Question on Wiring Auxillary FAN

#1

Hope everyone had a great holiday. Taking a bit of time off and thought it might be good to start a little prep work before the start of the season. I had ordered a electric fan and was looking at how to wire it. From what I can tell of what was left after removing the AC condensor and fan assembly four years ago, there are two electrical leads in front of the radiator. One has power when I jumper the low speed circuit from the radiator temp sensor and one has power when I jumper the high speed circuit.

Any reason I shouldn’t just connect these to the new fan? The Bentley book says they the low speed activates at 196 and high-speed at 210.

Shouldn’t this work just fine? I know some have wired into a switch where they cut in on/off manually. I’m a little concerned that I might forget to turn it on until I see steam coming out of the front!

Also, what’s the feeling about timing belt replacement. I replaced TB along with water pump in my first season or 4 years ago. Not a lot of miles just time. OK or replace as preventative maintenance? Thoughts?

Can’t wait to see the new and improved CMP…

Keith

#2

While you could use the low-temp thermoswitch to turn on the fan, that switch doesn’t close until 91C which is really a bit high. 80-82C thermoswitches are available and would be a better choice. Having a manual override is kind of nice in that you can anticipate a need for the electric fan and manually engage it.

In street use the timing belt should be replaced every 6 years or 60K, as I recall. I think that’s too long on a track car that sees a lot of time above 4000rpm. Given the consequences of a timing belt failure, once a year isn’t a bad idea. The belt is pretty cheap.

#3

OK how does this sound as an idea.

Wire a switch on the dash which when ON will provide Positive to the same wire as the LOW lead on the radiator thermoswitch. That way if I want I can cut it on manually, but if I forget, the thermoswitch will turn on. This way I can use the existing relays? Does that sound like it would work?

Also on the thermoswitch does anyone know if the High Speed/high temperature activates, it deactivates the low speed circuit. I assume so. The original Aux FAN had a big resistor which I assume was the way to get the low voltage/low fan speed.

Sorry, not an electrical engineer by trade.

Thanks for the feedback.

Keith

#4

Let me tell you how I did mine - don’t know if it will help or not…

I used the existing fan in front of the radiator (but I assume you will use a different fan - but use the same wiring I did). I bought about 3 bucks worth of BMW brackets from BMW for it. I took the 2 wires going to the fan and spliced them together, so it always runs at high speed. Now it turns on when the thermostat turns it on, or when I hit the A/C button on the dash (as that is how the stock system works). So - I have a fan that goes on if I forget to hit the switch via the thermostat, or if I do remember to turn it on via a switch. Very simple - no messing around.

I don’t know about the rules/spirit of the rules - I don’t know if it is legal to change the thermoswitch - Could be considered part of the fan, which is free, or not. Just something to consider…

#5

nobody would protest an alternate temp thermoswitch - it is part of the fan control mechanism and hence lumped in with the fan allowances.
cheers,
bruce

John Black wrote:

[quote]Let me tell you how I did mine - don’t know if it will help or not…

I used the existing fan in front of the radiator (but I assume you will use a different fan - but use the same wiring I did). I bought about 3 bucks worth of BMW brackets from BMW for it. I took the 2 wires going to the fan and spliced them together, so it always runs at high speed. Now it turns on when the thermostat turns it on, or when I hit the A/C button on the dash (as that is how the stock system works). So - I have a fan that goes on if I forget to hit the switch via the thermostat, or if I do remember to turn it on via a switch. Very simple - no messing around.

I don’t know about the rules/spirit of the rules - I don’t know if it is legal to change the thermoswitch - Could be considered part of the fan, which is free, or not. Just something to consider…[/quote]

#6

I like that idea, but I think my AC switch is long gone…I’ll have to see if I can find it.

Other option is to use the switch that was for the rear window defroster. It has a light that works when it is depressed. Only problem is the switch has like 8 terminals and I don’t have a wiring diagram in Bentley of this. Anybody have the wiring for this switch?

Keith

#7

you can look at the ETM (on left side menu, click on Links, then E30 Resources) and deduce what the various terminals on the switch do.
cheers,
bruce

#8

Replace the radio with a blank (from BimmerWorld), then run an external switch:

…Cool shirt switch is the one to the right.

#9

Craig - sweet, clean setup.

Keith, I know this is in a previous post, but I would still look at the option of running an aftermarket fan relay with or without a thermostat. The aftermarket fan may pull more amps than the original accessory fan risking frying the wiring. If you can find an original AC switch, the yellow wire is one you want to tap in to. The relay is easy to wire - and you can access power from the distribution block on the passenger side of the firewall under the hood. I just turn mine on on the grid and flip it off when hitting the track. If you see steam on the track, the fan is not going to save you.
Ed

#10

That is a BMW part - I’m sure Bimmerworld sells them too, but any dealer/part place has them.

64-11-1-368-515 for $9.60.

#11

The BMW dealer here looked it up and said it is no longer available. I’m going to find someone aftermarket that has one.

John