Electric fan size and installation pictures

[silasmoon]

76 desmogged. 

[xr4tic]

7 hours ago, silasmoon said:

76 desmogged. 

 

Looking at the wiring diagram for a 76, there should be a green/white striped wire coming off fuse 12 that was for the emissions stuff.

[RMBaiada]

chargin,

 

Can you tell me where you got the Thermo switch (manufacturer/part number), the temperature setting of the switch and the thread size?

 

I have the same drain plug on the side of my radiator as well.

 

Michael

 

 

[Swiss 2002Tii]

On 7/4/2019 at 3:57 AM, silasmoon said:

I have a fan wired up in this configuration I am pretty sure - although it stays on even when the car is off. My guess is that the thermal switch needs it power supply changed to switched power vs battery. Thoughts on how to achieve this?

Silas,

The center connection in this 3-way connector has an unused switched +12V.  It is fed by a green/white wire, which tells you that is fused, coming from the fuse box.  You can use this to power the coil of a relay

 

 

It's a good idea to use the switched power for the relay coil (in line with the thermal switch), and a separate, beefier cable with its own (30A) fuse for the fan power, as it pulls a fair bit of current.

Here's a universal drawing that somebody condributed on the forum:

 

 

[silasmoon]

My fan operation is continually very temperamental and I'm wondering if I'm burning out relays... 

 

I didn't add the diode as proposed in that diagram. The relays still "click" and I've replaced and tested the fan and thermo switch separately. 

Edited June 1, 2021 by silasmoon

[silasmoon]

Huh... Realizing that my original wiring is completely different from the one above. I'm reconfiguring it to match the one Swiss 2002 posted. I realize a relay is just a magnetic switch, but based on Swiss' suggestion mine seemed... strange. 

[jimk]

1 hour ago, silasmoon said:

I didn't add the diode as proposed in that diagram.

You are on borrowed time before the switch goes.  Been there before the above diagram was known.

[silasmoon]

I have some diodes from the days I made guitar effects pedals. Do you just solder it across the leads? 

[jimk]

Yes, I located the diode right at the relay, but it doesn't matter.

 

For info to help why the fan is running where is the sensor located and what sensor are you using?

[Bruce Gennette]

About the diode ...

Electric motors have big coils of copper wire to create a big magnetic field to interact with some permanent magnets to spin the shaft.  (Old style has the coils on the shaft with carbon brushes to transfer electricity to each coil as they line up with the brushes, modern 'brushless' have the coils around the case with electronics switching the power to each coil in turn).  When the power is switched off the magnetic field does NOT go away instantaneously, it does collapse quickly, BUT, in doing so it drives a high voltage spike backwards through the relay and switches.  Not good for them.

A reverse mounted diode gives the electrical spike an easy bypass back to the battery where it will be harmlessly absorbed.  If there is no diode then the surge will create and sustain an electric arc across the contacts of the relay (or a switch) as they are openning and this can/will A ) create a layer of insulating oxide on the contacts or B ) weld them together.

If your 12V fan motor has 10A through it at power off then an approximate  100V x 100A spike will be produced for ~0.1s.  The relay contacts can handle this ~100 times,  a 4A diode can take this several hundred times, a 10A diode will take this punishment forever.

bye.

[Swiss 2002Tii]

Hal Boyle's diagram is spot on.  I mostly do my own electrical work, but when I did mine, I found that by the time I bought all of the components, I could buy a controller circuit from JEGs for about the same.  The controller has a small tube sensor that you push into the radiator fins to detect the temperature.  I did the same on my E9.

I used a simple bracket like Chargin to mount my 12" SPAL (pusher) fan.  Works like a champ, nice steady water temp, even in stalled traffic!

[calw]

More about the diode...  There are DIN relays available with diodes already built in.  BMW P/N  1 373 381 from the days of the E30 will do the trick

 

[silasmoon]

Coming back here again, as my dioded switch fried awhile back, and I bought 5 replacements, but couldn't be bothered to solder more diodes to those switches. Then duh - I realized they probably made some with diodes already as @calw stated, and what was written on the diagram above (albeit very small). 

 

I have been using these Hella switches. 

 

 

Hella makes some Relays with double diode suppression:

 

but the diode orientation is slightly different from the old metal one you linked above, but it is the same as this later five pin that @jimk mentioned in another fan relay thread. Curious if this Hella 003437101 would work too? 

 

[calw]

That should work electrically.  One diode is in the same position in the schematic diagram- from 85 "pointing to" 86.  The other diode is in the 85 leg instead of the 86 leg, but it's pointed the same way, from positive to negative.  DON'T reverse the polarity of the 85 and 86 connections and you should be fine. 

 

 I haven't confirmed your physical pinout - checking the circuit numbers against physical pins.  I thought that was standard via DIN but you need to check it.