ubject: MK5 Transit blower fan burned out after switch upgra

[vtkr]

About six months ago, I bought an ex-water utility MK5 Transit with the raised roof. At the time of purchase, the interior blower fan control had been modified: the original fan switch had been replaced with a resistor and a single-speed toggle switch.

Recently, I sourced a used but functional 3-speed fan switch from a breaker yard and installed it to restore the original functionality. After the swap, the fan worked correctly across all three speed settings.

However, during the first proper rainy drive where I had the fan running on the 3rd (highest) speed for an extended time—not just for a quick test—the cabin filled with the smell of burning electronics and the fan stopped working entirely.

I’m guessing the fan speed controller has burned out, but I haven’t opened it up yet to confirm. My understanding is that on speed 3, the fan motor receives full power directly without going through any series resistor. This makes me wonder if the fan motor itself may be faulty or drawing too much current, and if that might be what caused the controller to fail.

Has anyone run into something similar with the MK5 Transit? Would it be wise to replace the blower motor as well, or are there specific components (e.g., wiring, relays) I should inspect first to trace the root cause before throwing parts at it?

Any advice or shared experience would be greatly appreciated!

[MinorMatt]

Check the fuse (they melt)
Motors can seize
Switches can burn out

[V184]

Check the fuse (they melt)
Motors can seize
Switches can burn out

As can the wiring plug

[MinorMatt]

Check the fuse (they melt)
Motors can seize
Switches can burn out

As can the wiring plug

The plug and wiring normally go together

[V184]

Check the fuse (they melt)
Motors can seize
Switches can burn out

As can the wiring plug

The plug and wiring normally go together

Remember seeing them burn out at other end where the sub loom plugs in

[MinorMatt]

Thats true - Ive had that too, but less common

[bortaf]

Ive had this quite a few times, the heater motor is/was/has seized and the load required to turn it had melted the switch, the usuall "quick fix" is to fit a higher amp rated switch and run it on full or off, but doing this meens usually the wiring and pug and fuse soon follow and melt, if you keep avoiding the fix eventually the main ign switch plug under the steering column also melts and the van stops running untill it cools down again, fitting a new fan motor usually fixes it IF the wiring/plugs ect are OK.

I had one mk5 come in with 2 wood screws jammed into the wiring, you touched them together and the fan ran, eventually the 2 screws welded together and then the owner bought it in to be fixed

[V184]

Ive had this quite a few times, the heater motor is/was/has seized and the load required to turn it had melted the switch, the usuall "quick fix" is to fit a higher amp rated switch and run it on full or off, but doing this meens usually the wiring and pug and fuse soon follow and melt, if you keep avoiding the fix eventually the main ign switch plug under the steering column also melts and the van stops running untill it cools down again, fitting a new fan motor usually fixes it IF the wiring/plugs ect are OK.

I had one mk5 come in with 2 wood screws jammed into the wiring, you touched them together and the fan ran, eventually the 2 screws welded together and then the owner bought it in to be fixed

Seems a dangerous game to play