blower motor resistor

[Ray_Bronco]

i was wondering if someone my know the answer to this. I replaced my fan blower resistor since it was only working on high speed. the new resistor worked for about a day then it went back to only working on high speed. i got another resistor worked perfectly for about a day then quit working... a few hours later it was working again. the next day it was only working on high speed. i used Standard resistors for both of the installs so I doubt it is the resistor...
any ideas what could be causing the resistor to fail after only one/two days.
thanks
ray

 

[Tiha]

Blower motor is probably drawing too many amps and burning up the resistor.

Should look at the blower motor next.

 

[Ray_Bronco]

Blower motor is probably drawing too many amps and burning up the resistor.

Should look at the blower motor next.

i replaced the blower motor with a brand new one when i replaced the first resistor.. I can try to test.

 

[Tiha]

i replaced the blower motor with a brand new one when i replaced the first resistor.. I can try to test.

It is possible then that you have a wiring or switch issue. Just really weird that replacing the resistor seems to make it work for a couple days.

What about turning it on, then wiggle wires around the resistor or blower motor?
Don't be gentle.
Heck, maybe even spray water on them?

Those weird ones like this always ****.

 

[Ray_Bronco]

It is possible then that you have a wiring or switch issue. Just really weird that replacing the resistor seems to make it work for a couple days.

What about turning it on, then wiggle wires around the resistor or blower motor?
Don't be gentle.
Heck, maybe even spray water on them?

Those weird ones like this always ****.

i will try... im not that savy on electrical issues. i was thinking of the fan switch. its funny because when the 2nd replacement installed. it worked for a day, stopped working then later in the day it started working again (all three speeds) .. 3 days later only on high.. if i cant figure it out it has to go in to get my a/c and cruise control looked at so i will wait til it gets warmer out. at least i have it on high so that is something.. thank you

 

[Tiha]

It certainly could be the blower switch. Could find a loose or burnt terminal on the back of it.

When there is a lose connection it creates more resistance, More resistance creates more heat. More heat melts switch, or breaks connection until it cools down at least to start the cycle all over again.

 

[Ray_Bronco]

It certainly could be the blower switch. Could find a loose or burnt terminal on the back of it.

When there is a lose connection it creates more resistance, More resistance creates more heat. More heat melts switch, or breaks connection until it cools down at least to start the cycle all over again.

thank you again for your help on this.. im good at looking for melted wires and relays... not too good at electrical troubleshooting.. have a nice weekend.

 

[goodO1boydws]

Someone already touched on this, but to be more specific, if you have a weak connection in the plug from the wiring harness to the resistor (from the dreaded green or white corrosion-with or without loose powder being present) it could be making and breaking contact as the wiring moves around-or from changes in ambient temperature. (Also check and burnish the connector for your interior fan switch. See below)

Take a close look and if you don't see anything obvious, at least connect and disconnect that plug several times to burnish the contacts. If it then works more reliably, shoot some electrical contact cleaner (or solvent type carb cleaner) into it, burnish it some more, and spray more cleaner into it afterwards. Then let it dry out completely and put dielectric grease in it. That keeps the connection protected against moisture and a repeat situation. When I do this cleaning-out I put a rag or paper towel under the connector to see what, if anything, comes out. It also helps contain the dripping solvent.

If you do find ANY connector that has this sort of corrosion, its a good idea to check every other one that you can for the same thing. More exposed wiring for external devices (turn signals, headlights, brake lights, etc) are especially vulnerable to this.

This type of corrosion inside connectors is something that's common in older vehicles-especially if they've spent time in the rust belt or any area where road salt is used, (or near the Salt Flats), or close to an ocean with the salt air exposure.

DON'T DO THIS WHILE SMOKING OR NEAR A HOT ENGINE OR A NEARBY HEAT SOURCE IF USING ANY VOLATILE SOLVENT CLEANER.

 

[Ray_Bronco]

Someone already touched on this, but to be more specific, if you have a weak connection in the plug from the wiring harness to the resistor (from the dreaded green or white corrosion-with or without loose powder being present) it could be making and breaking contact as the wiring moves around-or from changes in ambient temperature. (Also check and burnish the connector for your interior fan switch. See below)

Take a close look and if you don't see anything obvious, at least connect and disconnect that plug several times to burnish the contacts. If it then works more reliably, shoot some electrical contact cleaner (or solvent type carb cleaner) into it, burnish it some more, and spray more cleaner into it afterwards. Then let it dry out completely and put dielectric grease in it. That keeps the connection protected against moisture and a repeat situation. When I do this cleaning-out I put a rag or paper towel under the connector to see what, if anything, comes out. It also helps contain the dripping solvent.

