Blower High Only - Resistor Visually Good

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Lurkur
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Blower High Only - Resistor Visually Good

Post by Lurkur »

Hello I'm writing another HVAC system article. This time its for blowers that only work on high, but the resistor is visually OK.

The repair should take less than an hour. You will need a PH2 screwdriver, a pick, needle-nose pliers, a multimeter, a hammer, a punch, and an optional drill.

Start by opening the hood. Remove the hood gasket on top of the firewall. Undo the three screws that hold the driver side solid wiper cover to the vented wiper cover.

On top of the evaporator box in the center of the car is the resistor. Undo the two screws, the blower motor output tab, and the speed switch connector.

Before going further with the repair, test the resistor to make sure this tutorial can repair it. The two resistive coils must not be broken and should measure a couple ohms between tabs. You must measure a short circuit across the thermal fuse for continuity. This is the small cylinder between the two coils of wire. A picture is below;
https://i.imgur.com/NcxUo0e.jpg
If this is an open circuit, the fuse has failed and needs replacing. This seems to be a common problem. Its originally a Microtemp fuse rated at 121c and ~15A. There are many suitable replacements still available at your local electronics store or online. I chose NTE8139 because it was local and exceeds the original temp rating by 20c.

The replacement fuse cannot be soldered in because the temperature would damage the fuse. You need to open up the crimps with a pick so the replacement may be installed. Take your time. You can easily stab your finger or damage the part.
https://i.imgur.com/HVmN5gn.jpg

Optionally, I used a small drill to enlarge the crimps to fit the larger lead diameter of this fuse.
https://i.imgur.com/rpWlIwf.jpg

I bend the fuse leads to prevent it from touching resistive coils and install with epoxy end facing the blower motor output tab. Use a hammer and a punch to crimp the new fuse in place.
https://i.imgur.com/Vij8fGG.jpg

The resistor is now ready to reinstall in your car.
Ed Lijewski
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Re: Blower High Only - Resistor Visually Good

Post by Ed Lijewski »

That unit is called the BCM- Blower (Motor) Control Module.

The typical cause of the fuse failure is excessive current draw likely due to crud/corrosion on the blower shaft ends at their bushings. The shafts can be cleaned/polished manually...if/when the fan motor is removed from the blower/evaporator case.

YMMV
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my8950
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Re: Blower High Only - Resistor Visually Good

Post by my8950 »

Check it with a meter, you'll most likely find the resistor/fuse is open.
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andyofcolumbusmerkur
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Re: Blower High Only - Resistor Visually Good

Post by andyofcolumbusmerkur »

Thanks for the good info. I will have to order a NTE8139. I like how that has a higher rating than stock. :headbang
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Re: Blower High Only - Resistor Visually Good

Post by Ed Lijewski »

andyofcolumbusmerkur wrote: Mon Jan 08, 2024 1:12 pm Thanks for the good info. I will have to order a NTE8139. I like how that has a higher rating than stock. :headbang
Even higher rated thermal fuses are available. It's been several years since I did the fix but IIRC I used a higher C* rating. My memory is I also got a thermal fuse or two off the shelf from MicroCenter (they don't stock a variety but what they did stock was okay for this use).
20180226_160543-1.jpg
20180226_160543-1.jpg (1.78 MiB) Viewed 23331 times
YMMV
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Re: Blower High Only - Resistor Visually Good

Post by my8950 »

I have some from Radio Shack... :)
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