'79 Suburban NT-30 furnace - Repair or replace?

[blickcd]

I've never had much use for my furnace until now, and it's pretty unreliable.

From dead cold when you turn on the thermostat the blower comes on, the burner will fire up and run normally, but at some point overnight the burner will not light so the ignition locks out and the blower runs continuously. In the morning when I check on the trailer (not spending the night out there yet) what sounds like the blower motor bearings, which were quiet on start-up, now have a bit of a squeak to them.

Could be a problem with the ignition, or a bad solder joint on the board that opens up once the furnace runs a bit and heats up. Could also be that the motor bearings start dragging once its been running a while and can't turn fast enough to operate the sail switch. I assume voltage to the furnace is fine since the trailer is plugged into shore power and the furnace initially fires up.

This furnace appears to be original one from 1979. I could probably replace the board and the blower motor and anything else wrong with it, but given the age of the furnace should I spare myself the aggravation and just install a new one?

If anyone has replaced their old NT-30, I understand that the new models are a bit shorter so you have to mount them on a piece of plywood in order to line up with the vent holes on the body. I'd just like some confirmation on that.

Thanks,
Christopher

[Wazbro]

Well from what others have said by the time you replace enough to make the old one reliable it would be cheaper to replace it. Also a new one uses less power.