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.

[DMCMW Dave]

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

Unplug and remove the resistor pack. Nice thing is that you can tell if it is bad with a visual inspection (a bad one will be rusty and have a visibly broken wire inside), and the part is cheap.

[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..

[BladeBronson]

Apologies for not reporting back sooner. The issue was loose wires at the resistor pack. I made sure they were all clean and firmly connected and I haven't had any problems since.

[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:

http://dmctalk.org/attachment.php?attachmentid=59209&d=1549755264

I got a new one:
http://dmctalk.org/attachment.php?attachmentid=59236&d=1549939683

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:
http://dmctalk.org/attachment.php?attachmentid=59238&d=1549940452

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:

http://dmctalk.org/attachment.php?attachmentid=59239&d=1549940731

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! :worship:

[Bitsyncmaster]

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! :worship:

Yes PWM turns power on and off fully so there is no heat generated. A resistor or analog design produce a lot of heat.

[nerdvana]

Yes PWM turns power on and off fully so there is no heat generated. A resistor or analog design produce a lot of heat.

Anyone done this mod yet? Looks like it'd be under $20, considering you can switch 60A for $22: https://www.amazon.com/dp/B07B4B2X35/ref=cm_sw_em_r_mt_dp_U_1mV6CbZ64NR8N
How many amps is the blower?

I ask because my blower stopped working :-) My symptoms are a little weird... none of the speeds spin, but a volt meter at the blower wires shows 8V (with no load) on speeds 1 and 2, and 0V on speeds 3 and 4. My relays look fine, and resistor pack has a little rust but seems to test OK. Circuit breaker has continuity. When I got into the center console I found that the grounding post right next to the fan switch had come lose, but I got that all tightened up and no change. I guess it's my switch?

-Mike

[Bitsyncmaster]

Anyone done this mod yet? Looks like it'd be under $20, considering you can switch 60A for $22: https://www.amazon.com/dp/B07B4B2X35/ref=cm_sw_em_r_mt_dp_U_1mV6CbZ64NR8N
How many amps is the blower?

I ask because my blower stopped working :-) My symptoms are a little weird... none of the speeds spin, but a volt meter at the blower wires shows 8V (with no load) on speeds 1 and 2, and 0V on speeds 3 and 4. My relays look fine, and resistor pack has a little rust but seems to test OK. Circuit breaker has continuity. When I got into the center console I found that the grounding post right next to the fan switch had come lose, but I got that all tightened up and no change. I guess it's my switch?

-Mike

I recall testing my blower on fan speed 4 at 26 amps.

[Ron]

"60 A"! :thumbup:


If you didn't load the thermal breaker during your tests, you might try jumping the Brown (N) wire to the Pink/Black (K/B) wire at #4 relay's socket...

[nerdvana]

If you didn't load the thermal breaker during your tests, you might try jumping the Brown (N) wire to the Pink/Black (K/B) wire at #4 relay's socket...

So I feel like an idiot. It was the fuse “ac mode selector”, not “panel lights”, and it was mostly-blown, leaving enough connection to give me voltage readings, but not enough current to drive anything, including relays. I went on a really uncomfortably hot road trip and I even had the spare fuses with me, if I’d just checked closer.

Anyway, I still want to give PWM a try, but would be neat if there is a way to do it without permanently altering any wiring. Maybe replace the speed-4 relay with a wire so its always on and making use of the circuit breaker, then attach the pwm board to that wire, and try to find a way to get the heatsink of the board up through that little vent opening that the resistors are hiding in? (I assume those resistors are in there to take advantage of forced airflow) Then tuck the original switch back under the radio and put the potentiometer in its place?