Shout out to Rick and Gary T: 2001 E 250-noted this morning that the blower doesn’t except in high. That suggests the resistor assembly, but I’m noting in the chassis diagram that there is a thermal fuse inline with all speeds except high. Presuming the thermal fuse to have gone south (which I’ll verify in the AM when I pull the resistor assembly), any idea what temperature value that component has? I’ll happily silver solder or crimp connect a replacement thermal fuse as opposed to buying a new assembly from Ford.
It should be stamped or silkscreened on the side of the fuse. You might need to clean it off to read it. If your eyes are as old as mine, a magnifying glass might help, too.
Yeah-I’m used to that in appliances. Didn’t know if Ford would make it that simple.
Let us know if it does. My secret guess is that all it has is a Ford part number.
I have seen resistor packs that have thermal fuses in them, but they were internal to the pack, and the pack was completely covered in some gray stuff (hard and kind of a pebble grain surface) that prevented you from seeing anything.
FWIW, typically these are mounted in the air flow for cooling. Make sure the air flow to the resistor pack is not obstructed.
Gotcha. The resistor array in my '85 was exposed, and had no thermal element. I’ll have to see if it’s a potted module tomorrow.
ETA: If heat was their concern, why let the high run speed go direct? That would draw the most current. Yes, the resistors dissipate some heat, but ultimately, a fuse would do a proper job of protecting the circuit, no?
The high speed runs via a relay to eliminate any voltage drops, so that the fan runs at full atomic power.
The thermal fuse is not for for current protection, there is a separate fuse in the fuse panel for over current protection. The thermal fuse is thermal protection in case the resistor pack gets too hot. When running in the lower speeds, the resistor pack (in the case of a Volvo) is three resistors in series.
Speed 1 = R1+R2+R3
Speed 2 = R2+R3
Speed 3 = R3
Speed 4= Direct via a relay.
These resistors generate a lot of heat, so the resistor pack in the air flow, and has a thermal fuse. Assuming your vehicle is wired the same way as mine, an open in R3 would be the same as an open thermal fuse.