Electric Fan Knowledge and Schematic Needed

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Ken Wolkens

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Still working on the 1973 with a friend that has undergone a lengthy restoration and have hit a dead end on how the electric fan is controlled.

We have traced the harness for the fan motor back to the passenger side front fender just behind the grille opening radiator (GOR) support. There is nothing there except the heavy gauge wires leading to the fan. After jumping 12 volts to the fan wire we find the motor works perfectly so now we need to figure out what's missing.

FWIW, there are two sensors that are mounted in the right upper side of the radiator side tank that look like temp sensors or temp switches but no wires going to them.

I assume there should be some sort of fan control relay that was mounted in the right front area of the engine compartment either on the fender apron or the GOR but there is nothing there and it also looks as if a few wires have been chopped off.

We have the schematic diagram from eBay and the Haynes service manual but neither of them even acknowledge that an electric fan exists.

Any help, insight or schematics will be greatly appreciated.

Thanks, Ken Wolkens
 
My 72 has no temp sensors in the radiator, it has the thick harness on the driver side so the water temp sensor must be the one in the thermostat.
I know mine works because it came on once on a hot day when idling in place for a while at the shop. In some cases the electric fan is there for the AC
and is turned on when the AC is one. Do you have AC? Mine does not.

Is that radiator the stock Behr radiator?
 
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Ken Wolkens said:
Still working on the 1973 with a friend that has undergone a lengthy restoration and have hit a dead end on how the electric fan is controlled.

We have traced the harness for the fan motor back to the passenger side front fender just behind the grille opening radiator (GOR) support. There is nothing there except the heavy gauge wires leading to the fan. After jumping 12 volts to the fan wire we find the motor works perfectly so now we need to figure out what's missing.

FWIW, there are two sensors that are mounted in the right upper side of the radiator side tank that look like temp sensors or temp switches but no wires going to them.

I assume there should be some sort of fan control relay that was mounted in the right front area of the engine compartment either on the fender apron or the GOR but there is nothing there and it also looks as if a few wires have been chopped off.

We have the schematic diagram from eBay and the Haynes service manual but neither of them even acknowledge that an electric fan exists.

Any help, insight or schematics will be greatly appreciated.

Thanks, Ken Wolkens
Click to expand...

Will this help?
 

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Ken Wolkens said:
Still

FWIW, there are two sensors that are mounted in the right upper side of the radiator side tank that look like temp sensors or temp switches but no wires going to them.Ken Wolkens
Click to expand...


those two sensors IMHO are the ones related to the AC electric fan, they are there for compensating the presence of the AC front evaporator that reduces the flow through the radiator, i know they have two different temp settings to act when the AC is not on but the engine requires the AC electric fan to help, one for each speed
 
Ken,

Are you sure the "two sensors" on the right upper side" of the radiator tank aren't just sealed off connections for a previous auto transmission cooler lines? Is one near the top right side and the other one about 8 inches below it, inline with it? As in this diagram:
11000008_tn.jpg


Does your radiator look like this? Look at the bung on the lower right elbow:
example.com--A171111212962112501-30.jpg


The AC fan temperature switch gets mounted on the lower right radiator elbow, the water output elbow. In this way the fan turns on when it sense the radiator isn't lowering the coolant temperature sufficiently and thus needs additional airflow.

The schematic is in the E9 manual and may the same as posted above. See it here at the bottom of the page.
http://www.e9-driven.com/Public/Library/BMW-E9-Manual/pages/en/64500200.html#refertoc
 
I completely rewired my electric fan so it operates with the a/c on or when the thermo fan switch in the radiator turns it on. I've attached a schematic showing how I wired my car. I replaced the factory electric fan with a Spall hiflow fan and I used 2, 30 amp 5 pin relays. I hope this helps.
 

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This is all great info guys!

Based on the info in the manual link provided I can see that the relay should be where I suspected and the schematics will help me wire in a new one correctly.

When I get back over to his house I'll get a bunch of pictures and get them posted.

Thanks, Ken
 
Luis A. said:
Ken,

Are you sure the "two sensors" on the right upper side" of the radiator tank aren't just sealed off connections for a previous auto transmission cooler lines?
Click to expand...

I wondered the same thing but they are at the top of the tank and on the side meaning the tops of the senders are pointing at the right fender.

I'll get some pics the next time I'm down at his house.

Thanks, Ken
 
Can you post some pics of your fan install and thermo switch - does it mount into the radiator drain plug? Thanks.

DougE said:
I completely rewired my electric fan so it operates with the a/c on or when the thermo fan switch in the radiator turns it on. I've attached a schematic showing how I wired my car. I replaced the factory electric fan with a Spall hiflow fan and I used 2, 30 amp 5 pin relays. I hope this helps.
Click to expand...
 
Stevehose said:
Can you post some pics of your fan install and thermo switch - does it mount into the radiator drain plug? Thanks.
Click to expand...
Love the tropical radiator option. I visualize a Piña Colada on the hood and palm trees lining the white sand beach. Reality may have been a summer in Kabul.

Now I do not know what turns on the non AC electric fan..
 
Stevehose said:
Can you post some pics of your fan install and thermo switch - does it mount into the radiator drain plug? Thanks.
Click to expand...

I'll get those together and post. There was a plug in the radiator below the hose connection, that's where I installed a 320i thermo fan switch.
 
Luis A. said:
Ken,

Are you sure the "two sensors" on the right upper side" of the radiator tank aren't just sealed off connections for a previous auto transmission cooler lines?
Click to expand...

Here's a pic of the radiator and the two sensors/senders I'm referring to.

2ylkb9w.jpg


Any input is appreciated.

Thanks, Ken
 
That is not a stock radiator, it lacks the upper bracket to mount to the radiator wall, instead it has a bolt. My coupe was an auto and has the oil cooler fittings but no temp sensor anywhere. I assumed when A/C is switched on the fan comes on, there is a relay below the coil for this purpose.
 
that radiator was standard in E28 cars, it is not the stock radiator for a coupe,

the two sensors are the ones for the air cond ventilator, each one for a different speeed, slow, fast
 
Ok Thanks guys. That answers the question about the mystery sensors.

I did set up a relay (mounted under the coil on the fender liner) for the fan like the original schematic shows.

Anybody know what these wires might be for? They are black with red stripes and look like they went to something that was mounted above the coil?

addc9h.jpg
 
Really dumb question now...

Knowing what I do about ballast resistors in other applications I think I know the answer to this but here goes.

Is the resistor required on a fuel injected car?

It currently starts and runs.

Go easy on me. These old imports scare me. :-D
 
It looks like you have the old black coil which used a 1.1 ohm external resistor to avoid burning the points prematurely. Blue coils have internal resistor so the external is not needed. Points just won't last as long.
 
Ken - I believe DougE's wiring schematic is incorrect. The relay switching circuit usually runs through the 85/85 pins and the higher amp 12 volt source to pin 30 and then pin 87 to the fan. If I understand the diagram he shows the 12 volts driving the fan running back through the switch and nothing controlling the switching side.
 
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