The Stovebolt Site Forums The Shop Area The Electrical Bay white (brake light switch ground) wire in turnswitch

what is the purpose of the brake light ground wire being in the turn signal switch?
i put a power plus 13 from American auto wire in my 1963 c10.
i did use the old harness from the gauge panel otherwise all new wires and switches.
my issue is that when the you signal a right turn, the lights work correctly except there is no dash light indicator.
when you signal left, you get nothing except the dash light indicator on steady.
I'm stumped

rolf

Rolf my guess is since it is not always a guarantee the steering column will provide a good ground they add a ground wire to be sure you have one. As for the other question (no dash light indicator yet right turn lights work correctly) my first guess would be maybe a burned out turn signal bulb, turn signal bulb holder not making good ground (twist it a bit and see if it starts flashing) or somehow a wire that should go to it didn't get tied in correctly. Hard to say without seeing it. The left signal problem sounds like sort of the same thing...turn signal switch is sending out power but for reasons unknown it isn't making it to the wiring for front/rear turn signals.

I had to delete and redo becasue I always look at my GMC diagrams.
I don't have a 1963 Chevy truck wiring diagram, but generally......

1. There are no grounds running into the turn signal switch. Lamp grounds are handled by chassis metal "return" path.
2. The T/S switch is a "router" sending power to bulbs.
3. The T/S needs the brake lights run thru it so it can turn off the brake light signal to either left or right, so that the bulb blinks, because stop and turn use the same filament.
4. The turn indicator bulb is wired/"tapped off of"/"spliced into" the front left and right turn signal wires.
5. I see a white wire 17A, it is a power wire to output of brake switch.

Once these are double checked, let us know the problem. Don't count on the old harness being correct or the new harness being installed without a few errors.... and of course grounds are always a source of electrical troubles. Dozens of grounds needed by all bulb sockets, et al. Most grounds are "intimate contact connection". Just touching more or less. Some are bolted/screwed. Sometimes there is an actual ground wire. Maybe headlights, horn, dome, dash metal, tank sender...... As said, burned out bulbs will cause some weird issues.

The chassis and the body being most of the ground, as time passes,, corrosion, rust and fatigue sets in all over the place. Bad grounds are a headache to find/fix.

To add a bit of clarity, the brake switch is being grounded through the taillight bulbs via the column connector.

The brake switch connects +BATT to the column where it passes through the turn signal switch and is routed out to the taillights. It is then grounded through the bulb.

Did the turn signals work before you replaced the harness? Do you have a multimeter (or ohmmeter) to check the wiring inside the column?

Edit: Out of curiousity, are you running LEDs or incandescant bulbs? How is the brightness of the dash indicator to the right vs the left?

And also some aftermarket turn signal switches do have a ground wire. Mine does and the poster is installing a non-original device, so I can't say whether it does or doesn't. If you happen to have a model like one of the Grotes with right/left blinker bulbs and an emergency flasher bulb built into the unit none of those bulbs will work without ground. In the model I have, if any bulb fails to work or if it loses ground all the bulbs in that chain won't flash until the problem is solved. The instructions were clear on this point, also.

thanks for the replies
i'm running incandescent bulbs.
i had issues with the dash lights and the high beam indicators i fixed those by adding 3 ground wires to the dash indicator box. i put grounds all over, engine to frame, frame to cab, cab to engine, all back to the battery
the dash indicator harness came with the truck with the truck. no other wiring. it was a roller when i got it.
the 63 has only one dash turn signal indicator light. both left and right are wired to the same bulb holder. when the right turn is on it doesn't even light up when the left is on it burns steady. not the brightest but you can see it ok.
the turn signal bulb holder is plastic so is the generator, oil pressure, and the hot and cold lights. only the dash lights and hi beam indicator have metal bulb holders grounded to the box.
currently the bed is off the truck. based on what is mentioned above do i need those tail lights in the circuit in order for the blinkers to work?
i can wire up a house no problem but automotive wiring is the bain of my existence. i've been shown a few times how to work a multimeter but as soon as it's just me and the meter i can't get that thing to work.
not an excuse just a freakin fact. i do use the heck out of my test light though.
i have a complete dash harness out of a 65 truck and i use i as a reference.
the wire colors in the aa harness, the 65, and turn signal harness are the same. i also have the 63 truck manual the 60-66 manual and a couple other wire diagrams. i've triple checked all the circuits.
i'm thinking i either have a bad signal switch, a bad bulb holder, or the truck is possessed.
it's a neat little truck, short bed fleet side. i put in a 283 with an m20 behind it.
thanks again
rolf

If the dash only has one light, how do you have it connected to the harness?

