Blower motor resistor fails from heat

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Jinxyjuice

Joined Aug 21, 2021
2
My a/c blower fan resistor in my truck fails and causes the fan to work only on high. Apparently it’s just a poor design with the resistor being to close to the heat sink coils. The dealer recommends spreading the coils apart to allow for better heat dissipation. This doesn’t always seem to work as other vehicle owners stated.
I was thinking about cutting a 1’’ piece of heat resistant wire loom material and placing it between the resistor and coil to shield it from heat.
Any thoughts or ideas would be appreciated.
 

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LowQCab

Joined Nov 6, 2012
1,189
That's not a Resistor, that's a Diode.
Normally Blower-Resistors fail because of cheezy "Push-On" Connectors
trying to handle ~30-Amps,
with Wires that are too small,
and in a damp, 200F environment, (think virtually Steam).

If You get ~3-years of service out of it you're doing great.

If it's actually the Diode over-heating,
bend it away from the Resistance-Elements.

There should be a continuous flow of Air over this unit,
look at which way the a flow is going,
maybe You can install it flipped-around for more advantageous Air-flow.

They've been doing it this way for almost a century, it's "Par for the Course".
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It's not a diode. It's a thermal fuse. There should be a temperature rating on it. What are all of the numbers on it?

I've had blower resistors go bad, but for different reasons.
a) brushes
b) Fan hitting against the housing

a) Fixed with vacuum cleaner brushes and brass shims and a file.

b) Blower was held by friction. When it got really hot outside, gravity would do it's thing and the blower would hit. Solution: push it up every once in a while during the summer. Pay attention when it's hot outside

The thermal fuse may not be rated for the current.
 

bwilliams60

Joined Nov 18, 2012
1,419
The unit as mentioned is a thermal fuse. I am guessing this is in a Ford truck or van. These resistor blocks were designed to be placed in the path of airflow to keep them cool. These units have a lifespan on them, generally about ten years and then for about fifteen bucks or so, you replace them. If you wanted to cheap out, you could replace the thermal fuse. The worst part about these, is generally the connector. They should be replaced at the same time because if you drag test them, you will often find they will fail. Replace resistor and connector and enjoy the next ten years. Former Ford tech.
 
Replace resistor and connector and enjoy the next ten years. Former Ford tech.
I did have a problem with a connector too on a Chevrolet. Forgot about that. The Impala had a bad design too. Sometimes, aftermarket parts fixes issues with original designs.

This https://www.cool-amp.com/conducto-lube product is fantastic especially after you get things the way they are supposed to be. if I can find my container, I might be able to send you some for a few contacts.

Connector damage is a possibility.
 

GetDeviceInfo

Joined Jun 7, 2009
1,897
The unit as mentioned is a thermal fuse. I am guessing this is in a Ford truck or van. These resistor blocks were designed to be placed in the path of airflow to keep them cool. These units have a lifespan on them, generally about ten years and then for about fifteen bucks or so, you replace them. If you wanted to cheap out, you could replace the thermal fuse. The worst part about these, is generally the connector. They should be replaced at the same time because if you drag test them, you will often find they will fail. Replace resistor and connector and enjoy the next ten years. Former Ford tech.
My Rockauto replacement unit didn’t last a year, and the wrecker inventory is scavenged. Off to Ford I go.
 

Tonyr1084

Joined Sep 24, 2015
6,374
That's not a Resistor, that's a Diode.
No. See KISS's comment
It's not a diode. It's a thermal fuse.
Yes. Had one go out on mother-in-law's washing machine. Replaced it for less than $2.00. Used slightly higher rated "Fusible Link".
These resistor blocks were designed to be placed in the path of airflow to keep them cool.
Yes. If not they would overheat. Sometimes dust can accumulate on them and inhibit their ability to be cooled by the airstream. Mom's Oldsmobile experienced the same failure. Replaced it with OEM (Original Equipment Manufacture) and problem was gone for the rest of the life of the car.

Auto manufacturers look for ways to keep costs down. They could have gone with an electronic package, but this solution was so elegantly easy. And cheap. Me? I'd go for a new OEM replacement and be done with it.
I was thinking about cutting a 1’’ piece of heat resistant wire loom material and placing it between the resistor and coil to shield it from heat.
Any thoughts or ideas would be appreciated.
That would defeat its purpose. The purpose of a fusible link is to blow out in the presence of an over-temp condition, thus preventing a fire from occurring. If you don't mind driving a carbecue then proceed to defeat the FL. Oh, and don't try to solder in a new one - I learned the hard way that this will blow the FL too. Notice in your pics they're welded in probably via ultrasonic welding. Not certain about that, but they're definitely not soldered in.
 

bwilliams60

Joined Nov 18, 2012
1,419
If you have ever read any of my posts in the past, a lifetime of experience in automotive electrical has always led me back to OEM products for electrical and driveabilty parts(sensors, modules etc). They are made to specs, not reverse engineered, and will almost always outperform aftermarket parts. There are a few companies that make good products in electrical but unless you are in the business, it is hard to know what products and what companies to use. I have also found OEM to be cheaper in a lot of cases. You get what you pay for.
 
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