Fan Speed 3 Not Working

[BladeBronson]

What would cause only fan speed 3 to stop working? Fan speed 4 works and is on the same fuse. Is it the switch itself?

[David T]

What would cause only fan speed 3 to stop working? Fan speed 4 works and is on the same fuse. Is it the switch itself?

Wire not connected to the fan speed switch
Bad or missing relay or connector backed out in the block
Some other wiring problem. Speeds 3 and 4 each have their own relay.

[DMCMW Dave]

Could be the switch but most likely is the relay esp if it's an original.

Troublshooting chart for fan:

Lost all speeds - likely the fuse or the switch.

Lost speeds 1, or 1 and 2, or 1 and 2 and 3 but not 4 - resistor pack

Lost 3 and 4 but not one and two - circuit breaker.

Or any of the associated wiring in all cases.

Lost speed 3 or 4 only - relay or switch.

[dn010]

Lost speeds 1, or 1 and 2, or 1 and 2 and 3 but not 4 - resistor pack

Where is this located? Losing all but 4 is my exact problem.

[BABIS]

Where is this located? Losing all but 4 is my exact problem.

on the bottom side of the evap. box, near to the blower motor..

[BladeBronson]

Man, leave it to Dave to come through with encyclopedic accuracy. Thanks!

I opened up the panel to check the 3rd speed relay last night, but found that all speeds were working. A few weeks ago, I thought that the 3rd speed wasn't working, but did when I checked the next day, so this seems to be an intermittent problem. My relays are metal with a diagonal red line going through them. I don't know if that indicates the type or age of the relay. Rob Grady inspected my car about a month ago and didn't have any notes about the relays, so I think they're probably up-to-date and correct.

I'll check to see if there's a loose wire on the back of the switch.

[dn010]

Wow, this whole time it was a $6 part! Thank you guys!

on the bottom side of the evap. box, near to the blower motor..

[DMC-81]

Could be the switch but most likely is the relay esp if it's an original.

Troublshooting chart for fan:

Lost all speeds - likely the fuse or the switch.

Lost speeds 1, or 1 and 2, or 1 and 2 and 3 but not 4 - resistor pack

Lost 3 and 4 but not one and two - circuit breaker.

Or any of the associated wiring in all cases.

Lost speed 3 or 4 only - relay or switch.

So, I recently experienced the bolded scenario. I used this thread to troubleshoot (Thanks Dave S!).

Sure enough, my old (original) resistor pack (DMC part number 101275) was the problem. The front resistor (speed #1) is deformed and broken:



I got a new one:


I noticed the new one (nor the parts I cross referenced) came with the original 1/8" foam gasket, so I decided to make one out of some closed foam 1/8" x 10mm wide self adhesive gasket material I had:


This part is located next to the blower fan under the passenger side footwell, and is secured by 2 screws with a 7 mm hex socket head:



Woo Hoo! Now cabin fan speeds 1-3 are working again. Easy Peasey.

[Bitsyncmaster]

Someday I need to look into replacing that resistor with a PWM circuit. My new Toyota has a lot of fan speeds so I guess it has PWM.

[DMC-81]

Someday I need to look into replacing that resistor with a PWM circuit. My new Toyota has a lot of fan speeds so I guess it has PWM.

After needing to ask my friend Google what PWM means, I think this would be great.

For other readers: "PWM = Pulse-Width Modulation. A modern duty cycle control allowing fans and pumps to perform on demand. Unlike voltage control PWM control actually lowers power draw."

You are an electrical wizard Dave!