E34 Radiator temperature switch wiring

[ktteoh]

folks, i'm trying to do an electric fan conversion. i would like to re-use the current radiator temp sensor switch (the one at the side of radiator with 3 connectors).

is there a diagram for the 3 connectors and what they are connected to and when they get activated?

[shogun]

page 417 and 418 in the online wiring diagram for 1993 E34.
http://shark.armchair.mb.ca/~dave/BMW/e34/e34_93.pdf

[ktteoh]

shogun, i look at the specs and i'm guessing the 3 connectors are for:

1. ground
3. > 91C
2. > 99C

can you tell me which one is pin (1), (3), (2) from the picture below:

http://www.joetlc.com/images/products/61311378073.jpg

also is there another version that kicks in at lower temp like 75C/85C? - that's more useful for an electric fan activation.


page 417 and 418 in the online wiring diagram for 1993 E34.
http://shark.armchair.mb.ca/~dave/BMW/e34/e34_93.pdf

[shogun]

61 31 8 361 787 Radiator Fan Switch - 3 Prong - 80/88 degree
$33.95
http://www.bavauto.com//assets/product_images/hardpart/61318361787.jpg
The standard one is Radiator Fan Switch - 3 Prong - 91/99 degree
Part # : 61 31 1 378 073 $ 28.95
http://www.bavauto.com//assets/product_images/hardpart/61311378073.jpg
All pics and prices from www.bavauto.com under cooling system auxiliary fan.

Well, you have your existing connector and there you can see how the are connected.

Brown with maybe another color = ground

Connections: when ignition is on

Wires jumpered
Violet/grey and brown, fan runs on low speed

Black/grey/yellow OR Black/grey and brown, fan runs on high speed

Yoy can easily test it, pull the plug, use a plier or something other made of metal and jumper ground with one of the others, then the other one, then you know what high and low is, as you can hear the fan noise at low and high.
I do that always to test the functions.

There is no other switch available, and I doubt whether it is recommendable to have a switch already kick in at 75 degree C.
The engine NEEDS a certain operating temperature, otherwise you will have more wear and higher fuel consumption if the MOTRONIC always 'thinks' that engine is still cold.

[ktteoh]

shogun, you are right on the money. i tested per your instructions and everything checks out.

btw, at what temp does Motronic ECU thinks it is not "cold" anymore?


61 31 8 361 787 Radiator Fan Switch - 3 Prong - 80/88 degree
$33.95
http://www.bavauto.com//assets/product_images/hardpart/61318361787.jpg
The standard one is Radiator Fan Switch - 3 Prong - 91/99 degree
Part # : 61 31 1 378 073 $ 28.95
http://www.bavauto.com//assets/product_images/hardpart/61311378073.jpg
All pics and prices from www.bavauto.com under cooling system auxiliary fan.

Well, you have your existing connector and there you can see how the are connected.

Brown with maybe another color = ground

Connections: when ignition is on

Wires jumpered
Violet/grey and brown, fan runs on low speed

Black/grey/yellow OR Black/grey and brown, fan runs on high speed

Yoy can easily test it, pull the plug, use a plier or something other made of metal and jumper ground with one of the others, then the other one, then you know what high and low is, as you can hear the fan noise at low and high.
I do that always to test the functions.

There is no other switch available, and I doubt whether it is recommendable to have a switch already kick in at 75 degree C.
The engine NEEDS a certain operating temperature, otherwise you will have more wear and higher fuel consumption if the MOTRONIC always 'thinks' that engine is still cold.

[shogun]

at what temp does Motronic ECU thinks it is not "cold" anymore?


no idea, depends probably on the engine type. For example the M60/M62 8-cylinder run or require very high temperatures.

But as a rule of the thumb you can take the temperature when a thermostat opens..

[ktteoh]

shogun, i never did get a time to tinker with this idea till recently.

i still plan to do the fan clutch delete & replace with an electric fan system in situ. i plan to use a 2nd temp switch to control the electric fan cutover.

question is where to put the 2nd. temp switch - i remember shogun publish somewhere a picture of the 2 different cooling circuit paths in the M50 engine block.

i plan to identify the correct hose, split it in half and connect a straight iron coupling with socket for screwing the switch in.

so which hose should i insert it in for closest accuracy to engine temp?
Cooling System Water Hoses BMW 5' E34, 520i (M50) (http://bmwfans.info/parts/catalog/E34/Sedan/Europe/520i-M50/RHD/M/1993/october/browse/engine/cooling_system_water_hoses/)

item #1
item #2
item #6 [near the lower of the two #7 outlet - one connected to bottom of radiator]


my thought is that it should be in #1 since that's where the hot water from engine comes out once the thermostat opens up?

[ktteoh]

shogun, i never did get a time to tinker with this idea till recently.

i still plan to do the fan clutch delete & replace with an electric fan system in situ. i plan to use a 2nd temp switch to control the electric fan cutover.

question is where to put the 2nd. temp switch - i remember shogun publish somewhere a picture of the 2 different cooling circuit paths in the M50 engine block.

i plan to identify the correct hose, split it in half and connect a straight iron coupling with socket for screwing the switch in.

so which hose should i insert it in for closest accuracy to engine temp?
Cooling System Water Hoses BMW 5' E34, 520i (M50) (http://bmwfans.info/parts/catalog/E34/Sedan/Europe/520i-M50/RHD/M/1993/october/browse/engine/cooling_system_water_hoses/)

item #1
item #2
item #6 [near the lower of the two #7 outlet - one connected to bottom of radiator]


my thought is that it should be in #1 since that's where the hot water from engine comes out once the thermostat opens up?

[shogun]

sorry, I am not familiar with the M50 engine