What’s this called?

[eaglescout526]

 

That thing that had a connector plugged into it on the prop valve. What is this thing called? 

[Limeyjeeper]

This is the brake fluid level switch.

[eaglescout526]

14 minutes ago, Limeyjeeper said:

This is the brake fluid level switch.

I’ll try googling with this. 

[eaglescout526]

I found it. It’s called the brake failure switch. 

[Limeyjeeper]

Yes because if there is no fluid in the proportioning valve that is what you have!!

[eaglescout526]

22 minutes ago, Limeyjeeper said:

Yes because if there is no fluid in the proportioning valve that is what you have!!

…well yeah….we all have a brain fart now and then. Anyways the parts manual didn’t have it listed as a serviceable part and finding it was tricky. But they’re a Ford part. I really just didn’t want the owners of this ZJ I’m helping them with to buy a new prop valve for the switch. 

[AZJeff]

It is NOT a brake fluid level switch.  It is a brake pressure IMBALANCE switch.  The factory brake system is divided into two subsystems—one for the front wheels, and one for the rear wheels.

 

Basically the switch closes when either of these subsystems have lower brake pressure than the other, which can happen if either system develops a leak.  The switch is very basic, being just a plunger that is activated by a spool valve that shuttles one way or the other when pressure on both sides of the spool is not equal.

 

the switch is common to many vehicles of the era of the MJ.  I would bet ALL  Jeeps of that era share a common part here, along with the Fords that were mentioned.