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Brake lights quit...... #971840 Sun Sep 15 2013 03:23 PM
Joined: Jun 2008
Posts: 1,199
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Spotbiltxo Offline OP
Shop Shark
So, a friend told me that the brake lights on the '50 weren't working. Went out to attempt to find the source of the problem and started with the brake light switch. I noticed that the PO had rewired it and it only had ONE wire plugged in to the switch. The original cloth covered wire harness with two wires going to the switch was hanging close by. I took off the one wire and put a new connector on it after cleaning it up well. Put it back on and the brake lights still do not work. My question is should there be one wire or two connected to the brake switch? I know "modern" wiring sometimes allows only one wire (such as a one-wire 12V alternator) but I'm wondering if one of those old wires wasn't connected to the other side of the switch and somehow got disconnected. Could the PO have rigged it so that only one wire is needed on one of the two posts on the switch? If there's supposed to be two wires then there's the source of my problem!!! Any help would be appreciated.

P.S. I bench tested the brake light switch and it's good.


Chuck
1950 Chevy 1/2 ton (original)
1951 Chevy 1/2 ton (future streetrod)
1941 Chevy coupe
1938 Chevy coupe streetrod
Re: Brake lights quit...... [Re: Spotbiltxo] #971850 Sun Sep 15 2013 04:36 PM
Joined: Aug 2010
Posts: 756
G
GWWirth Offline
Shop Shark
You need both wires. One side needs to come from the battery. It may come from a fuse first or from some other positive power component from under the dash. The other side of the switch goes to the break lights. Then the shell of the lamp holder goes to frame or the negative of the battery. It is common to have bad negative because of corrosion.

Re: Brake lights quit...... [Re: Spotbiltxo] #971851 Sun Sep 15 2013 04:48 PM
Joined: Apr 2008
Posts: 703
F
Forty9 Offline
Shop Shark
Brake switch should have 2 terminals. Power is supplied from the light switch to 1 terminal. When pedal is pushed terminals connect and power is sent to brake lights. Check for power from the light switch to brake switch and check continuity from brake switch wire connector to brake lights. I see you may also have a fuse involved.
http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm1203.htm


Ed
Re: Brake lights quit...... [Re: Spotbiltxo] #971971 Mon Sep 16 2013 01:30 AM
Joined: Jun 2008
Posts: 1,199
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Spotbiltxo Offline OP
Shop Shark
I checked the fuse box on the fire wall and both fuses were good.
Honestly I've never studied the wiring into the brake light switch because the lights always worked. I guess one of the two wires coming out of the old cloth covered wiring harness should go to the other post, so I'll make a guess which one and try. If that doesn't make the lights work I'll try the other wire. I'm totally ignorant of all things electrical, so I just have to learn by trial and error.

Thanks for the advice!!


Chuck
1950 Chevy 1/2 ton (original)
1951 Chevy 1/2 ton (future streetrod)
1941 Chevy coupe
1938 Chevy coupe streetrod
Re: Brake lights quit...... [Re: Spotbiltxo] #972006 Mon Sep 16 2013 11:21 AM
Joined: Apr 2008
Posts: 703
F
Forty9 Offline
Shop Shark
Remember that you are looking for voltage, with the key on, coming from the light switch to the brake switch. If no voltage coming to the brake switch you'll have no brake lights. Use a meter or test light to check from the connectors on the cloth wire to ground for 6/12V. Just be sure key is on. Electrical in these old trucks not too involved!


Ed
Re: Brake lights quit...... [Re: Spotbiltxo] #972045 Mon Sep 16 2013 03:32 PM
Joined: Jun 2008
Posts: 1,199
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Spotbiltxo Offline OP
Shop Shark
Fourty9, thanks for the reply. I'll try hooking up one of the two wires in the cloth loom after using my meter to determine which one. Thank you all for helping me. I know nothing about electrical.


Chuck
1950 Chevy 1/2 ton (original)
1951 Chevy 1/2 ton (future streetrod)
1941 Chevy coupe
1938 Chevy coupe streetrod
Re: Brake lights quit...... [Re: Spotbiltxo] #972087 Mon Sep 16 2013 07:11 PM
Joined: Jun 2012
Posts: 1,724
S
Steve_H Offline
Shop Shark
Just an idea you can try.If you have two wires that might be the brake lights then run a jumper from the "hot" wire at the switch to one wire and then the other. If one lights the brake lights that is the one to put on the switch. If the fuse goes then you have a short and you need to find it and fix it. If nothing happens with both wires add a ground from the tail light housing to the frame and try again. If it works then just hide the ground wire and smile.


Steve H
Re: Brake lights quit...... [Re: Spotbiltxo] #972225 Tue Sep 17 2013 12:46 PM
Joined: Jun 2008
Posts: 1,199
S
Spotbiltxo Offline OP
Shop Shark
Thanks a lot Steve. That's a good idea to use alligator clip wires to find the hot wire. Will save a step.


Chuck
1950 Chevy 1/2 ton (original)
1951 Chevy 1/2 ton (future streetrod)
1941 Chevy coupe
1938 Chevy coupe streetrod
Re: Brake lights quit...... [Re: Spotbiltxo] #972257 Tue Sep 17 2013 04:13 PM
Joined: May 2005
Posts: 6,086
B
bartamos Offline
Master Gabster
You should invest in a ice pick test light. Very cheap. "Ice pick" end touches suspected hot and wire with alligator clip attaches to any good ground. (or vise versa). Tells you a lot, real fast. No meter to read, just a light in the handle of pick, comes on if hot is present. $3
There is now a similar, cheap, ice pick continuity tester with a light-up signal. $4.50.


Laziness is the Father of invention.



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