Electric Fan swap relay?

[magnus77]

Hey guys,

Im swapping from my fixed radiator fan to an sn95 electric fan and I cant for the life of me figure out which fan controller I need. The fan has the ground, low, and high wires. So do I get a double fan controller to accommodate the high and low settings? It's going to be automatic temperature based relay, not a manual fan switch that some mustang guys seem to like.



Cheers,

Gerhard

[DerekTheGreat]

Cool, going to be following this thread lol. Wish I had info for ya but do not. I was watching Hot Rod Garage and the episode was of them building a POS '79 Camaro, I think this is the fan they recommended as it moves a ton of air and doesn't draw ass loads of power. They had a schematic of the relay wiring up there but nothing about an actual relay itself, which is what I'd also want to know as I want to do it just like you are. No switch funkiness but also to wire it so it comes on when the A/C is running.

[sly]

That fan requires that the low speed feed be cut when the high speed is enabled or it will burn up the fan. That's why I didn't want to use the 90s fans in my 93 when I shoved the F150 radiator in it. The 2-wire fans with a resistor block for the low speed are much easier to deal with and don't have the issue of burning up if low and high are both lit up. What you can do is set up a relay to power the low speed through the NC connection on the high speed relay. That way when the high speed kicks, it cuts power to the low speed. Then you can use any dual speed controller.

like this:


Of course, using this method, you could just use a dual speed fan switch/sensor to control the mess and not even dick with a "controller"

[DerekTheGreat]

Nice. You must work with electronics or something haha.

[sly]

It's like I've done this before or something. I would have liked to do this on my current setup, but the 70A relay doesn't have the center (NC) leg. Meh... 2-wire fan with resistor block, not needed for my application.

Also, yeah... I'm an electronics engineer. Car wiring is easy for me to understand... but I still don't like fixing it. I do still like the older cars as they can actually be fixed instead of just "replace that module" and get wallet raped.

[magnus77]

Yea, I might see what my local store has for dual speed controllers. I didnt realize it required two speeds when I bought it. Lack of research on my part haha.

[87gtVIC]

Sneaky relay wiring! Me likey.

[His Royal Ghostliness]

Not the only way that can be wired either. You could key-on feed both #86s, then use the high-speed #87a to feed low-speed #30. This way even if low-speed relay shorts itself between 30 and 87 (had it happen, damn water/humidity) the fan motor will still shut off properly cause power is cut to low-speed #30 entirely.

Edit: the only benefit of a proper "controller" is to slowly ramp up the current to the motor, so you don't get a large spike when she kicks in (especially on high speed). If the motor isn't a power-hungry bitch and the relay is big enough and the fuse is of the MAXI (slow-blow) type you can get away with the simple on-off temp switches just fine. No need to involve electronics when simple electrics can get the job done just as good.

[gadget73]

The cheap controllers don't ramp either. They just turn things on and off. Thats sort of the gain with the resistor low speed method, its current-limited so you don't have that massive inrush of current.

Honestly I fixed all of my electric fan problems with a clutch fan. I got tired of the noise, the electrical surges, and the temperature swings. The one time that the relay failed and caused the motor to overheat and blow a coolant hose in a drive through was pretty much the last straw. The stock fan went back on and its been rainbows and sunshine ever since.

[sly]

I had to go to a e-fan in the 93 because the higher revving PI motor keeps blowing out the fan clutch. I said screw that noise. Replacing that thing is more of a bitch than I care to dick with. e-fan and done. Though the initial wiring was a little bit of a bitch, I don't have to touch it now.

[sly]

Here's the better relay wiring that HRG was talking about:



the low and high switch can be taken care of by using a dual temp fan switch (looks like a temp sensor). Part number 61311378073.
http://www.rockauto.com/en/catalog/b...an+switch,4312

You'll also need the pigtail to plug into the switch. Most likely find in a junk yard.
You might be able to get one from a dealer, but I would imagine the prices would be steep.

List of models that use that one:

BMW 318I 1991-1995
BMW 318IS 1991-1997
BMW 318TI 1995
BMW 325 1987-1988
BMW 325E 1987
BMW 325ES 1987
BMW 325I 1987-1995
BMW 325IS 1987-1995
BMW 325IX 1988-1991
BMW 525I 1989-1995
BMW 530I 1994-1995
BMW 535I 1989-1993
BMW 540I 1994-1995
BMW 635CSI 1986-1989
BMW 735I 1988-1992
BMW 735IL 1988-1992
BMW 740I 1993-1994
BMW 740IL 1993-1994
BMW 750IL 1988-1994
BMW 840CI 1994-1997
BMW 850CI 1993-1997
BMW 850CSI 1994-1995
BMW 850I 1991-1992
BMW L6 1987
BMW M3 1988-1995
BMW M5 1988-1993
BMW M6 1987-1988
BMW Z3 1996-1997

[His Royal Ghostliness]

What's the thread on that BMW switch tho? I seem to recall running into one like that when I did my e-fan swap on the small devil fuel beast, and the thread on the switch was something weird... Temperature triggers do seem good tho, 196F low speed and 210F high speed.

[sly]

sorry... 14x1.5 (metric)

also, I would probably use one of those adapters you put in-line on a radiator hose.

[magnus77]

I think this guy did what you guys are describing: http://www.gmtruckcentral.com/articles/markviii.html

[pantera77]

Honestly I fixed all of my electric fan problems with a clutch fan. I got tired of the noise, the electrical surges, and the temperature swings. The one time that the relay failed and caused the motor to overheat and blow a coolant hose in a drive through was pretty much the last straw. The stock fan went back on and its been rainbows and sunshine ever since.

I had one fan controller die in traffic and leave me stranded.
I had one switch die in traffic and blow my rad.

I switched back to a mechanical fan and magically all my problems were gone. No more of that electric BS for me.