Hi,I have a aire flow furnace,burners come on but fan doesn't.The motor is not stuck and turns freely.Im asumming the control board is bad or a limit switch.any ideas please?

Don't assume test your parts with an ohm meter. Or have them tested by a professional.

If it were a limit switch, the burners would not come on. You need to measure voltage coming out of the heating speed blower terminal on the board. After the burners have been on for a minute or less, you should get 120 volts between that terminal and neutral. If you do not, the board is the source of the trouble.

If it were a limit switch, the burners would not come on. You need to measure voltage coming out of the heating speed blower terminal on the board. After the burners have been on for a minute or less, you should get 120 volts between that terminal and neutral. If you do not, the board is the source of the trouble.
Thanks for response.Do you know what terminal to check?the wirig diagram is missing on my friends unit.I have knowledge of heatig and air,but hard to diagnois without schematic.Im old school a/c heating guy,never had to deal with these control boards.

Thanks for response.Do you know what terminal to check?the wirig diagram is missing on my friends unit.I have knowledge of heatig and air,but hard to diagnois without schematic.Im old school a/c heating guy,never had to deal with these control boards.

What's the model number?

What's the model number?


m/n : AF80MPA100B4

Here's a link to a picture of the board. The heating speed fan terminal is in the lower right corner. Once the flame has been on for 30-45 seconds, you should get 120v between that terminal & a neutral. You will probably have to hold the push button door switch in to get anything to happen.

Here's a link to a picture of the board. The heating speed fan terminal is in the lower right corner. Once the flame has been on for 30-45 seconds, you should get 120v between that terminal & a neutral. You will probably have to hold the push button door switch in to get anything to happen.


Thanks for info.didnt see a link for control board.but understand what you said I'll check board.
Thanks

Thanks for info.didnt see a link for control board.but understand what you said I'll check board.
Thanks
Having trouble finding the correct term.if you have diag.it will be helpful
Thanks

Oops, guess I forgot the link. Let's try again. http://www.hvacpartsplus.com/images/detailed/0/80M271351449129508d7a298095c.jpg

Oops, guess I forgot the link. Let's try again. http://www.hvacpartsplus.com/images/detailed/0/80M271351449129508d7a298095c.jpg

OK got it thanks,so it's the very bottom term lower right.is there a colored wire coming off it,or any labeling.on term?

The terminal is labeled "heat".

The terminal is labeled "heat".
OK,My friend who knows nothing about Heaters.replace the thehttps://youtu.be/H8Q83DPZy6Erm.He put a honeywell Heat and cool therm on his heater.he hooked the red wire from control board to red on therm,and hooked the white wire from control board to green term on therm.He said it worked like that,but he had to turn it off and on by therm switch every time. I hooked the what wire from control board,to what term on therm.so it will now go on by sliding the temp lever to above ambient temp,with therm when set to heat and auto fan and all the way up on temp setting.combustion fan comes on and then burners.After about 40 secs,I hear a click fom control board,but no fan comes on.I tested heat term on control board no volt coming out at that time.I pulled wire off heat term and supplied 110 volts to fan, then it came on.
Do you think the way he had it hooked up on therm,(white wire to green term on therm) it could have blew out control board for indoor fan?
Does it sound like bad control board?


The terminal is labeled "heat".
OK,My friend who knows nothing about Heaters.replace the thehttps://youtu.be/H8Q83DPZy6Erm.He put a honeywell Heat and cool therm on his heater.he hooked the red wire from control board to red on therm,and hooked the white wire from control board to green term on therm.He said it worked like that,but he had to turn it off and on by therm switch every time. I hooked the what wire from control board,to what term on therm.so it will now go on by sliding the temp lever to above ambient temp,with therm when set to heat and auto fan and all the way up on temp setting.combustion fan comes on and then burners.After about 40 secs,I hear a click fom control board,but no fan comes on.I tested heat term on control board no volt coming out at that time.I pulled wire off heat term and supplied 110 volts to fan, then it came on.
Do you think the way he had it hooked up on therm,(white wire to green term on therm) it could have blew out control board for indoor fan?
Does it sound like bad control board?

I wouldn't think that would blow the board but stranger things have happened & yes it does sound like a bad board.

I wouldn't think that would blow the board but stranger things have happened & yes it does sound like a bad board.
Thanks for your help, that's where I'll start

Keep me up to speed on progress.