Typically you would have two bulbs connected to the two indicator wires. If you connected those together, tou have shorted the front turn signals together and both of them will flash at the same time.

A single indicator should be wired between the flasher and the steering column connector so that it flashes with either signal, but doesn't short them. Alternatively you could connect the two indicator wires together with diodes to prevent back-feeding power.


Can you give us a simple "what bulbs do what in each switch position" to make sure we are on the same page?

Something like:

Turn signal left, brakes not applied:
Front left turn bulb on
Front right bulb off
Rear left brake/turn bulb flash
Rear right brake/turn bulb off
Dash indicator off

Turn signal left, brakes applied:
Turn signal right, brakes applied:
Turn signal right, brakes not applied:
Turn signal center (off), brakes applied:


Also, is the turn signal switch the original one in the column? Or is it an aftermarket one?

How many wires do you have going into the column?

Don't take matching wire color between them to mean they should be connected. ESPECIALLY between the stock wiring and an aftermarket harness.

This could be 90% of your problem. If you give us the lighting list from my previous post, we can go from there.

Use a 3 prong flasher (like a DOT 550). The third prong is marked P for pilot. Hook the single dash indicator to it.

This drawing I did years ago when troubleshooting my turn signals may help. It was from my '57 GMC, but all early GM turn signals (before 4 way flashing lights) that used the same rear light filaments for brake and turn signals worked the same way. Ignore the wire colors as yours may be different.

The top drawing shows switch connections when the turn signal lever is "off", the center drawing is with the lever in the right turn position and the bottom drawing is with the lever in the left turn position. All 3 yellow contact sets move at the same time and direction inside the switch.

i have attached the diagram i've been using.
it's out of the 60-66 manual 63 section (why did they cut of the sheet and section info in that book!)
i verified it with the 63 truck manual.
you can see that the lt and rt indicator wires go to the same bulb.
i do have an after market turn switch. it has the same number of wires as the one shown in the diagram.
yellow is now purple, violet is now yellow, and pink is dark green (or vice versa they go back to the rear rt and lt).
maybe they changed the turn signal switch when they went to separate dash indicator bulbs?
i don't have a 63 switch.
the truck is wired as you see it in the diagram.
i did a frame off 53 3/4ton and i didn't have even half the issues i have with this one(not a frame off).
another beer bartender!
rolf

The only way I can see that this could work is if the original turn signal switch INTERNALLY ...

a. provided a ground where the 20-DBL (20 gauge Dark Blue) wire connects while the turn lever was signaling a left turn and flashing the 20-LBL (20 gauge Light Blue) wire.

b. provided a ground where the 20-LBL wire connects while the turn lever was signaling a right turn and flashing the 20-DBL wire.

c. provided the same voltage (either 12v or [more likely] ground) to both the 20-DBL and 20-LBL when the switch is in the center (no turn) position.

What would happen is that voltage would switch directions through the single turn signal lamp on the dash depending on which direction you were signaling. As long as one side of the lamp wasn't grounded this will work. All the other dash lamps show a ground, but the turn signal lamp DOES NOT.

Pictures below are of your wiring diagram with a little color added to make it easier to trace the wires in question.

By the way, this should answer your original question "what is the purpose of the brake light ground wire being in the turn signal switch?"

That is an interesting schematic.

So a new question: is the American Auto Wire harness a 63 specific? Or a universal?

You said that the truck matches the schematic, but you also said that you used some original harness pieces and I just want to clarify what you are working with.

the aa harness is the power plus 13. it is one of their universals.
the wiring instructions withe the pp 13 pretty much match the color code and schematic for the chevy truck.
they do say they don't use the hot light test wire from the ignition switch to the dash light.
everything else is what you would be working with to wire the truck correctly.
it's really a pretty simple electrical system. that's why i stay with the older trucks.
it's also what makes this issue so frustrating.
i am inclined to agree with bill in that, old pre two dash indicator light bulb sockets, had a turn signal switch that is different than the two socket systems.
now i just need to find one to check it out
i will post what i find out when i find a switch.

thanks for all the help.
rolf

So what you have is a hybrid between part of the schematic and part of the universal.

How are at reading schematics? I don't want to be condescending, but I also don't want to assume anything.

Based on you statment that you have the stock dash harness, I think the right side of the first image is factory and the left side is new. Is that correct?

Bill's highlights show the output side of the wiring, but not the inputs to the turn signal switch.

Can you tell us what all the lights do with the switch in different positions?

