What does this sensor do?

[CEngel]

I found a loose sensor hanging down by the drivers battery. I finally found the place it came from which was a small slot under the master cyclinder (actually in the plastic resivour. The sensor had been out for some time by the dirt on it. I slid it back into the slot but it wont stay. WHat is this for ???

 

[Alan Reagan]

There is one on the batteries for sensing temperture to regulate charge rate. Not sure if it has been moved or not.

 

[rbattelle]

Trucks with a traditional vacuum-assist braking system use a brake-fluid level sensor within the master cylinder reservoir itself.

Trucks with the hydro-boost braking system have no such sensor. In fact, hydro-boosters have no electrical connections at the master cylinder.

If the same brake wiring harness is used for both types of trucks, then there would probably be an unused electrical connector for the brake fluid level sensor on hydro-boost trucks.

Maybe that's what's going on? I haven't checked to see if I also have an unused connector.

Ryan