Brake light short????????????? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

dropthehammer · 07-30-2005, 09:08 PM

Hi, I am still having trouble finding a short in my brakelights. I have the brakelight harness disconnected at the firewall. As soon as the brakelight switch is activated the fuse blows. I have replaced the brakelight switch. I guess it would be safe to say the problem is in the orange or white wire coming off of the brakelight switch plug. I have a wiring diagram, but I am not positive where these 2 wires go. Any suggestions on how to correct or troubleshoot this short,would be greatly appreciated. Thanks in advance, Bryan.

Longhorn Man · 07-30-2005, 09:40 PM

Is there anything wrong with the turn signals? Turn on the turn signal and then hit the brake pedal, see if it blows, check the other turn signal too. If is is still blowing, then pull the wheel and see if you can see it shorting to ground when you hit the brake pedal.

Gordo · 07-31-2005, 09:32 PM

My guess would also be in the turn signal switch assembly. I have seen the small cancel springs break into two peices and end up shorting out the switch. Like Longhorn Man says, pull the wheel and eye ball the situtation.

dropthehammer · 08-01-2005, 12:38 PM

Guys,
Thanks for taking the time to respond. Longhorn Man, you replied to my original post, questioning the turn signals then. I tried what you suggested in this post, and the brake fuse still blows. The turn signals work on the dash(rear harness disconnected at fire wall) . I am guessing the turn signals are somehow tied into the brakelights? P.O. installed a new wheel, and column is sloppy,(upper bearing?) and if this job is like anything else he did I am sure he butchered everything he touched in the column! Anything in particular to look for??? I am from Ohio as well just east of Cleveland, Mentor to be exact. Thanks again. Bryan

71meangreenc10 · 08-01-2005, 01:00 PM

Heres a thought, unplug the turn signal harness at the coloumn and see if it still blows the fuse, yes the brake lights are tied into the turn signal circuit. Hope that helps....

Smitty

mrein3 · 08-01-2005, 01:03 PM

An old timer once told me...

When looking for a short, if it ain't fuel related, put in the largest fuse you got. Then go look for the melted wire insulation.

It works every time.

chickenwing · 08-01-2005, 02:59 PM

Quote:

Originally Posted by mrein3

An old timer once told me...

When looking for a short, if it ain't fuel related, put in the largest fuse you got. Then go look for the melted wire insulation.

It works every time.

Are you kidding? Yeah it will work but how much stuff will ya fry doin it?

Don't know how the turn signals tie into the brake harness without lookin at the diagram but I trust the prior posters experiance. I would pull the brake switch and hook up an ohm meter. One end on the non-powered side the other end to ground. Then start unpluggin connectors till you get no continuity.

dropthehammer · 08-01-2005, 06:30 PM

Alright, I'm goin into the column, first time for everything. If I can't find a problem, then to plan b. Go get marshmallows, back truck out of garage, install copper fuse in panel, watch for smoke. If it catches fire before I find short, roast marshmallows, call 911, call insurance man!!!!!!!!!!

Longhorn Man · 08-01-2005, 09:19 PM

We actually found a faulty part like that the other day at work. Some one said that the 10 amp fuse that kept popping was too smal so they installed a 15 amp....Followed the smoke, and found the problem! (I don't recomend this though)

