As part of a stock brake overhaul, I'm replacing my old rusted 914/4 master cylinder with a new 19mm unit. Weird thing is the new sending unit only has one electrical connection instead of the two from the original one. Inside the rubber connector boot there are two brown wires, one with a white stripe and one without. Wires were disconnected by a PO long ago judging by the outstanding rust build-up on the old sending unit terminals.

Questions:

1. Which wire do I connect; the one with the stripe or without?

2. What do I lose if I run with only one sending unit wire connected?

Many thanks in advance.

There are 2 wires because the original switch required a ground connection. The new switch grounds through the body of the switch to the cylinder. Connect the brown/white, leave the brown off ( its the ground wire) and it will work exactly as it should.

it's the brake malfunction light in the dash,

Exactly what I needed to know. Thanks much to you both.

Exactly what I needed to know too! Thanks guys.