I've searched and can't find the answer. Brake light in dash '68 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

whitesswj · 09-06-2010, 10:34 PM

The BRAKE light is on in my dash in my '68 truck. I've got a gauge cluster.
What causes this because the hand brake doesn't have a switch?

Hubscrub · 09-06-2010, 10:35 PM

low fuild in the master cyl.?

**LockDoc** · 09-06-2010, 10:56 PM

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It indicates that the valve in the Proportioning Valve Assembly has actuated. If you look at the valve assembly you will see the wire connected to it. Usually means that one of your brake systems has failed. (front or rear)

LockDoc

cdowns · 09-07-2010, 07:15 AM

yes it's an indication the brake bias is bad at the distribution block// check your wheel cylinders for leakage

**tkeduk8r** · 09-07-2010, 02:53 PM

if you want to have the brake light come on when you have the ebrake come on you can pirate the set up off of an 81-87 p/u and modifiy it to work with either the hand brake (67-68) or the 69-72 foot pedal e-brake....
--Mike

whitesswj · 09-07-2010, 09:27 PM

Our trucks don't sense the level unless it's drained empty.

whitesswj · 09-07-2010, 09:26 PM

Yes, I had a brake line fail but it was on before the failure. How do I reset this switch.

**LockDoc** · 09-07-2010, 10:03 PM

Quote:

Originally Posted by whitesswj

Yes, I had a brake line fail but it was on before the failure. How do I reset this switch.

I think the '68 valve resets itself when you use it if everything is up to snuff. Some of the valves have a manual reset on the front of the valve body. There will be a small rubber cover over it if it has the manual.

LockDoc

whitesswj · 09-08-2010, 12:56 AM

Quote:

Originally Posted by LockDoc

I think the '68 valve resets itself when you use it if everything is up to snuff. Some of the valves have a manual reset on the front of the valve body. There will be a small rubber cover over it if it has the manual.

LockDoc

I'm gonna go look right now

whitesswj · 09-08-2010, 01:14 AM

Mine looks exactly like this one. Minus the Power setup: There is no reset...

**VetteVet** · 09-08-2010, 11:00 AM

If the brown wire that connects to the valve is grounded, it will turn on the light. Pull the wire off and see if the light goes out. If it stays on the brown wire is grounded some where, and if it goes out the problem is in the valve.

whitesswj · 09-15-2010, 12:37 AM

I pulled the wire and the light goes off and stays off.
Yesterday it flickerd before I pulled it. How do i reset that thing? It's driving me nuts...

mrein3 · 09-15-2010, 07:41 AM

Quote:

Originally Posted by whitesswj

I pulled the wire and the light goes off and stays off.
Yesterday it flickerd before I pulled it. How do i reset that thing? It's driving me nuts...

In the part you took the wire off, the bias is wrong. Think of it as a check ball in there. When you lose either the front or the back, the check ball in there slides that way, grounds the wire to trigger the light, and blocks the leakage to that side (front or back) of the system and quite possibly saves your life. Before this safety feature and a split master was put into vehicles you didn't know you had a brake system leak until you hit something.

To reset it you need to:
1. Fix all the leaks.
2. Bleed the system at all four corners.

Check all brake line and brake hose joints and all four wheel cylinders. Any moisture = leak. Once that is all up to snuff, I would at a minimum bleed at each corner until you get clean, fresh fluid out of each bleeder. If the light didn't go out yet it is stuck from having crummy, old fluid in there. You need to gently bang on the side of it and keep bleeding fluid until you can coax it back into place.

Do make sure your wire isn't cracked and grounding some place else.
Don't simply leave it disconnected. I'm guessing that if you disconnected it and it makes the light go out that the wire is fine. You just need to recenter the check ball in there.

**LockDoc** · 09-15-2010, 08:39 AM

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Or replace it...

LockDoc

68K30 · 09-15-2010, 10:33 AM

Your unit looks like it's just a differential pressure switch, it senses pressure difference between the front and rear brake circuits. AMC had a similar switch on the older cars and once the switch was tripped by low pressure in one circuit the switch would remain tripped until it was manually reset even if the pressure was equal in both circuits. To reset the AMC's you had to unscrew the terminal the wire plugs onto, the terminal may be white plastic[nylon] and has a hex head [7/16" or 1/2"] and press on the brake pedal to center the piston in the block then re-install the terminal and reconnect the wire.

Hope this helps
Bill

09-06-2010, 10:34 PM	#1
whitesswj Embrace the Redneck Join Date: Jan 2004 Location: Cabot, AR Posts: 1,334	I've searched and can't find the answer. Brake light in dash '68 The BRAKE light is on in my dash in my '68 truck. I've got a gauge cluster. What causes this because the hand brake doesn't have a switch? __________________ '01 Camaro *Son, you just can't get there from here...*

09-06-2010, 10:35 PM	#2
Hubscrub Cruzin Join Date: Dec 2009 Location: on the road Posts: 2,835	Re: I've searched and can't find the answer. Brake light in dash '68 low fuild in the master cyl.? __________________ Lime Wife's 67https://www.google.com/url?sa=t&rct=...wZEMODaS2d94u8 Back to the Fifties 59 https://www.google.com/url?sa=t&rct=...NAeStpydfrcj_U Proverbs 3:5,6 "Thanks to the Interstate Highway System, it is now possible to travel across the country from coast to coast without seeing anything."Charles Kuralt In memory of our first baby daughter, daddy and mommy love you. Danica Grace 6/26/14

