So, my fan motor died a long time ago and I replaced it, but in doing so I believe I fried the original fan speed switch in the dash. So, I rewired the fan motor using an on/off switch. I'm wondering if there is a variable switch that I could use. Do I need a certain type or will any work?

the speed control is done by a series of three resistor coils under the passenger side dash near the fan motor, their is a thread here someware that has pictures, anyhow their easly replaced, less than 5 minits, you can get a known good one from a junk yard , or you can make new coils with nichrome wire and solder them in, either way its very easy

Well, as I explained, I already rewired the motor and don't intend to fix the stock switch anytime soon. So, is there a switch that I can buy for what I want it to do?

So, is there a switch that I can buy for what I want it to do?

 

It is a combination of a switch AND power resistors that makes the speed changes. The power resistors have to disipate a lot of power, so they are mounted in the blower housing for cooling. If your resistors are good, you need a single pole 4 position switch that can handle 20 Amps.

 

For more information than anyone should want to know about EA82 blower motors & speed controllers, including voltages, current, power ratings:

http://www.ultimatesubaru.org/forum/showthread.php?t=64761&highlight=speed

 

About the 3rd page in starts the more detailed stuff.

I've never seen the actual switch fail. I'll bet it's the resistor block. Does the fan work on HI speed? You probably damaged the delicate resistor coils while installing the new fan. You had to have removed the reistor block to take out the fan. What shape were the coils in?

This was over 1 year ago when I replaced the blower fan motor. IIRC, the resistors were damaged by an accidental electrical contact that I made when installing the new blower motor (I don't believe any of the speed settings were functional after that). To make the fan functional, I spliced a switched wire in from the key-ignition harness to draw power in the ignition-position 'ON' such that the fan operates @ 100% power ONLY.

 

What I was thinking is that there might be switches w/ variable states of resistance to function similarly to the original 4 speeds.

 

What I was thinking is that there might be switches w/ variable states of resistance to function similarly to the original 4 speeds.

 

No, there are not any that I know of. That is why subaru and nearly every other manufacturer uses a resistor block in the ground circuit.

 

Since you have eliminated the engineered solution to this problem Subaru designed, you aren't really asking a subaru question anymore. You may have better luck asking on an electrical forum

No, there are not any that I know of. That is why subaru and nearly every other manufacturer uses a resistor block in the ground circuit.

 

There are alternatives, but they are more expensive, impractical, or require fairly high level electronic design work. Most are 2 of the 3. The details are all buried in the previously mentioned thread.

Okay that answers my question, thanks. I was just hoping for a cheap switch or some such; I can live w/ an on/off switch for now.

I'm thinking that a dimmer light switch should work. Hopefully I don't destroy the motor or blow a fuse.

I'm thinking that a dimmer light switch should work. Hopefully I don't destroy the motor or blow a fuse.

 

It won't. The reason lies with the amerage draw of the motor. The draw is high enough to burn out all but some of the largest rheostat's (the "dimmer" switch you mention). A "dimmer" style switch large enough to disipate that kind of heat would be 3"+ in diameter, and might just melt the dash plastic anyway.... Thus completely impractical for a blower motor.

 

An electric motor - any electric motor - draws a lot more amps than a high resistance light bulb. This is because electric motors use unductance coils to generate large magnetic fields - those coils have LOW resistance, and thus use large amounts of electrical current. The Subaru blower motors are rated at 160 watts - that's 11.5 amps at 14 volts. To run the motor at half speed you would have to dissipate about 80 watts of power..... Think about how hot a 100 watt light bulb gets - would you want to touch it? That's how much heat your switch would have to dissipate.

 

A dimmer switch simply won't do it - that's why you never see infinitely variable fan speed knobs in cars..... they always have around 4 to 8 discreet speeds. Same reason you don't see infinitely variable speed wipers - it's intermitant (with varying timer settings), and then 2 or 3 discreet speeds.

 

As for the result if you try - it won't blow a fuse or the motor. It will burn up the switch - lots of acrid smoke, if not outright flames.

 

GD