FJ40 Rear Heater Fan - only one speed (1 Viewer)

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Wake Forest, NC
Hi All -

My rear heater fan only operates at high speed (1970) and not the low speed. FYI - it is an earlier dual speed fan. Any one have this issue? Does this tend to be a switch issue, or an issue with the resistor on the actual fan?

Thanks for any help
 
well .....


it can be one
 
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I'm more familiar with the later 40's rear heater which only works when the fan is on high. I believe you have a separate switch, right? I would either replace the switch or the resistor on top of the blower motor.
 
All the harnesses leading to the heater have two wires at up to 74. Need to see how many wires the motor has to tell if it's single speed or two. If the motor has two wires on it's side of the plug it should be a two speed motor.
 
All the harnesses leading to the heater have two wires at up to 74. Need to see how many wires the motor has to tell if it's single speed or two. If the motor has two wires on it's side of the plug it should be a two speed motor.
Yes, it is a two wire.

So I checked voltage to the fan. I got 12 volts on both high and low settings. So, I figured it was the resistor on the fan. Changed out the resistor (I happened to have a spare). Got the same result. Pulled the switch (breaking the knob while doing so) and cleaned it. Reinstalled and got the same result. Could it be a grounding issue?
 
Hi All -

My rear heater fan only operates at high speed (1970) and not the low speed. FYI - it is an earlier dual speed fan. Any one have this issue? Does this tend to be a switch issue, or an issue with the resistor on the actual fan?

Thanks for any help

YES it can be just that !

see below ,,,
 
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Yes, it is a two wire.

So I checked voltage to the fan. I got 12 volts on both high and low settings. So, I figured it was the resistor on the fan. Changed out the resistor (I happened to have a spare). Got the same result. Pulled the switch (breaking the knob while doing so) and cleaned it. Reinstalled and got the same result. Could it be a grounding issue?


If high speed working seriously doubt you have a ground issue. Have you verified fan is not running with the cover off? I know the ones I have with two speeds can hardly notice air movement on low. I would try jumping across the resistor when in low speed. Should run on high jumped. These only have a single winding. Low is just the winding in series with the resistor.
 
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If high speed working seriously doubt you have a ground issue. Have you verified fan is not running with the cover off? I know the ones I have with two speeds can hardly notice air movement on low. I would try jumping across the resistor when in low speed. Should run on high jumped. These only have a single winding. Low is just the winding in series with the resistor.
Yes, took the top off to check fan. Got it to run at low speed one time, then it stopped. I’ll try the jump you suggested.
 
Possible have a poor connection in the switch where is should voltage on a meter but not strong enough connection run the motor. Since your already working with the resistor might switch the high and low speed connections on the resistor. High speed is a known working circuit. Connected to series thru the resistor is another test to perform.
 
If high speed working seriously doubt you have a ground issue. Have you verified fan is not running with the cover off? I know the ones I have with two speeds can hardly notice air movement on low. I would try jumping across the resistor when in low speed. Should run on high jumped. These only have a single winding. Low is just the winding in series with the resistor.
Yes, it is a two wire.

So I checked voltage to the fan. I got 12 volts on both high and low settings. So, I figured it was the resistor on the fan. Changed out the resistor (I happened to have a spare). Got the same result. Pulled the switch (breaking the knob while doing so) and cleaned it. Reinstalled and got the same result. Could it be a grounding issue?


- OEM-TYPE Genuine SKUNK-WORKS Part # 82213-60010 ADD -ON -GROUND sub harness for a 2 speed rear heater , u piggy-back along the existing 2 blue w. tracer stripes wires ..,.

- the Polarizes the Entire REAR Heater blower MOTOR it-self directly via one of the three TINY 4mm phillips head machine screws on FEET of blower motor directly ...

-


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01693900-17D2-42CF-8A3F-C1B67061C1EC.jpeg
26968EAA-4DF5-45B2-93A5-A2C1C6568F38.jpeg
C579E3FF-AD64-415E-9FF3-53ABA261D143.jpeg
 
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I have not taken my rear heater apart but the schematics show front AND rear have 2 speeds. My initial thought would be the switch lowers the voltage to the motor because the rear is a 2 wire setup.



Rear heater.png
 
I have not taken my rear heater apart but the schematics show front AND rear have 2 speeds. My initial thought would be the switch lowers the voltage to the motor because the rear is a 2 wire setup.



View attachment 3311504


Rear heater is like the front heater. If it's a two speed it will have a resistor by the heater motor not in the switch. High speed wire is soldered to the same side and the motor winding wire. Low speed is soldered on the other side of the resistor so in low speed it's in series with the resistor. High speed bypassed the resistor.
 
Rear heater is like the front heater. If it's a two speed it will have a resistor by the heater motor not in the switch. High speed wire is soldered to the same side and the motor winding wire. Low speed is soldered on the other side of the resistor so in low speed it's in series with the resistor. High speed bypassed the resistor.
This is correct. Switch has no resistor. I took it apart and checked.
 
Rear heater is like the front heater. If it's a two speed it will have a resistor by the heater motor not in the switch. High speed wire is soldered to the same side and the motor winding wire. Low speed is soldered on the other side of the resistor so in low speed it's in series with the resistor. High speed bypassed the resistor.

I see. The switch takes the 12 volt to another part inside the design. So, high speed is no resistor and when switched 12 volts goes to resistor and then becomes low speed. Seems ok and I appreciate this knowledge as I plan to restore my rear heater soon.
 
Have you checked the resistor ? If it is marked with a value , perhaps it failed in open circuit. Then no power will reach it. Another way to tell is remove the resistor , then connect a wire where the resistor was, and the motor should run high for both positions.
 
Bad ground could be the problem.

Bad ground effectively causes resistance. So, high speed with ground resistance is really a lower speed, and low speed switch adds even more resistance through the resistor, to the point there's not enough voltage to run the motor.
 
Bad ground could be the problem.

Bad ground effectively causes resistance. So, high speed with ground resistance is really a lower speed, and low speed switch adds even more resistance through the resistor, to the point there's not enough voltage to run the motor.


A couple of wires with alligator clip on the ends would make trouble shooting a lot easier. While running on high speed jumper the motor caee to a known good ground and watch the motor speed. Same with jumper around the resistor in low speed. Like most electrical issues on the old cruisers trying to solve over the internet is a lot harder than actually working with the part in person.
 

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