09-06-2010, 10:56 PM	#3
LockDoc The Older Generation Join Date: Aug 2006 Location: Montezuma, Iowa Posts: 25,656	Re: I've searched and can't find the answer. Brake light in dash '68 - It indicates that the valve in the Proportioning Valve Assembly has actuated. If you look at the valve assembly you will see the wire connected to it. Usually means that one of your brake systems has failed. (front or rear) LockDoc __________________ Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 - Last edited by LockDoc; 09-06-2010 at 10:57 PM.

09-07-2010, 07:15 AM	#4
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: I've searched and can't find the answer. Brake light in dash '68 yes it's an indication the brake bias is bad at the distribution block// check your wheel cylinders for leakage __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

09-07-2010, 02:53 PM	#5
tkeduk8r Senior Member Join Date: Apr 2001 Location: Alexandria, MN Posts: 1,462	Re: I've searched and can't find the answer. Brake light in dash '68 if you want to have the brake light come on when you have the ebrake come on you can pirate the set up off of an 81-87 p/u and modifiy it to work with either the hand brake (67-68) or the 69-72 foot pedal e-brake.... --Mike __________________ 63 C20 2WD, 230/SM420/4.11 73K 68 C30 dump truck, 327,SM425,4.56 66K original 68 C10 2WD SWB Stepper, 250/3-tree/3.73 66K.... Wifes 68 Buick Skylark Custom Conv., 350/TH400/2.56 In our family since '79 69 GMC 1500 SWB 2WD, 350/TH350/3.73 posi... 70 K10 SWB 4X4 4-sp,ps, pb, tilt, buckets, console, sliding back window (Need AC parts) WIP 72 Chevy K20 4x4 350/350/205/4.56 donor 72 Vette 350/M21/3.70 posi, triple black and super fast 84 Olds Cutlass Brougham 350/2004r/4.11 was Dad's

09-07-2010, 09:27 PM	#6
whitesswj Embrace the Redneck Join Date: Jan 2004 Location: Cabot, AR Posts: 1,334	Re: I've searched and can't find the answer. Brake light in dash '68 Our trucks don't sense the level unless it's drained empty. __________________ '01 Camaro *Son, you just can't get there from here...*

09-07-2010, 09:26 PM	#7
whitesswj Embrace the Redneck Join Date: Jan 2004 Location: Cabot, AR Posts: 1,334	Re: I've searched and can't find the answer. Brake light in dash '68 Yes, I had a brake line fail but it was on before the failure. How do I reset this switch. __________________ '01 Camaro *Son, you just can't get there from here...*

09-08-2010, 01:14 AM	#10
whitesswj Embrace the Redneck Join Date: Jan 2004 Location: Cabot, AR Posts: 1,334	Re: I've searched and can't find the answer. Brake light in dash '68 Mine looks exactly like this one. Minus the Power setup: There is no reset... __________________ '01 Camaro *Son, you just can't get there from here...* Last edited by whitesswj; 09-08-2010 at 01:14 AM.

09-08-2010, 11:00 AM	#11
VetteVet Msgt USAF Ret Join Date: Jan 2005 Location: Kalamazoo, Michigan Posts: 8,718	Re: I've searched and can't find the answer. Brake light in dash '68 If the brown wire that connects to the valve is grounded, it will turn on the light. Pull the wire off and see if the light goes out. If it stays on the brown wire is grounded some where, and if it goes out the problem is in the valve. __________________ VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative.

09-15-2010, 12:37 AM	#12
whitesswj Embrace the Redneck Join Date: Jan 2004 Location: Cabot, AR Posts: 1,334	Re: I've searched and can't find the answer. Brake light in dash '68 I pulled the wire and the light goes off and stays off. Yesterday it flickerd before I pulled it. How do i reset that thing? It's driving me nuts... __________________ '01 Camaro *Son, you just can't get there from here...*

09-15-2010, 08:39 AM	#14
LockDoc The Older Generation Join Date: Aug 2006 Location: Montezuma, Iowa Posts: 25,656	Re: I've searched and can't find the answer. Brake light in dash '68 - Or replace it... LockDoc __________________ Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 -

09-15-2010, 10:33 AM	#15
68K30 Registered User Join Date: May 2007 Location: Pennsylvania Posts: 99	Re: I've searched and can't find the answer. Brake light in dash '68 Your unit looks like it's just a differential pressure switch, it senses pressure difference between the front and rear brake circuits. AMC had a similar switch on the older cars and once the switch was tripped by low pressure in one circuit the switch would remain tripped until it was manually reset even if the pressure was equal in both circuits. To reset the AMC's you had to unscrew the terminal the wire plugs onto, the terminal may be white plastic[nylon] and has a hex head [7/16" or 1/2"] and press on the brake pedal to center the piston in the block then re-install the terminal and reconnect the wire. Hope this helps Bill



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