Can you also tell us exactly what aftermarket switch you have? Make/model/number/etc?

My theory is still that either the switch is miswired or the switch is bad. If you can give us the info on it, we can help look at it further.

The wiring diagram shows what I think is a 2 prong flasher plugged into the fuse box. If GM had used a 3 prong flasher they could have had a less complicated turn signal switch (assuming I am right about how the switch supplies ground for the dash turn signal lamp) as well as using a standard one wire lamp socket for the dash turn indicator.

It almost sounds to me like your replacement turn signal switch does not do the job of the original switch. If that is the case and if a proper switch is not available there is a solution to this problem.

1. Cut the Dark Blue and Light Blue wires a couple of inches from the indicator lamp socket.
2. Add some wire to the Light Blue wire still attached to the socket. The other end of this wire needs to connect to ground.
3. Acquire two 1N4001 diodes. They are cheap. $5 for a package of 100 on Amazon. I probably have a few in the garage if you need them.
4. Twist the NON-stripe end of the two diodes together and also twist the Dark Blue wire from the lamp socket into this bundle. Apply solder.
5. Solder the loose end of the Dark Blue wire to the stripe end of one diode.
6. Solder the loose end of the Light Blue wire to the stripe end of the other diode.

Oooooooooooooooooooops! I forgot to tell you to put heat shrink tubing over all bare wires.

I just completed my wiring on my 54 GMC and the brake light is wired through the turn signal like this schematic. It is a hot wire for the brake lights and not a ground. This allows you to run use the turn signal wires as brake wires and you do not have to run a separate or dedicated brake wire. The wiring harness I used said that it was up to a 54, but the schematic and the way it was wired was for a 53 and earlier with a dedicated brake wire. The turn signal bulb was off the flasher, one bulb. The switch then controls the light for brake or turn signal so you loose the brake light on the bulb with you have the turn signal on.

I agree that is how the stock '54 switch (and later until at least '59) is Mike. The switch in the schematic the OP posted must play an additional function to provide the single indicator lamp on the dash while using a 2 prong flasher.

Myself, I would ohm meter (continuity) check the switch to see how it functions. Without a ground on the switch itself in the schematic, it has me scratching my head.
I used a new universal wiring harness wiring with an old 60s Napa switch. 51 didn't have a dash indicator, so I drilled and welded in a spot on the speedo opposite the hi beam light. Used a metal single wire bulb housing.
And like bill has said, diodes to iliminate reverse voltage from switch that isn't just like original to single dash bulb. I found a pre-made dual diode harness for incandescent motorcycles. 2 in from left and right and single out to dash bulb. It was about $10, but already has leads and heat shrink. I think it is called 'motorcycle single turn lamp indicator diode'.

Rolf,
Wire it per the diagram you posted using color or function as a guide. I don't see a need for any added components like diodes....or anything special to do. I believe diodes/feedback are an LED thing.

This is pretty simple. I am writing this "book" becase I see you are frustrated and are getting down. We have all been there. So a complete explanatioin is a cool down and hopefully give you the whole picture to feel confident and keep your good effort and thoughts going. I have probably repeated some of what Jon G, Bill and others have already said. We are all trying to scope in on the general procedure and info to give you.
Typically, using a universal harness, you use the truck wiring diagram, the harness instructions, aftermarket component wiring instructions, Stovebolt.com, a test or two...so that a few things get adapted to allow the kit to be "universal" and accomodate the situation. ALl in all this is a pretty basic new harness rewire. I don't think I, my self, would use the old dash wiring but I can't see it from here. Not that the wire may not be good. but PO's do a lot of sketchy wiring..... and you have reported some troubles under there.

1. If a aftermarket turn signal has a built-in indicator bulb, the bulb is grounded to the case of that turn signal switch. So the case needs to be grounded to the column which is part of the chassis ground system. Clamp needs to touch the column metal or an extra wire.
2. If you have a dash mounted bulb in a socket, that socket needs to be grounded to the dash so that the bulb case gets grounded to chassis.
3. The switch provides a flash signal to left and right, front and rear bulbs. Those bulb sockets need ground at the socket, by touch or a wire, so that those bulb cases get grounded to the chassis.
4. The front flash signals used for the dash indicator are the DBL (Dark Blue) and the LBL (Light Blue) on your diagram as you know, or their AWA equivalent per instructions.. Both get connected to the dash indicator bulb input terminal on it's socket. A plastic socket probably has stick out metal ground clips that contact the metal hole.... or may be a two wire socket.

