Okay, what is this for?

[R8rPhan]

As I was removing the existing wiring harness in preparation for a rewire, I came across this.. Doesn't appear to have been hooked to anything.. There was a couple wires taped to a rubber hose that when through the firewall, and on the cab end terminated in some sort of switch.. The hose goes right into the switch, but the wires appear not to..

The (vacuum?) switch is white and mounted right next to the brake pedal...

There are three wire connectors in the bundle.. The one on the engine side of the firewall has a blue wire and green wire going into it... The hose isn't connected to anything, just sealed off with a bolt in the end...

Inside the cab there was a pink wire plugged into the fuse box with it's own connector, and coming out of the little harness at the same point, was a connector that was factory pinned to the bottom of the steering column strap that holds the steering column to the dash with a blue green and brown (brown could have been purple, hard to tell)...

and then the other connector was the brown (or purple) going up into the dash a couple feet towards the passenger side, and had it's own connector.. as far as I can remember, this wasn't attached to anything either... I tried to label everything as I took it apart, and I can find nothing in the harness now removed or the AC harness still in the truck that has a connector that mates to it...

Anybody have a clue what all this is for? There doesn't seem to be anything that will mechanically push the white button on the swtich...


Also on the brake light switch, there was an additional pair of connectors (besides the ones for the brake light) sticking off the back of the switch (towards the driver) with nothing connected to it... Is that by chance for cruise control? I don't currently have CC, but plan to add it later... So that would be hand if that's what it's for...

 

[R8rPhan]

Also there was a brown wire coming from the power brake proportioning valve (mounted on the frame near the radiator)..

Don't currently have power brakes, but the cab has the bolt pattern that says it came with them, and I also have the booster/master cylinder off of a donor 88 suburban that I plan to install to have power brakes on the truck..

So I want to make sure the valve has whatever electrical it needs...

Anyone, have any idea what I should supply power to this with? Is it full time 12v, or is it switched by something? If so, what? How much current does it draw? (I'm using a generic EZ wire harness for the rewire)

Is the switch in the above post in any way related to that valve, or the brake system?

 

[Keith Seymore]

Cruise?

The switch near the brake pedal could be the one that kicks off the cruise control when braking. The control unit on early squares was mounted on top of the driver's wheelhouse.

K

 

[R8rPhan]

Cruise?

The switch near the brake pedal could be the one that kicks off the cruise control when braking. The control unit on early squares was mounted on top of the driver's wheelhouse.

K

So, is the extra pair of contacts on the brake switch to notify the cruise control that the brake has been pushed?


Any idea about the wire on the proportioning valve?

Thanks,
Mark

 

[Keith Seymore]

The wire on the prop valve is the one that turns the light on in the cluster in the event of a partial brake failure.

If you shuttle the valve inside the prop valve (or combo valve, in this case) as the result of a fluid leak in one half of the hydraulic system then it grounds the circuit and turns on the light.

K