BMW M3 E30 Dual Temperature switch replacement
Aux fan is controlled by a dual temperature switch which is located in the thermostat housing. Switch has two switches in it, slow speed is operated at 91C and fast speed at 99C. Code for the switch is 61311378073.
I had some doubts that my switch is not functioning correctly, so I ordered a new one. I tested the switch by heating it with a heat gun. For some reason it only worked at one speed. I compared the switches and switches look little bit different. I also tested both switches by measuring the resistance on the bench and this revealed why the new one worked only at one speed: Swiches were different, see following table how new one and old one compare. What makes it even more confusing is that ETM connector drawing, page (8500-3) is incorrect for the new switch:
These are the pictures in ETM:
This is how it should be:
Problem is that pins 1 and 2 are not in correct place in the connector drawing.
Next problem is that switches are different internally. See following table how switches operate:
|
Old Switch, continuity between |
New switch, continuity between | |
| Slow speed | Pins 3 and 2 | Pins 1 and 2 |
| Fast speed | Pins 3 and 1 | Pins 1 and 3 |
NOTE: Pin numbers are according to the corrected drawing.
So, in order to use the new switch, I had to swap pins 1 and 3 by opening the connector and swapping the pins. After swapping the pins both speeds worked fine.