So basically it's all there, just needs sorted, wired and grounded. You know what you are doing. You are doing good. Make SURE you test all the bulbs at the battery to be sure they are all good. You should be doing wiring at the last of your build when all lights and body parts are assembled and mounted on the truck. If for some reason you need to test this stuff now, you will have to set up a "test set" to simulate the lights or you are going to get all screwed up. With a simulation, you won't know if all the chassis grounds and sockets are grounded on the truck sufficiently. I advise getting the truck and components mostly all together/mounted before wiring.

AAW Harness: Most of the harness will work as instructed. As far as the turn signal goes, These types of universal kits include a GM column connector to fit an original turn signal plug OR to adapt to an aftermarket switch. The instructions for the Power Plus 13 show the colors they use, the circuit number and the description words for the function of each wire regarding turn signal. So wire your aftermarket to the blank mating half of the connector included in the kit, accordingly. You don't necessarily need a 3 prong flasher, I believe you have a 2 prong already in the Power Plus fuse panel. Wire the 14B and 15B to the one dash bulb you have. Wire 14A and 15A per instructions. You can leave the 4 way flasher wires disconnected. If the aftermarket switch has a built-in indicator bulb, you can abandon that also if you want to.

At first, just poke the proposed wire stripped ends into the AAW wired connector half to test. Then either install them into the blank connector half they give you or just butt splice them and forget the connectors. All you need is an ice pick voltage tester if wire is powered or a continuity test if not powered, to trace each wire. Use the buzz/sound feature on your multimeter for continuity. Some wires for the T/S switch may come from the AAW harness (17A). AAW is just running some thru a fuse, that's basically all they are doing.

As you move forward, please give us one issue at a time as it happens and wait for a reply to that issue before getting too deep.

Typically if a bulb stays lit, and is supposed to flash, it's a bad flasher or flasher circuit or wrong flasher or wrong voltage flasher.
If a bulb flashes fast, there is a bulb out somewhere usually.

In general: The mechanical type flasher is not a relay, no ground to it. It is a switch, a bimetalic switch with a heat coil in it, not an eltromagnetic coil. Heat coil heats a bimetalic strip which bends and straightens to connect "X" to terminal "L" or connect to "L" and "P" and provide flash. L and P are the same thing more or less. You can use a two or three prong. If you use a 2 prong, "L" will provide the flash. In your case you have the flasher all set up in the AAW panel. A 2 prong flasher can sometimes cause a bulb to glow. If a pilot bulb glows or dims between flashes, change to a 3 prong.


1. Please explain 'box" and "dash indicator box". What exactly do you mean?
2. I don't know what brand and model of aftermarket T/S switch you have to help with wiring that.
3. "i will post what i find out when i find a switch". What switch are you finding and what is it for?

gentlemen
here's what i have discovered.
i looked up the gm part number i got from the assembly manual it turns out the the 63 switch was a 63 only.
well, 63 to early 64, then the part number changes twice for the rest of 64.
in my box of electrical stuff i found a switch with the 65 colored wires, and another one that has a completely different set of wire colors.
i scraped the insulation to see if the wire colors were surfaced bleached but it is white all the way through.
i found numbers on both switches and googled them. one is a 64 the other a 63.
if you look at the photos you can see they are different. how exactly they work i don't know.
i have located 63 switches that are identified by the 63 part number but i am not sure yet that they are the "real deal" they are pricy.

the "box" i referred to in my post is the dash lights/speedo box. sorry, i should have explained that better.
the switch i'm looking for is a 63. part number 8981967.
the switch i have in there now is from either classic parts of another of the venders.
thanks
rolf

7 wires, but only 6 of those round tubes inside the switch??? I assume one wire hooks to each "tube".

OK, Box= the gauge cluster. Thanks.

I asked about what switch, I got confused. You said "I have an aftermarket switch and no 63 switch", so I thought you were all set to use the aftermarket and wondered what other electrical switch you meant. I got it now. You want a 63 switch. Thanks.

Whatever switch you use, aftermarket clamp on, original, etc...the wiring is fairly easy to figure out by buzzing. A 7th wire could be horn.

Here is probably the 63 you found. I know of no reason to think it's not the real deal. Good vendor. I use all the time. Don't know if a one year only, hard to find switch, can be pricey. (now-a-days). I think your post has been sorted?
Click Part No. 53-507A (QE quality?) and there is a 53-507 (reproduction?) for $15 less. They are both "reproduction". Different colored wires?

i ended up getting a 63 switch from pro steering column.
put it in and i have everything working.
thanks to everyone that helped me.
until the next issue.......
rolf

Good times.