If you do find ANY connector that has this sort of corrosion, its a good idea to check every other one that you can for the same thing. More exposed wiring for external devices (turn signals, headlights, brake lights, etc) are especially vulnerable to this.

This type of corrosion inside connectors is something that's common in older vehicles-especially if they've spent time in the rust belt or any area where road salt is used, (or near the Salt Flats), or close to an ocean with the salt air exposure.

DON'T DO THIS WHILE SMOKING OR NEAR A HOT ENGINE OR A NEARBY HEAT SOURCE IF USING ANY VOLATILE SOLVENT CLEANER.

i will try that.. i used di-electric grease w/ the new connection.. not to worry when i use contact cleaner (w/h i have) i will also turn off the bbq grill.. just kidding.. good to remind people that this stuff is flammable... i figured its a loose connection that is shorting out.. the fun is finding it.. its like where is waldo but w/ electric wiring

 

[miesk5]

Yo Ray,
FYI,
Also, see;
Leaf & Debris Build-Up Location pic in 80-96 Blower Motors & Ducts
Source: by banned member Steve83

Following in 96 Bronco/F Series Workshop Manual http://www.diesel-dave.com/vehic/manual/stj/stjc0022.htm#extract_1259
"Blower Motor
To test the blower motor (18527), connect a No. 10 (or larger diameter) jumper wire directly from the positive battery terminal to the positive lead of the blower motor. If the blower motor runs, the concern must be external to the blower motor. If the blower motor will not run, connect a No. 10 (or larger diameter) jumper wire from the ground lead of the blower motor to a good ground. If the blower motor runs, the fault is in the ground circuit. If after testing the positive and negative sides of the blower motor, the blower motor still will not run, the blower motor must be replaced.

Blower Motor Resistor
To test the blower heater blower motor switch resistor (18591) as well as the internal thermal limiter, check continuity for shorts or opens with a self-powered test lamp. If the unit indicates an open or short, it cannot be repaired and will require replacement."

 

[goodO1boydws]

Yo Ray,
FYI,
Also, see;
Leaf & Debris Build-Up Location pic in 80-96 Blower Motors & Ducts
Source: by banned member Steve83

Following in 96 Bronco/F Series Workshop Manual http://www.diesel-dave.com/vehic/manual/stj/stjc0022.htm#extract_1259
"Blower Motor
To test the blower motor (18527), connect a No. 10 (or larger diameter) jumper wire directly from the positive battery terminal to the positive lead of the blower motor. If the blower motor runs, the concern must be external to the blower motor. If the blower motor will not run, connect a No. 10 (or larger diameter) jumper wire from the ground lead of the blower motor to a good ground. If the blower motor runs, the fault is in the ground circuit. If after testing the positive and negative sides of the blower motor, the blower motor still will not run, the blower motor must be replaced.

Blower Motor Resistor
To test the blower heater blower motor switch resistor (18591) as well as the internal thermal limiter, check continuity for shorts or opens with a self-powered test lamp. If the unit indicates an open or short, it cannot be repaired and will require replacement."

The leaf buildup there can be a BIG problem.
My B2 is parked outside nearly all the time and we live in a heavily forested area of mixed softwood/hardwoods.
I'm pretty good about blowing out leaves from the engine engine compartment and off the vehicles after the leaves stop falling.
I thought so anyway.

I was driving along one day when I thought I smelled smoke(which isn't unusual around here as many people burn wood for heat).
Then dense smoke started pouring out of the engine compartment.
If you've ever seen a CO2 fire extinguisher in use that's how dense the smoke was-INSIDE the vehicle.

Luckily, there were no vehicles nearby and I could quickly pull over. After I pulled over the airflow slowed, and the smoke abated enough that I could tell where it was coming from. It was still smoldering-(after turning the fan off) but slowly enough that after pouring the bottle of soda I had on hand down the cowl intake venting, I let it burn until it died out by itself. I hosed the intake area down when I got home to be sure it was out.

The HOT coil of wire (the resistor), for the speed of the blower that it was set on, aided by the air still able to flow through an accumulation of leaves had started them smoldering inside the plenum.

I don't know what was originally used as screening to block leaves from come through or if it was never there-a slipup during assembly, or after an accident was repaired. (If it didn't have screening from the factory it would be a fire hazard from day 1.)

I added some metal screening after digging out a large amount of decomposing and fresher leaves that had been accumulating there to nearly encase the resistor for who knows how many years. That was after exploring areas I couldn't otherwise reach by using a stiff wire, and blowing the plenum out repeatedly with compressed air. I used the smallest mesh galvanized l hardware cloth-I think it was 1/8" x 1/8".

 

[Ray_Bronco]

Blower motor is probably drawing too many amps and burning up the resistor.

Should look at the blower motor next.

i replaced the blower motor when i did the resistor