Water temp sensor query - 3.0CS

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Deesta

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Hi, I am in the final throws of restoring my 1974 3.0CS and I am doing away with the old 5 blade fan. I have installed an electric fan and the wiring looks straight forward. I have two queries regarding the water temp sensor that sits on top of the thermostat housing.

Query 1: Can I simply divert the current wire to the electric fan relay?
Query: If so, the current temp sensor has a higher activation temp of 120 degrees. Should i just replace this with one with an 82 degree activation.

Thanks.
 
Yes, a lower activation temperature makes sense. I thought the temperature switch would be in the radiator and not the thermostat housing, but it may be even better there.
 
Well I ended up getting a thermostat housing with 5 potential outlets. I need to keep the current sensor as it hooks up to the temp gauge on the dash. I am adding a Tridon TFS110 thermo fan sensor. That should solve the problem.
 
Good call. I would not try to use the existing sensor for both the gauge and the fan. The sensor operates as the ground for the light circuit; as the sensor heats up its resistance is lowered, allowing the needle on the gauge to move upward with the increase in voltage. If you add another load to that circuit, you change the resistance in the circuit and the gauge will not read correctly. Adding another sensor is the way to go. I used a VDO sensor, but it sounds like you found another good option.
 
You will need the temperature sensor switch which is a 2 prong switch. You can find it in the 74 parts diagram. The switch fits on the lower radiator hose outlet on later radiators. There's a bung built in to the lower outlet. It is a thermal switch which creates continuity once it reaches temp. There's a big temp difference at the water devider.
 
I used 90°c and 99°c switches in a multiport thermo housing. They operate a Volvo 2-speed fan control relay and I used the auxiliary fan from an E34 as the cooling fan.
 
Mounted the fans on the engine side. All installed however the fans aren't cutting in. I will need to recheck my relay wiring.
 
Did you wire the sensor in the ground side of the 85/86 terminal circuit of the relay?

Which sensor did you use?
 
Don’t forget your auxiliary fan!
I’m a big fan :) of the 82* (180* f) temp switch installed in the lower radiator neck.
61 31 1 364 272
7 bucks
https://www.carpartsdiscount.com/cooling-fan-switch-auxiliary-82-deg-c.html?3593=528150
I wouldn’t dream of using the original high/low switches for extra cooling.
I think bmw was proven dead wrong on their high/low temp switch choices from the later cars. 99* c on the cold side of the radiator is a disaster.
 
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