Brake warning light

Blackwaterforge · Post by **Blackwaterforge** » October 20, 2011, 1:05 pm

I have a proportioning valve on my truck from a 75 F-250.
It has a two prong switch that I assume is the ground.
I also have dash light that will light in the case of a low pressure assurance in either circuit of the master cylinder.
Has anyone installed one of these on their truck?
How can I wire it up so that it comes on momentarily when the truck is cranked like the oil pressure and alt lights?
Thank You!

banjopicker66 · Post by **banjopicker66** » October 20, 2011, 1:11 pm

I just did this.

The proportioning valve switch, as you surmised, is a ground. You will need to run full-time (not switched) power to the center post of the light, and ground the side of the light to the proportioning valve switch to make the proportioning valve switch light it all up when necessary (hopefully never!).
To get the feature you want, which is very wise, you need a ground-at-start point to tap into. Unfortunately the '66 and earlier ignition switches are not setup for that.

The good news is that you can use a '67 - '77 Bronco ignition switch! It is exactly the same in all respects as the earlier ones, with one exception: There is a 4th tab for a mystery electrical connection outside of the big rubber plug that holds all the '61-'66 ignition wires. This one gives a lot of '61-'66 owners fits because it doesn't seem to do anything.
Well, it is the ground-at-start tab, for these lights which were first used in '67 or '68.
After you get your proportioning valve, switch and its light all set up, run an extra wire from this 4th tab to the ground side of the light. This will make it light up when you rotate the ignition switch to START.
Note again, the light must be powered full time, not from switched power, because the ignition switch turns switched power off when at START.

Good news too, is that Advance Auto and others have this switch for about $15.

As for the brake light, harvest one from a '68-'72 truck. It fits in real nice in the dimple above the ignition switch.

Good luck!

bobenhotep · Post by **bobenhotep** » October 20, 2011, 1:12 pm

you want it to turn on momentarily when you crank your truck? is it wired to work properly right now?

bobenhotep · Post by **bobenhotep** » October 20, 2011, 1:13 pm

If it is already wired, I can probably figure it out. that is why I ask. If not, I can probably still figure it out.

Blackwaterforge · Post by **Blackwaterforge** » October 20, 2011, 1:56 pm

Thanks Banjo
I am going to put a instrument panel from a larger truck with vacuum and tach and I wanted to add this light while I was at it.

bobenhotep · Post by **bobenhotep** » October 20, 2011, 3:00 pm

wow I was going to say you could use a bosch 5 pin relay to do that.

banjopicker66 · Post by **banjopicker66** » October 20, 2011, 3:10 pm

bobenhotep wrote:wow I was going to say you could use a bosch 5 pin relay to do that.

I actually thought of that at first, but I was looking for a simpler and easier answer. When I studied the later schematics, I realized the ground was through the ignition switch, and it sorta drove itself from there.
In fact, the answer solidified itself when I saw on Advance Auto's website that the service replacement switch for '61-'66 was the same as the early Broncos up to '77.

Alan Mclennan · Post by **Alan Mclennan** » October 20, 2011, 4:17 pm

Banjo, that needs to be put into Hints and Trick`s, very good info!!

Haus · Post by **Haus** » October 20, 2011, 7:37 pm

Thank you Banjo! My 66 switch is not in the best shape so I may switch in the bronco one at a later time. I used the same proportioning valve on my truck but just pulled off the connector because I thought it ran the brake light and I had something else rigged up for that. Great info.