Emergency Brake Wire

[kansasc10]

I installed a new harness from Painless Wiring, but not sure where to connect the e-brake wire. Should I just terminate it and leave it disconnected? As far as ive always known there isn't a light or sensor on a 72C10 to say "hey dummy, you left the e brake on". Just want to make sure I don't get a brake light coming on the dash if I leave it disconnected.

[VetteVet]

It's not an emergency brake wire, it goes to the combining valve by the master cylinder and when the fluid in either side of the master cylinder is low, a switch in the combining valve grounds the wire and turns on the light in the dash. If you ground the wire to the master cylinder with the key on the light should come on and it You turn the key switch to the start position the light should also come on.

Here's a picture of the wire on the switch.

[kansasc10]

Thanks vet. I already have that one hooked up to the master cylinder under the hood. The wire in question is in the cab coming out of the fuse box labeled emergency brake it's a tan wire just like the one under the hood. Painless has it numbered 981 and the one going to the master cylinder is labeled 975 if that helps.

[Steeveedee]

It goes on the switch on the parking brake mechanism. I hope you are younger than me. I have the devil of a time getting that pretzelized to get in to look at it, these days.

[VetteVet]

Originally Posted by kansasc10

Thanks vet. I already have that one hooked up to the master cylinder under the hood. The wire in question is in the cab coming out of the fuse box labeled emergency brake it's a tan wire just like the one under the hood. Painless has it numbered 981 and the one going to the master cylinder is labeled 975 if that helps.

I have read several threads on the 67 to 72 trucks and they all say that there was no brake switch on the emergency brake. Painless may have added the wire to include later models. The painless manuals I see, label the wire as a tan 18 gauge wire for the prop valve and their no. shows 970 as the wire number.

If you want to add a switch to the E-brake you can mount brake switch on the E-brake pedal mount and ground one-side and run the other side to the wire going to the prop valve. This 981 wire you speak of may already be tied into that wire and all you need is the switch.

I will take another look at the painless manual and see if the 981 wire is listed.

[kansasc10]

I took a picture of my manual but can't figure out how to load. I think you're right it's there for someone who has a switch on their ebrake pedal. I have no such switch that I can see. The wire is 12 volt switched according to my meter.

[Andy4639]

Originally Posted by VetteVet

I have read several threads on the 67 to 72 trucks and they all say that there was no brake switch on the emergency brake. Painless may have added the wire to include later models. The painless manuals I see, label the wire as a tan 18 gauge wire for the prop valve and their no. shows 970 as the wire number.

If you want to add a switch to the E-brake you can mount brake switch on the E-brake pedal mount and ground one-side and run the other side to the wire going to the prop valve. This 981 wire you speak of may already be tied into that wire and all you need is the switch.

I will take another look at the painless manual and see if the 981 wire is listed.

This is what I did on my 71.
Here is what I did and why.

http://67-72chevytrucks.com/vboard/s....php?p=7608320

[jocko]

I did this to my 66 (different parking brake arrangement than the 68 and up, but same theory as what Andy posted).
http://67-72chevytrucks.com/vboard/s...d.php?t=419932
But I connected it to an unused light tube (Tandem Lock, a med duty light in a C10 that is unused) - changing the red lens text to indicated what I wanted. Something like that could be done in a 67-72 also if desired. But, if wiring into the existing brake light circuit, probably nothing worth re-printing, so - if you're moving and NOT stopping, then it means you've lost half your brakes - and if you're having a hard time moving PERIOD, then you have your parking brake on!

Andy - did you splice into the brake light circuit (so that you could get either indication, park brake or hyd circuit fail) or did you replace it (i.e. choose park brake indication instead of the hyd circuit fail indication)? (I need to re-read...)

[Andy4639]

Originally Posted by jocko

I did this to my 66 (different parking brake arrangement than the 68 and up, but same theory as what Andy posted).
http://67-72chevytrucks.com/vboard/s...d.php?t=419932
But I connected it to an unused light tube (Tandem Lock, a med duty light in a C10 that is unused) - changing the red lens text to indicated what I wanted. Something like that could be done in a 67-72 also if desired. But, if wiring into the existing brake light circuit, probably nothing worth re-printing, so - if you're moving and NOT stopping, then it means you've lost half your brakes - and if you're having a hard time moving PERIOD, then you have your parking brake on!

Andy - did you splice into the brake light circuit (so that you could get either indication, park brake or hyd circuit fail) or did you replace it (i.e. choose park brake indication instead of the hyd circuit fail indication)? (I need to re-read...)

I spliced into the brake wire. If it's on it's either the E-brake is on are you have brake problems.
My 64 SS Impala is factory wired like this. I'm going to do dad's 56 like this also.


Mine with the speed hut gauges.



The switch mounted and grounded




Factory setup:

[kansasc10]

Originally Posted by Andy4639

This is what I did on my 71.
Here is what I did and why.

http://67-72chevytrucks.com/vboard/s....php?p=7608320

Thats crazy your brake lever just fell off like that! Thats a new one to me.
Got my wire harness completely installed. I needed one last switched power wire to wire into my nos solenoid switch so I used the extra brake wire in question since it was the last wire I had to terminate. After seeing what you did with the ebrake switch though, I think I might use it for that instead. Everything is working great except for one minor detail.
(I can post this in a different section if I should) when I switch on my headlights and all the gauge bulbs light up on the dash, the brake light on the fuel gauge has a very very faint glow to it. It looks to me like its bleed through from the other lights, barely glowing through but Im not a fan of how it looks especially at night. Are you guys able to see your brake light shining at all when you turn your headlights on? Ive checked all my grounds and connectors...the blinkers, brake lights, headlights, radio, hazards, horn, everything else is working great. I have ground straps going from the engine block to the cab, the frame to the inner wheel well, frame to the cab, cab mount to frame and block to the frame. I checked the headlight grounds going to the rad support, and the grounds on both side marker lights behind the lens. I wire wheeled around the ground locations to get down to shiny metal. All are tight and have star washers. I disconnected the brake wire from my nitrous switch and capped off the brake wire to rule that out but it didnt change anything.
The gauge cluster connector (#6 pin I think?) is grounded under the dash to clean metal. When I turn my lights off, the glow completely disappears. I can only see it with the lights on and like I said, its really faint, only slightly visible during the day but more so at night.
If its bleed through, I guess Ill just have to live with it but cant imagine GM wouldnt isolate it somehow. Its like its getting a really low level of voltage, just enough to BARELY make it glow. Not sure what to try next if anything.
If it matters, my fuel tank was moved to the rear and the sending unit has a good ground to one of the cross members.