREAKER BOX MUST BE OF 1 WIRE AND UNINTERRUPTED AND CLEAN" if not solid state board will not function properly.I still do not know if g725 has ever gotten ignition.PDF

PDF,

I don't know if they got ignition either.If I get another e-mail,I'll post on here.The tech said it was a bad circuit board and changed it,unit still didn't work so he then said it was a faulty ignitor which he had previously checked and said was good.Take Care.

CoolBreeze

Hey PDF,

Received e-mail that Ignitor was replaced Friday and so far,they have ignition and it's working.Take Care.

CoolBreeze

Thanks for the update.I sure hope customer kept old board.I really hope the company that did the work will adjust bill,both labor and parts cost.PDF