Blower Repairs

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Contents:

• Blower Resistor Repair
• Blower Motor Repair
  • Order Replacement Brushes On-line

Blower Resistor Replacement:

"My blower only works on high speed..."

Where have I heard that one before? Looking in the Haynes book, I see that there are some resistors connected to the blower motor. High speed runs 12V right to the motor and each slower speed runs through more and more resistance to make the blower motor run slower. I'm a EE, so I like schematics. However, they are just that, a schematic, and not a physical wiring locator. So for the life of me, I could not find the silly resistor assembly. All the other vehicles I have worked on have had the blower located behind/underneath the heater controls in the center of the dash. That's where I was looking and I couldn't find it.

Finally, I convinced myself that the motor by the passenger's right foot was the blower motor. Then, it was really easy to follow the wire bundle from the motor to the firewall, about 3" away (directly towards the front of the truck from the blower motor) approx. 10" above the floor. Right there, screwed into the firewall was the resistor assembly and connector. Yank it out, see the burned out wire coil, get a new one ($16 at the dealer) and plug it in. Done!

Pictured Below:

A: The location of the resistor pack on my '85 4Runner. Taken with blower removed (housing just visible on the right hand edge of the photo. Camera on the fllor, back against the passenger seat shooting forward and to the right.
B: is a good resistor pack, if yours is burned out, it will be obvious, one or more of the wire loops will be burned through. If the wire loops are all intact and you can measure continuity among all the connections (the actual resistance values are all under 1 ohm), then you likely have a problem in the switch or with the motor itself. There also may be a relay and fuse in the center dash area that supply power to the fan.

The new resistor I got has three resistors (and 4 pins on the connector) while my old one had only two. It seems that the newer vehicles have a 4-speed fan. Mine only has 3, although the wiring harness seems to have all 4 wires. Next project may be to find a 4-speed fan switch and see if I can make this upgrade. The lowest fan speed (that I now have) is very low. I think one in between low and medium would be great.

FYI: The way the fan switch and resistor work to control the fan's speed is as follows: The resistor is in series with the fan motor, limiting the current that flows through the circuit and thus the speed of the fan. The resistor has taps along the wire-wound form and the switch supplies power through various sections of the resistor between the taps. Your lowest speed has the full resistance in the circuit. The next speed has the first section bypassed and so on until high speed has the entire resistor bypassed. So one way to trouble shoot the system is to figure out which speeds work and fail and work back from there.

Below is a crude ASCII-schematic of the circuit, when the switch is off, no power goes to the resistor, position 1, power is applied at the first tap, and so on. If for example, speeds 1 and 2 work, but 3 is similar to 1, this might mean that the contact at the 3 position is not good (burned or dirty) or that you have a resistor pack designed for 3 speed operation and the #3 tap doesn't exist.

                   /\/\/\/\/\/\/\/\-+----FAN---->ground
                   o    o    o    o
          off      /1   /2   /3   /4
+12V----o / o------o----o----o----o
                 

Cost:

'85 4Runner Blower Resistor p/n 87138-89103  $16.00 (1998 price)

Here's a p/n for an '86 4Runner: 88635-89103 (4-speed fan)
Here's a p/n for an '89 Pickup:  87138-89105 $34.52 in 2001

Here's a p/n for 1st gen Pickup w/ A/C   :  87138-87004 $ 9.61 in 2006
Here's a p/n for a 1st gen Pickup w/o A/C:  87138-87003 $22.08 in 2006

Rating:
  

Blower Motor Repair:

So after replacing the resistor pack on my 4Runner, I enjoyed seeral years of trouble-free operation. However, after a while I started noticing my blower cutting out on my after longer periods of operation. If I turned it off for a while, it would come back on. I checked the resistors, they were fine, I pulled the switch out, it appeared fine as was the fuse and relay, which I checked by pulling the cover and observing the contacts closing.

So, that left one last source for the problem, the fan motor itself, which is located just above the ECU in the passenger footwell. I removed the kick panel, ECU and disconnected the fan wiring and removed the 3 screws that hold the fan into the housing. I found a small socket on a universal with a short extension worked best for removing the rear most screws. I pulled the fan and motor out, it was filthy, had a few leaves and other junk inside:

So I removed the fan, threw it in the dishwasher, then pulled the 2 screws off the end of the motor and found out the brushes had worn out and the commutator was chewed up pretty good by the arcing brushes. I cleaned up the commutator on my lathe ('cuz I had it, ooh, ooh, OOH :) but a file or some sandpaper or even an ink eraser would work as well:

You can also use a pick or a fine bladed screwdriver to clean out the small gaps between the copper segments in the commutator if they appear filled with carbon and copper dust. These segments need to be electrically insulated from each other, so cleaning the gap out can help restore this condition. Once the commutator was clean, I located a replacement brush, cut off the remnats of the old brushes (they are soldered to the leads) and then soldered the brush leads to the brush holders (lower left image). The replacement brushes have springs and shunts soldered to them already, so just slip them into the brush holder (middle image) and slip the commutator into the brush assembly (lower right). Be sure to put a few drops of oil in the bronze bushing before inserting the motor shaft.

In the above center image, on the left are my old worn out brushes and on the right are the new replacements.

Now slip the other end of the motor into the housing, oil the bushing at the other end, install the screws and fan (below):

And bolt the fan back into the housing. It should fire right up, be sure to check operation on all the speeds. The motor will be a bit noisy until the brushes and commutator break in. Since my original brushes lasted 15 years and 240,000 miles, I think the new ones will be a good investment.

Replacement Brushes available on-line:

Toyota considers the blower motor a sealed, non-repairable unit so don't offer a replacement brush kit. 4Crawler Offroad has designed and manufactured replacement brush assemblies ready to install in your Toyota fan motor (size is 0.25" x 0.23" x 0.50" long) for sale. Fits most common Toyota blower motors (pickup, 4Runner, Celica, and others. Also available for Honda vehicles (Prelude, etc.) as well (0.25" x 0.25" x 0.50" long).

Cost is $22.00 for the pair plus shipping, or several other expedited shipping options at additional cost. Contact 4Crawler Offroad for more information.

So, why not just go to the local junkyard and grab a spare fan motor? I suppose that would work as well. Often, the ratio of pick-n-pulls to people is pretty low and the prices are correspondingly high and selection poor. So, often it is better to repair instead of replace. Also, if you grab a 15 year old fan out of a junker, it may be in no better shape than the one you already have.

Note, if considering the brush replacement:

• You should first determine that the brushes are indeed worn out by removing the fan motor and inspecting it.
• This will also ensure that you can remove the fan motor and actually open up the motor.
• Some units may be more difficult to work on and if you have a fan motor that is sealed up tight and resists opening, replacement may be the only option.
• Brushes also fit some Honda blower motors as well as Hitachi 4-1/2" (and possibly other model) angle grinders:
  • Contact 4Crawler Offroad to discuss your carbon brush needs