Suburban NT-30SP Furnace won't start

[OldEdBrady]

Suburban NT-30SP furnace.  In the past, it would turn on, fan start, wait a bit (seconds) and then it would light.  Fan doesn't start, so neither does burner.  Have NO idea what to do.

[ClydesdaleKevin]

My furnace problem a year ago was all bad connections and lots of dirt build up.  Once everything was cleaned and all the connections cleaned up, she's been working like a champ ever since.


Kev

[Oz]

Ed, do you have the manual for it? 
It's in the Member Area > Manuals & Diagrams >  Furnaces > Suburban.

[DaveVA78Chieftain]

Seems to be that time of year 

You have a DSI model furnace with intregal fan control relay:  http://www.classicwinnebagos.com/forum/index.php?topic=2640.msg5117#msg5117

NT-30SP - http://www.vintagetrailersupply.com/v/vspfiles/assets/images/inst%20204555%20date%20code%2012-23-08%20rev%20b%20nt30%20and%2034sp.pdf

Fan is directly controlled by control board so:

Is 12VDC supply breaker to furnace ON?
Have you installed a battery operated Thermostat?  (i.e battery OK?)
Is local power switch (on furnace iteself) ON?
Do you have good cable connections at furnace and thermostat?
If all that is OK then either the fan motor or the control board is defective.

You said fan is not working so:
Thermostat is like a switch.  When ON it supplies 12VDC (from your RV power panel) to the Local Power Switch on the Furnace.  If that switch is ON, it provides 12VDC to the control board.  Control board says Yeah I got Power so it turns the fan motor ON.
The sail switch, ignition and gas valve actions are after that point so they are not involved.  Fan has to start before they are looked at.

Dave

[vincewarde]

If the fan won't spin, it could be a wasp's nest in the blower.  Happened to me :-)

[Froggy1936]

Yep mud wasps are very likely Had a fan on my stove exaust hood that would not run Found a 2 lb wasp nest blocking blade Frank