"Real Wheelers Are Built, Not Bought"
The Toyota heater - A/C - blower system is fairly simple. There is a
fuse, a switch, a relay, a resisto pack and the blower motor attached
to the fan. All parts are inside the cab, on the passenger side of the
dash. The switch of course is in the center of the dash. In the off
position, everything is off. In the various numbered positions, it does
two things, one is to turn on the relay that sends power to the fan and
then it switches in various segments of the resistor pack to control
the motor speed and air flow. The fuse and relay are under the dash, on
the passenger side, mounted on the side of the center portion, sort of
behind and to the left side of the glove box. You'll likely need to
remove the glove box to gain access to the fuse and relay.
For testing, if you touch the relay, you should be able to feel it
click on and off as you move the fan swtich on and off. If it does,
that likely means the relay is fine. Pull the fuse to inspect it. For
other issues, the most common failure is the resistor pack, common
issue is loss of all the lower speeds. Worn out motor brushes are also
somewhat common, you may find the fan does not run or runs slower than
normal or runs for a while then shuts off (due to overheating). The
third most common problem is burned contacts on the fan switch itself.
For this, you need to disassemble the dahs enough to gain access to the
fan switch. The burning is usually visually evident, replacement is the
likely fix. ANd this would be the order in which you should probably
approach blower problems. Checking the fuse and relay is easy. Resistor
pack is also pretty easy to check, the fan motor is kind of tricky to
access as one of the 3 screws holding it in place is hard to reach. And
finally, the fan switch replacement is the most involved task, so try
the easy things first.
"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!
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
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.
o o o o
off /1 /2 /3 /4
+12V----o / o------o----o----o----o
+12V----o / o------o----o----o----o
One thing to watch for is if you want to test the fan out before
installing the resistor back into the air duct and that is the resistor
will get hot, as in VERY HOT in use. Without the air flow inside the
duct to cool it, it will get hot enough to burn your skin, so beware!
'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
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,
With your new brushes in hand, you'll see that they have a spring
attached, like the OEM brushes, but that also have a braided copper
pigtail connected between the end of top of the brush and the end of
the spring. The OEM brushes have the same spring, but the copper
pigtail connects between the brush and the connector on the brush
holder assembly. So, as a one-time modification, you just want to cut
off the remnats of the old brushes from teh copper pigtail (cut as
close to the brush as you can manage to preserve as much lead length as
possible) and then solder the ends of the old brush leads to the brass
metal brush holders (lower left image - solder joints circled in red).
For this step, you'll want to clean the area on the brass well with
some steel wool or fine sand paper to leave shiny clean metal. Then
with a hot soldering iron, "tin" the clean brass by holding
the iron to the metal a few seconds to heat it up enough so that the
solder melts when touched to the hot brass. Then tin the end of the
copper braid from the old brush and finally touch that braid end to the
tinned area on the brush holder and apply the soldering iron on top and
hold until the solder melts and bonds the pigtail to the brush holder.
Once it cools, give the pigtail a tug to make sure it is a good solid
connection. 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). This
modification needs to be done only this one time, as if in the future,
these replacement brushes wear out (maybe another 200K miles or so),
you can pull them out and simply pop in a new pair and be back on the
road in no time.
Also, be sure to put a few drops of good lubricating oil in the bronze
bushing before inserting the motor shaft. You want an oil that is not
too thin (like WD40, Liquid Wrench, etc., these oils are too thin and
will dry up in a few days) but not as thick as engine or gear oil, so
just use a good light machine lubricating oil.
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. You may also notice the blower motor will run a
little slower than it did with the old brushes. This is because carbon
brushes have a certain ressitance per unit length. A longer brush will
have a higher resistance (and thus flow less current) than a shorter
brush (note the length difference in the above-center photo). In fact
on my blower, this is why the motor would overheat and shut down with
continued use, it was essentially pulling too much current and
overheating. We try to size the brush to be as long as can fit into the
brush holder to ensure maximum service life. But the tradeoff is that
the motor will run slower than it did with the old worn out brushes. It
is the same idea as the way race cars will run tires where they shave
down the rubber very thin. They can run faster without overheating, but
have to change tires a couple of times ina 500 mile race, compared to
your typical road tires where you can expect 40,000 miles or more of
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" (6.35mm) x
0.23" (5.84mm) x 0.50" (12.7mm) long for sale. Fits most
common Toyota blower motors (pickup, 4Runner, Celica, and others
(select Toyota application). Also available for Honda
vehicles (Prelude, etc. - select Honda application)) as
well (0.25" x 0.25" x 0.50" or 0.75" long). and you
can trim the brushes to fit. Note these brushes also fit the Hitach
4.5" angle grinder (select Generic application).
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?
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 and you have to remove both the blower in your
truck and the blower in the junkyard truck, so it is twice the work and
Note, if considering the brush replacement:
[Last updated: 15.February.2013]