12 Volt Heater Blowing Fuse?

[HandyAndy1947]

About four years ago, I completed the restoration of my Harrison fresh air heater to include the 12 volt motor, potentiometer, and DC motor controller. Twice now (in four years) it has blown the 10 amp fuse. Has anyone else had a problem like this? It doesn't have much run time on it and after the fuse is replaced it is fine, until it isn't. I'm reluctant to put a bigger fuse in the system, so I thought I'd run this by you. I see in your schematic the 12 volt DC motor controller is rated up to 20 amps. I'm just wondering if I have a component problem or an under fused circuit.

Let me know your thoughts, thanks!

[Deve]

Hi Andy! Well, haven't run into this before, but if the motor is running smoothly without issue and the wires are not coming undone behind the switch causing an intermittent short, and the wiring is the standard 18 gauge, you can put a 15 amp fuse in it without problems. If it blows that one, and the wiring is solid, I would replace the controller first since its cheap and easier than replacing the motor first.

[HandyAndy1947]

Hello Deve!

I've confirmed all wiring is sound and intact. I put a 10 amp fuse in (since I had some) and the motor sounds smooth and steady throughout the operating range, from low to high. I'll run it this way for a while and see how it operates......

Thanks for your input!