How to wire my fans?
 

Today I put slim fans on my radiator.

Problem:
- Fans each have two wires -- red and black.
- MSM connectors have FOUR wires per fan!! - red, black, yellow(-ish), and greenish/blueish with black stripe.

So I connected the red to red and black to black. I have no idea if this is correct, or if my fans are working at all, etc.

The stock wiring diagram and fans document are on my server:
- http://snarc.net/msm-wiring.pdf
- http://snarc.net/cooling-fans.pdf

Paul suggested that I perform a test by jumping GND and TFA in the engine bay diagnostic box. So I looked at the diag box. The square where TFA should be (third from the right, second row looking from the front of the car) is EMPTY - it doesn't have the metal tabs inside like the other squares do. I had a friend compare this to his own MSM to make sure mine isn't fucked up.

Ergo: HEEEEELLLLLLLPPPPPPPPP!

Ideally I'd like to have both fans on, at all times.

Which gives me an idea: it's one thing to have both fans on at all times when the stock ECU thinks it's necessary to have fans on ...... but is there any value to have both fans on at (literally) all times when the engine is running? If so, then I can ignore the stock fan wiring entirely, and just wire both new fans in parallel to any power source that goes on with the engine. (Can it really be that simple .... ???)

Secondary concern: if it DOES make sense for me to wire the fans using this K.I.S.S. method, then will I get a CEL from whatever nutty method the stock ECU wants to use?

I've got to drive a couple of hours as of 5:00 tomorrow (Wed.) night, so I'd really appreciate some good advice before then.

Find a 12v souce (maybe foglights/headlights) and a ground. It's temporary until you buy a thermal switch.

Link here.

EDIT: This is the "I haz a problem, I needs a fix" way, if you want to avoid CEL's, IDK what to tell you other than find out which wires are which on your OEM connector and use them.

EDIT #2: Couldn't you pull the coolant temp sensor and hold it in boiling water (or maybe hold a lighter up near it) w/ the key in the run position and probe the 4 wire connector to find which one is 12V? They should be sending the signal to run the fans at that point.

Car isn't due for NJ inspection until Feb. 2010. CELs are therefore okay for the next 8 months. :)

Would I cause any harm, or are there any drawbacks at all (early wear-and-tear?) by having both fans on at all times? If not, then why NOT do it for the extra cooling?

PITA during cold weather, otherwise I cant think of any issues with it.

How so? I.E. would my car not warm up quickly enough?

Email from Paul. He says:

"1. It'll take longer for the car to reach operating temp(important when it's colder)
2. Fan motor life will be reduced significantly
3. That's puts an unnecessary load on the electrical system all the time. You actually lose power that way because the alternator kicks on."

Just idle the car, that'll get it hot without the fans. Might take 20 minutes, but it'll happen.

Both fans on all the time isn't really ideal, you could just take all the fan signals, run them through a relay, and have ANY fan on turn them all on.

My idea is take the "slow" speed, have it run one fan, and the "high" speed and have it run both. Very close to stock performance that way.

As to which wire is which - well, I'm nearly too drunk to sit, so I'm not going to look now.

I'm looking at the wiring diagram right now. It appears that they changed the MSM's fan wiring in mid '04, and if the diagram you posted is correct, you have a late '04 car. From that, I see that both fans are in parallel, and the fan motors are set up for two-speed operation.

The yellow wire at the fan is one speed (not sure hi/low) which comes from Fan Relay #1, from the 30A fan fuse. The Grn/Black relay is the other speed, coming from Fan Relay #3 also via the 30A Fan fuse.

The Red wire goes to Relay #2, and curiously, then to ground. I can guess only that they're deliberately shorting the fan's winding to ground when it turns off, possibly to allow circulating current when in free-wheeling mode.

Now, the good news: there is no feedback mechanism that I can see in any of this which would allow the ECU to throw a code for no fans.


I like the idea of having it such that low-speed turns on one fan, and high-speed turns on both. To do this, you'll need one SPST automotive relay rated 20-30A.

I'll post a schematic in just a bit, I need to go to a meeting right now.

Thank you Joe!!

If possible, I'd greatly prefer a schematic showing how to make both fans turn on at the same time.

Kind of moot, but interesting, re: "late" car: according to the VIN decoder, my car was built in Feb. 2004 on the second day of the MSM assembly line. It's only #93 of 4,000.

Forget the dual speed stuff, to complicated. You dont need it. On/Off is more then enough for anyone.

Turn the AC on, if both fans come on then you are done.

Oh, well that's astoundingly easy then. Just connect together the Yellow and Green / Black wires at each fan position and wire them to the (+) terminal of the fan, connect the (-) terminal of the fan to the black ground wire, and leave the red wire disconnected:

http://img33.picoodle.com/img/img33/...sm_2adcdc5.gif


Well, that's coming from a non-Mazda source, so take it for what's it's worth. So long as each of your fans has a four-pin connector with yellow, green/black, black, and red wires, the above will work.

Lame. I like the one fan/two fan idea.

I was wondering, if the OEM fans are two coils, perhaps they ground the other coil to keep one coil from fighting the other when in 'high' power mode.

random thoughts:

1) low speed place the 2 fans in series
2) hi speed apply 12V to both fans

Connecting the 2 fans in series will give you low fan speed but it's sucking through the whole radiator. Running fans in low speed will give you much longer life than one that always runs at hi speed.

+1

There's no way the lack of back-emf from the motors going slower would actually make them hotter that way, is there?

Dual single-speed fans are working now thanks to Joe's schematic. Both fans turn on at the same time which is what I wanted.

Next: I will make a primitive shroud.

.

Wait, you want me to turn you into a shroud? Okay, it's your life. :)

Sigh. This is going to be another one of those things that sounds fun but just ends up hurting....

Tell ya what .... if I make a non-sucky shroud that actually works, then I'll post a how-to .... okay?