Sf-30q blower motor hesistates, takes a few "attempts" to get started.

[lucass]

Hello, Lucas here.

I've got a trailer with this furnace. Suburban sf30q, It was not functioning at all, until I replaced the control board. Annnd then It still didn't work. So I tested the limit switch for continuity, and after successfully having that, I (once again) pulled the blower fan cover off and cleaned(and eventually replaced, to seemingly no effect) the sail switch. Somehow I got the heater working, but the blower fan on startup takes a few attempts at starting, and then slowly gets up to speed and my heater seems to function fine afterwards. It did not ever used to hesitate. And until I tinkered around, wouldn't start at all, it used to just click once, then 30 seconds later click again and be done.

My only guess is it's the blower motor going out? Which isn't cheep to fix but I'll buy the motor if that's the failure.

 

[Mark_K5LXP]

The general troubleshooting procedure is to verify the voltage being supplied to the motor, at the motor. It's possible a bad connection or supply issue can cause the voltage to be low and that would cause the motor to start and run slowly. As a sanity check you can power the motor directly to eliminate the variables of the control board or other connections. If it is running improperly with sufficient voltage, your options are limited as most small motors are not really meant to be fixed. I'll usually try because sometimes it's something stupid like a crappy bearing or stuck brush, if you can get at them. But first go/no-go the supply to the motor before going down that path.

Mark B.
Albuquerque, NM

 

[lucass]

The general troubleshooting procedure is to verify the voltage being supplied to the motor, at the motor. It's possible a bad connection or supply issue can cause the voltage to be low and that would cause the motor to start and run slowly. As a sanity check you can power the motor directly to eliminate the variables of the control board or other connections. If it is running improperly with sufficient voltage, your options are limited as most small motors are not really meant to be fixed. I'll usually try because sometimes it's something stupid like a crappy bearing or stuck brush, if you can get at them. But first go/no-go the supply to the motor before going down that path.

Mark B.
Albuquerque, NM

Thank you, I will attempt to do this tomorrow. If it continues with the issue.

 

[Onyrlef]

A new control board with a faulty capacitor shouldn't be ruled out. New, but faulty control boards are not uncommon. Yours sounds suspiciously like a start capacitor issue.

 

[Mark_K5LXP]

12V DC motors don't have start capacitors. Documentation doesn't show a schematic of the control module but I would bet the control element is a relay.

Mark B.
Albuquerque, NM

 

[Onyrlef]

That cylindrical thing on the control board with the wire running from it ain’t a paper weight, it’s an intermittent capacitor.

 

[Mark_K5LXP]

12VDC motors don't have start capacitors.

Mark B.
Albuquerque, NM

 

[lucass]

Well, gosh darn it. It's working perfectly, as soon as I made the post. Fires up perfectly first try. Ignites and starts heating aswell. I'm not one to fix something not actively broken. So I appreciate the help, and if it starts up again with the problems I'll continue trying to diagnose.

 

[Onyrlef]

Well, gosh darn it. It's working perfectly, as soon as I made the post. Fires up perfectly first try. Ignites and starts heating aswell. I'm not one to fix something not actively broken. So I appreciate the help, and if it starts up again with the problems I'll continue trying to diagnose.

Not trying to be a debbie downer, but I've had the same type issues. The furnace would work like an eight day clock and then like voodoo just decide to not work for a day or so and then just like thst start working fine again. That for me was a circuit board issue and what it seemed to me pointed in your case to a capacitor issue on your circuit board. Otherwise, all you can do is let it ride until or if it doesn't. I carry spares on board for the big 5 most likely to fail parts, ignitor, sensor, limit sw., sail switch and circuit board.
As circuit boards are notoriously unreliable, even out of the box, I like to swap the new board with the old working board as soon as I get the new board. Better to learn if it's a bad board now than later.

 

[lucass]

Not trying to be a debbie downer, but I've had the same type issues. The furnace would work like an eight day clock and then like voodoo just decide to not work for a day or so and then just like thst start working fine again. That for me was a circuit board issue and what it seemed to me pointed in your case to a capacitor issue on your circuit board. Otherwise, all you can do is let it ride until or if it doesn't. I carry spares on board for the big 5 most likely to fail parts, ignitor, sensor, limit sw., sail switch and circuit board.
As circuit boards are notoriously unreliable, even out of the box, I like to swap the new board with the old working board as soon as I get the new board. Better to learn if it's a bad board now than later.

Good point. I'll be testing it everyday multiple times to check it for failure. As soon as it starts acting up I'll switch to the other board and see what happens and probe around for voltages on the blower motor.

 

[Bob K4TAX]

When or if you decide to get access, check the blower wheel/motor to see that it turns freely. It might just need a bit of oil lubrication for the motor shaft bearings.

Bob