SPAL aux fan wiring

[Z3eattle]

2000 Z3 M coupe:

Do you think I can directly tie together the stock wiring of the two aux fan leads, thus deleting the low speed resistor, to power a 16" SPAL fan to replace the factory aux fan; or, should a SPAL fan replacement in this context be triggered off a relay?

I'm doing this because the factory aux fan takes up so much room and I am in the process of installing an oil cooler, and eventually an intercooler for a turbo build next winter.

• Current cooling system: Mishimoto radiator/Zionsville shroud with spal puller triggered off low temp circuit of 80c/88c switch using battery power via relay
• Retaining AC and assume 16" spal pusher mounted right up to condenser will suffice as suitable replacment?
• Was planning using this fan: https://www.summitracing.com/parts/s...2048/overview/
• Factory wiring of aux fan is fused as is so perhaps I need not go the relay route?

Any advise or insights greatly appreciated.

Thanks!

[Blacklane]

The only problem I see is that, when the stock high-speed fan relay energizes the high-speed fan circuit, it removes power from the low-speed circuit. If you wire a single-speed fan to operated on the low-speed circuit, which is energized for radiator temp of 91C or A/C turned on, then the fan will turn off when the system switches to high-speed for a radiator temp of 99C.

To do what you need, you will have to somehow disable the high-speed fan relay or short-out the low-speed part of the high-speed relay.

EDIT: I've given this some more thought and I realize that it is not that hard. All you have to do is connect the SPAL fan to BOTH the high- and low-speed wires. It will run on high-speed for either case, since it lacks the low-speed circuit and resistor, but that's OK.

[Randy Forbes]

The only problem I see is that, when the stock high-speed fan relay energizes the high-speed fan circuit, it removes power from the low-speed circuit. If you wire a single-speed fan to operated on the low-speed circuit, which is energized for radiator temp of 91C or A/C turned on, then the fan will turn off when the system switches to high-speed for a radiator temp of 99C.

To do what you need, you will have to somehow disable the high-speed fan relay or short-out the low-speed part of the high-speed relay.

EDIT: I've given this some more thought and I realize that it is not that hard. All you have to do is connect the SPAL fan to BOTH the high- and low-speed wires. It will run on high-speed for either case, since it lacks the low-speed circuit and resistor, but that's OK.

I've been doing it that way for years__so far, no phone calls to say a car has overheated...

[deni2s]

All you have to do is connect the SPAL fan to BOTH the high- and low-speed wires.

Just to low speed is enough, as temp switch on high speed connects all 3 wires together.

[Blacklane]

The temp switch on the radiator does connect all three wires together for high temp (99C), which is useful when installing a new relay for the SPAL fan.

The OP wants to use the existing high-current circuit, which includes two relays in the relay box, one for high speed and one for low speed. When the high-speed fan relay engages, it removes power from the low-speed fan circuit.

[Z3eattle]

Thank you for the replies everyone! Glad to know others have successfully implemented this.

I will go ahead and wire using both high/low speed factory high current signals and see how it goes.

[Migou]

When I installed an electric fan I used a bmw sensor that I installed in the lower rad hoses. I used one of those adapter things. I retapped it to accept the bmw threads. I didn't want to rely on one sensor that would kill both fans if it failed.

[Remotion]

You can fly to look at my Spal fan and electric system. It has 3 different speeds depending on water temp. It does not run often, but on hot weather it will run totally autonomously even when car is turned off and until temp drops under certain limit.

My friend took a pen and piece of paper and came up with it. It has thermosensor, 3-speed switch/Ω-thingy and a relay or two. I have no idea what is the connection even when I have 3 years of electric schooling behind me... But it works flawlessly.

[David9999999]

I've been doing it that way for years__so far, no phone calls to say a car has overheated...

So, simply hooking both high/low speed wires to the single input wire on the SPAL fan does the trick? I'm replacing the stock fan which has developed spinning resistance/noise on my car.