ckkrause

I notice that the temp on my new C2 Tip drifted up past the 2nd line and no fan noise. I check the functioning of the fan and both low and high sped were fine. So I checked the temp sensor screwed into the top of the oil cooler and it seems to be an open circuit. I think I read resistance should be above 17 ohms. Does that mean the sensor is bad? If so, when I change out the sensor will I get a flood of oil? Thanks for your help!

Randall G.

Hello,

If your oil temp. only got to the second line, you shouldn't expect your fan to start. The oil has to reach the 9:00 (horizontal) position, maybe a little higher, before the oil cooler fan starts. Its set-point is 212F for slow-speed operation.

When cold, the temp. sensor on top of the cooler will read somewhere between 13-20 K Ohm, varying widely with room temp. At 100C = 212F, the resistance should be 0.9-1.0 K Ohm.

You will only get a small amount of oil if you remove the sensor--nothing a few paper towels can't handle.

As a reference, a pic of the oil temp. gauge:



Best of luck!

MikeF

Just a minor detail...maybe obvious but...if you change the oil temp sensor, do it when the car is cold. When I changed mine, there was not even a drop of oil to clean up. If it were hot, and the thermostat was opened, I doubt that would be the case.

Adrian

Dear Ck,
I think you are confusing yourself. An open circuit means "very high resistance" M ohms and above. 17 ohms is closer to a short circuit. HOWEVER, the temp sensor is a NTC or Negative Temp Co-efficient resistor. As the temperature rises the resistance decreases. From your post I would suggest that your oil was very hot and this resistance is okay. To confirm what you have to do is measure the resistance when the oil is cold and then again as the oil heats up. As long as the oil is flowing through the cooler.
Please do not create problems for yourself. You say the fan speeds are fine. From how I understand your post, this is quite normal operation. I think there is nothing wrong with your 964.
Randall has given you some figures. As long as you are cooling then everything is basically okay. Did the oil temp come down. Only works well when you are moving forward.
Ciao,
Adrian
911C4

ckkrause

Thanks for your replies! I think I was confused by another thread(Cooling Fan Time) that indicated 17 ohms was a limit and it should have said 17 K ohms! Also, my oil temp gauge was above the 3rd mark and not just the 2nd mark! In other words, the indicator got to about horizontal without the fan coming on. Finally, I took an additional reading, upped the scale to 200K and the resistance appears to be around 20K ohms. To make a long story short... what I really need to check is that the cooler is getting warm. Thanks again!

slant911

As I understand it though. You are saying that your temp guage got above the 9:00 position w/out any fan running? If so, that is not right as this is the point at which the fan should kick on.

Adrian

Dear Slant,
The oil temp indicator is driven by a sensor mounted in the engine. It does not show oil cooler temps. This is another sensor mounted in the cooler as we know.
The oil cooler temp to activate the fan is 212F or 100C. The engine oil temp and the oil cooler temp can vary by up to 10C. The indicator is not a reliable indication for working this out. Rough guide maybe. Outside air temp and whether or not you have the engine under cover installed also play roles here,
Ciao,
Adrian
911C4