The tail lights work like a headlight, a high beam and low beam. (so to speak) The low beam is your tail lights, and the high beam is the brake/turn signal. There are only 2 wires going to each tail light... one for high, one for low. When you hit the brakes, the brake light signal (hi beam) has to go through the turn signal first. (Directly after the brake light switch) This way, you can have the left turn signal on, and the brake light on on the right. If you did not do it this way, then when you'd hit the breakes, the blinking light would stop blinking becouse you'd be putting power to the high beam side with the brakes. So even though the turn signal is flashing, there is still power to that side of the light when the signal is in the dark side of the flashing.
Under the dash, and to the left of the column is a horse shoe shaped harness plug, this goes to the turn signal. Unplug it. You'll probably need a small (tiny) flat head screwdriver. be carefull, 35 year old plastic isn't very user friendly. Then, replace your blown fuse, and then hit the brake pedal. If the fuse lives, then your problem is in the column.
In my opinion, since you have a sloppy column, and possably a crapped out turn signal switch, I would take this oportunity to swap out the whole column for a van tilt. The truck columns (straight ones) are crappy by nature, whom ever made that set up was probably sniffin glue that morning, why GM used it up into the early 90's in the P/30 chassis I'll never know...they had much better crappy columns by then. But, the 72 - 81 van tilt (no key in column) is a pretty simple column, and not many problems come from them. Plus, as an added bonus, they are cheap and plentifull in the junk yards. If you can't find one up there, I'm willing to bet I can locate one here. (however, when i say I can find one, they are no where to be found, but if I say i can't find them, I'll spot 4 the next time I'm in the junk yard)

Longhorn Man · 08-01-2005, 09:24 PM

Wait...before we talk easy tilt swaps...what year is your truck again?

07-30-2005, 09:08 PM	#1
dropthehammer Needs Adult Supervision Join Date: Apr 2005 Location: N.E. Ohio Posts: 19	Brake light short????????????? Hi, I am still having trouble finding a short in my brakelights. I have the brakelight harness disconnected at the firewall. As soon as the brakelight switch is activated the fuse blows. I have replaced the brakelight switch. I guess it would be safe to say the problem is in the orange or white wire coming off of the brakelight switch plug. I have a wiring diagram, but I am not positive where these 2 wires go. Any suggestions on how to correct or troubleshoot this short,would be greatly appreciated. Thanks in advance, Bryan.

07-31-2005, 09:32 PM	#3
Gordo Registered User Join Date: Jan 2001 Location: Killingworth, CT. USA Posts: 3,378	My guess would also be in the turn signal switch assembly. I have seen the small cancel springs break into two peices and end up shorting out the switch. Like Longhorn Man says, pull the wheel and eye ball the situtation. __________________ 1971 C10 swb stepside 350/700R4/3.73posi (retired as of 4/22/03) 1998 S10 short bed 2002 S10 Blazer 1942 Oldsmobile 1958 Massey Harris Pony 1951 Wife Killingworth, Connecticut May those who love us, love us, any of those who do not love us, may God turn their hearts. And if God is unable to turn their hearts, may he turn their ankles so we may know them by their limping. A man who works with his hands is a laborer; a man who works with his hands and his brain is a craftsman; but a man who works with his hands and his brain and his heart is an artist.

08-01-2005, 01:00 PM	#5
71meangreenc10 Its a Truck Thing...... Join Date: Dec 2004 Location: Sierra Vista, Arizona Posts: 3,179	Heres a thought, unplug the turn signal harness at the coloumn and see if it still blows the fuse, yes the brake lights are tied into the turn signal circuit. Hope that helps.... Smitty __________________ 71 C10 283/3SPD Full Resto 71 GMC 1500 Sierra Grande http://67-72chevytrucks.com/vboard/s...d.php?t=518599 70 C10 Suburban Former military GSA truck. 72 Chevy Blazer 4X4, Sloppy Jo, Mountain Climber. Wife says no more trucks. http://67-72chevytrucks.com/vboard/s...d.php?t=707378 72 GMC 1 Ton Motor Home, wife said no more trucks until she saw this one. Gen 3 6.0/4L80E 4.10 http://67-72chevytrucks.com/vboard/s...d.php?t=761110 68 GMC Suburban was 3/4 ton, now 1/2.Wife shook her head 71 C30 Wrecker 71 C20 Scott-Bilt As weird as it gets..BB Cheyenne AC Truck 68 GMC Long Stepside. They keep following me home 69 C30 Former Motor Home, Flat Bed time 70 G20 Red-E-Kamp Conversion "I'm your Boogy Van"

