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03-21-2017, 09:12 PM | #1 |
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Location: Alberta, Canada
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Brake warning lamp issue
The brake warning lamp is coming on and staying on with the headlamps on. The light does not come on at any other time.
With the headlamp switch in the off position or the park lamp position the lamp is not on. The lamp only comes on with the headlamps on. I would assume if it was a short to ground somewhere in the wire to the from the warning lamp switch to the ignition switch or from the ignition switch to the warning lamp bulb it would be on at all times. Any ideas?
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1967 C10 SWB Stepside 1977 GMC Jimmy 2WD 2015 Camaro ZL1 Instagram @sqclcustoms |
03-21-2017, 10:02 PM | #2 |
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Re: Brake warning lamp issue
Just on with low or high or both beams? Might be ground problem in headlight circuit.
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03-22-2017, 09:57 AM | #3 |
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Re: Brake warning lamp issue
I will check into this. The only wiring done on the truck over the winter was to replace two wiring harnesses. Direct replacement harnesses and all plugged in so no splicing was done. One harness from the cab to the rear lamp harness that runs the length of the frame and the rear tail lamp harness.
The one thing I notice is that the left rear tail lamp had never been as bright as the right rear. Have tried new bulb but it did not fix it. Not sure if this can be related. Bad ground at the lamp? Haven't touched any other wiring all winter
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1967 C10 SWB Stepside 1977 GMC Jimmy 2WD 2015 Camaro ZL1 Instagram @sqclcustoms |
03-22-2017, 10:00 AM | #4 |
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Re: Brake warning lamp issue
Lamp is on with high beams or low beams.
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1967 C10 SWB Stepside 1977 GMC Jimmy 2WD 2015 Camaro ZL1 Instagram @sqclcustoms |
03-22-2017, 10:31 AM | #5 |
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Re: Brake warning lamp issue
Simple. The brake light switch is a ground activation circuit.
I would disconnect the switch under the hood and see if the light goes out. If it does then the head lights are some how grounding through the brake switch wire. If you have everything working other than this one issue take a look at the back side of the ignition switch. Then the fuse block. The brake switch light on the dash runs to the ignition switch then to the fuse block then out to the switch on the brakes. It maybe shorting in the ignition switch plastic connector (those are bad about melting) theen the fuse block. Per the drawing I posted. Is the temp gauge acting funny it's right beside the brake switch on the ignition switch connector. It's a ground also. http://67-72chevytrucks.com/vboard/s...185856&page=16
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1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
03-22-2017, 11:40 AM | #6 |
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Re: Brake warning lamp issue
I'm still stymied as to how applying power to the headlight circuit could complete the ground circuit for the brown brake wire. That's the problem, they're two different types of circuits. So leaking power from the headlight switch to the brake light wouldn't do anything. And turning on the headlight switch doesn't create a ground potential anywhere. So weird.
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
03-22-2017, 11:55 AM | #7 | |
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Re: Brake warning lamp issue
Quote:
We have no idea what he has yet! It maybe he needs to disconnect the brake switch and see what happens.
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1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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03-22-2017, 01:08 PM | #8 |
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Re: Brake warning lamp issue
Lamp stays on with the wire to the warning switch disconnected
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03-22-2017, 01:29 PM | #9 |
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Re: Brake warning lamp issue
Tail light does sound like ground problem at Mount point (bolts thru light assembly) . What was the other wires replaced?
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03-22-2017, 01:33 PM | #10 |
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Re: Brake warning lamp issue
Just for giggles,try grounding the brake switch wire with a test light. Both without an with lights on/off
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03-22-2017, 02:04 PM | #11 |
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Re: Brake warning lamp issue
Just for fun, next time it happens, stomp on the brake pedal REALLY hard and see if the light goes out.
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1972 C/10 Cheyenne Super SWB. Restored, loaded, slammed. 1968 C/10 50th Anniversary LWB. Unrestored, stock, daily driver/work truck. RIP ElJay RIP 67ChevyRedneck RIP Grumpy Old Man |
03-22-2017, 02:18 PM | #12 | ||
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Re: Brake warning lamp issue
Quote:
Quote:
The headlights are switched on the positive side and the brake warning light is switched on the ground side. There may be a wiring mistake on the cluster plug that would give a ground to the BW bulb when the dash lights are on. Otherwise I don't see a connection between the BW bulb and the headlight switch other than the dash lights.
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VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative. |
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03-22-2017, 03:03 PM | #13 |
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Re: Brake warning lamp issue
There should be no path to ground for the brake warning bulb except through Pin 2 on the cluster plug. If you could pull that pin wire then it would isolate the ground to the cluster. This is true for both the light cluster and the gauge cluster. Which do you have?
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VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative. |
03-22-2017, 09:14 PM | #14 |
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Re: Brake warning lamp issue
Is it possible that it's light bleeding thru cluster? I.e. The cardboard tube that isolates the indvidual bulbs in the cluster maybe is missing or damaged? Going out on a lib here. I'm not in front of my cluster to see if this is even possible but thought maybe I'd throw it out there.
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Tyler '57 3100 http://67-72chevytrucks.com/vboard/s...d.php?t=813888 '72 K20 Cheyenne http://67-72chevytrucks.com/vboard/s...d.php?t=662879 ‘69 K10 SWB http://67-72chevytrucks.com/vboard/s...d.php?t=805206 '98 Silverado LT K2500HD ECLB Vortec 454/4l80E: 6" lift 315/75/16's ‘87 IROC-Z all original 50K mile survivor TPI 305 IROC Blue ‘10 Camaro 2SS/RS Aqua Blue Metallic #93 -version 2.0 |
03-22-2017, 10:20 PM | #15 |
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Re: Brake warning lamp issue
Vett both the brake light wire and the head lights come off the ignition switch harness also right? They could be contacting each other in between some place. Maybe even in the plastic connector on the key switch itself. I had to replace my once due to over heating and melting of the plastic. I never did find the cause but it's never done it again since I installed the new connector.
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1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
03-23-2017, 01:09 PM | #16 | |
Msgt USAF Ret
Join Date: Jan 2005
Location: Kalamazoo, Michigan
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Re: Brake warning lamp issue
Quote:
According to the wiring diagram, the feed wires for the key and headlight switch are separate wires although they both connect with the engine bay wire from the alternator battery junction. Look in the middle of the diagram where the red wires join. One to horn relay, one to ignition switch, one to the fuse box, and one to the headlight switch. All connected at the junction with the wire from the engine bay. This one shows the red power wires to the key switch (top) and the headlight switch (bottom right). If we could post both diagrams together and line up the wires it would be much easier to see. Ignore the black arrows they show the accessory wire to the fuse panel that powers the wipers,heater fan switch and turn signals. The brake warning light is just an open circuit to ground, and it must be grounded for the light to come on. If it gets shorted to a positive wire then the light won't come on because there is 2 positive sources on each side of the light, and no current can flow through it to light the filament. This is how the charging light works in the idiot light dash. If there were another power source to the light on the brown wire side, when the key was turned to start, the brown wire would become grounded and the light might illuminate, but the other power source would go directly to ground, and we know what that means. Your ignition switch connector probably melted because of a large amp draw through it over a long period of time. That's why the factory went to the relays instead of running all the power through the ign switch. If we get some answers from the OP we'll know more about what's wrong.
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VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative. |
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03-27-2017, 11:09 AM | #17 |
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Re: Brake warning lamp issue
Agree we need more info from him.
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1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
04-01-2017, 09:40 AM | #18 |
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Location: south jersey
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Re: Brake warning lamp issue
Any luck yet?
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