Wiring in e-fan/SPAL to stock fan connector

[bennyfizzle]

I've searched, and found lots of helpful threads, but none of the situations I came across were quite the same as mine. I'm wiring in a spal-like 16" pusher and have deleted a/c, the stock aux fan, and have the full fan delete.

The spal obviously just has a 'hot' 12v wire, and a ground. The stock harness has a low-speed, a high-speed, and a ground.

If I were to wire the low-speed and high-speed together with the fan's hot wire, would that run the fan appropriately, per the stock aux fan?

I don't have a bentley in front of me, but I believe the stock system is rated for 30 amps? All of the spal's except the 'high power' ones are rated under 25amps from what I've read. Will it come on at the same speed for low/high? This is a 1993 318i harness by the way.

Thanks for any help.

[VaTechE36]

I would wire it up with both 12v sources from the fan speed temp switch like what you are saying and try it out.

I have mine hooked up to a dedicated switch, but am debating switching over to using the stock wiring so I don't have to remember to turn the fan on.

Good luck!

[bennyfizzle]

Thanks, worst case scenario it pops the fan fuse, right? worth a shot.

[Mike S]

Yes, if you're using the factory wiring be sure to wire it to both or the fan will only function when the one it's wired to is active.

If you wire it to the high temp lead, the fan will come on so late that it won't be able to control the heat. If you wire it to the low temp lead and the fan can't keep it in that range, when the high temp circuit kicks in the fan will shut off.

Trust me - use both, or run a dedicated circuit for it.

Mike

[MasterKwan]

The way it's wired stock only one of those wires is hot at a time. The high speed relay feeds power to the low speed relay when it's NOT active and when the high speed activates, the low speed is disabled. Jumping the wires together should be fine.

I'd wanted the fan to come on full speed at 195 which is why I jumpered the wires together at the thermo switch. Jumpering the wires together that AREN'T brown will basically make it only run high speed. That means the high speed fan will come on at 195. I also ran a switch to the same wires so, I can turn the fans on high speed with a switch but, the stock thermo switch still works if I turn my switch off.

When I'm on track and they throw the checkered, I reach over and flip the switch on for the cooldown lap. I turn it back off when I go back out on track again next.

[tetice]

You can also create a two speed operation like the factory setup by simply adding a power resistor in between low speed power wire and the fan. The high speed power wire would still connect directly to the fan. My SPAL draws far less than 25 amps which makes this feasible. I chose either a 4 or 5 ohm resistor aiming to drop about half the voltage across the resistor. For my particular fan, this dissapates about 10 watts in the resistor. I had a 15 watt power resistor so it can handle it. Picking the resistor can be done by trial and error depending on how much air flow you want. Just make sure that the resistor is rated to deal with the resulting power. The resistor will get fairly hot so make sure it is mounted to something that won't melt easily.

Disclaimer: while this is a reasonable setup for a race/track car where the fan only gets occasional use, I would not recommend this setup for a street car. In my case, the 50% headroom on the power resistor would not yield long term reliability.

Disclaimer #2: I am not sure the SPAL fans are really designed to run on less than 12 volts but I have not seen any ill effects from mine in 3 or 4 years of use.

[savage217]

Just use the high speed wire. I used an alternator extender

Like that and it will work great. I just cut the stock spal connector off and stock aux fan connector and wired that in and it works flawlessly. I also have the low temp aux fan switch.

[bennyfizzle]

It would only come on at the high-speed reading if you only wire to the high speed wire...

[savage217]

It would only come on at the high-speed reading if you only wire to the high speed wire...

I forgot to mention you are supposed to swap the high and low wire so that the high speed will come on when the low speed is supposed to come on.

[bennyfizzle]

swap it where?

[savage217]

You just swap the high and low speed wires on the aux fan plug (the plug that has 3 wires).

[MasterKwan]

Or just tie them together as I suggested so, either switch turns on high speed mode. It's the two wires that aren't brown. Brown is ground.