08-01-2005, 01:03 PM	#6
mrein3 Registered User Join Date: Feb 2000 Location: Center City, MN, USA Posts: 3,253	An old timer once told me... When looking for a short, if it ain't fuel related, put in the largest fuse you got. Then go look for the melted wire insulation. It works every time. __________________ '70 cab, '71 chassis, 383, TH350, NP205. '71 Malibu convertible '72 Malibu hard top Center City, MN

07-30-2005, 09:40 PM	#2
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Is there anything wrong with the turn signals? Turn on the turn signal and then hit the brake pedal, see if it blows, check the other turn signal too. If is is still blowing, then pull the wheel and see if you can see it shorting to ground when you hit the brake pedal.

08-01-2005, 12:38 PM	#4
dropthehammer Needs Adult Supervision Join Date: Apr 2005 Location: N.E. Ohio Posts: 19	Guys, Thanks for taking the time to respond. Longhorn Man, you replied to my original post, questioning the turn signals then. I tried what you suggested in this post, and the brake fuse still blows. The turn signals work on the dash(rear harness disconnected at fire wall) . I am guessing the turn signals are somehow tied into the brakelights? P.O. installed a new wheel, and column is sloppy,(upper bearing?) and if this job is like anything else he did I am sure he butchered everything he touched in the column! Anything in particular to look for??? I am from Ohio as well just east of Cleveland, Mentor to be exact. Thanks again. Bryan

08-01-2005, 06:30 PM	#8
dropthehammer Needs Adult Supervision Join Date: Apr 2005 Location: N.E. Ohio Posts: 19	Alright, I'm goin into the column, first time for everything. If I can't find a problem, then to plan b. Go get marshmallows, back truck out of garage, install copper fuse in panel, watch for smoke. If it catches fire before I find short, roast marshmallows, call 911, call insurance man!!!!!!!!!!

08-01-2005, 09:19 PM	#9
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	We actually found a faulty part like that the other day at work. Some one said that the 10 amp fuse that kept popping was too smal so they installed a 15 amp....Followed the smoke, and found the problem! (I don't recomend this though) The tail lights work like a headlight, a high beam and low beam. (so to speak) The low beam is your tail lights, and the high beam is the brake/turn signal. There are only 2 wires going to each tail light... one for high, one for low. When you hit the brakes, the brake light signal (hi beam) has to go through the turn signal first. (Directly after the brake light switch) This way, you can have the left turn signal on, and the brake light on on the right. If you did not do it this way, then when you'd hit the breakes, the blinking light would stop blinking becouse you'd be putting power to the high beam side with the brakes. So even though the turn signal is flashing, there is still power to that side of the light when the signal is in the dark side of the flashing. Under the dash, and to the left of the column is a horse shoe shaped harness plug, this goes to the turn signal. Unplug it. You'll probably need a small (tiny) flat head screwdriver. be carefull, 35 year old plastic isn't very user friendly. Then, replace your blown fuse, and then hit the brake pedal. If the fuse lives, then your problem is in the column. In my opinion, since you have a sloppy column, and possably a crapped out turn signal switch, I would take this oportunity to swap out the whole column for a van tilt. The truck columns (straight ones) are crappy by nature, whom ever made that set up was probably sniffin glue that morning, why GM used it up into the early 90's in the P/30 chassis I'll never know...they had much better crappy columns by then. But, the 72 - 81 van tilt (no key in column) is a pretty simple column, and not many problems come from them. Plus, as an added bonus, they are cheap and plentifull in the junk yards. If you can't find one up there, I'm willing to bet I can locate one here. (however, when i say I can find one, they are no where to be found, but if I say i can't find them, I'll spot 4 the next time I'm in the junk yard)

08-01-2005, 09:24 PM	#10
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Wait...before we talk easy tilt swaps...what year is your truck again?



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