68 Issues

I am trying to troubleshoot a brake light problem on a 68. Since I have voltage on the white wire at the plug (only if it is not connected), I was guessing that the problem was in the turn signal switch. Today I got a new TS switch and plugged it in without installing it.....still no brake lights. Should the new TS switch be fully functional just being plugged in but not actually installed on the steering column?


Thanks

GDaina

Did you ground it? The ground cable has clip

Peterbuilt

Yes! If the turn signal switch in the column is bad and you plug a new one in outside the column it will work. No wires in the turn signal switch need a ground.

The 68 TS switch connection is half round, the 69 and up is a flat harmonica connector.
This diagram says 68 to 82 but in 68 the WHITE connects to BLACK w/White stripe.


Compare to 69 and up:


Do you have a 68 column and correct TS switch?

68 Issues

Yes it is a 68 column and the new switch fits. It has the flat harmonica connector with an adapter that goes from flat to the semi-round connector. With the new switch plugged in the signal and hazard lights work but still no brake lights....just like with the old switch. Since the signal/hazard lights work I am assuming that the problem is not after the TS switch.

Since I have voltage on the white wire at the connector (only when the connector is unplugged) with the brakes applied I was thinking the brake light switch was working but now I'm not so certain..hmmmm!!??

Peterbuilt

If you have power on the WHITE going into the TS switch but no power out then maybe you have an OPEN between in and out.
Adaptor gone bad?

0Willcox Corvette

If this helps you, go read how to test the switch at this link Corvette Turn Signal Switch Testing 1967-1968

and this may help.. An easy to read schematic.

0Willcox Corvette

The hazard lamps have their own power source..... the brown wire

With the switch disconnected.. push the brake light switch and see if you have power on white wire at the top.

If you do.. Test for power on the pink wire. You should have power on the pink wire, this is what controls the turn signal flash.

If you don’t have power on the white wire, then go to the brake lamp switch and test for power on the orange wire. The orange wire runs through the brake lamp switch and powers them up.

What happens inside the switch is this:

The tail lamps are fed power from the brown wire in the headlamp switch.
The brake lamps are fed power from the brake lamp switch (orange to switch, then out on white). So power should pass from the stop lamp switch to the turn signal connector. If no signal is turned on then you should have power going in on this white wire and coming out on the green and yellow.

When you use your turn signals, the power for the side you are wishing to turn in is removed by the turn signal switch from the stop lamp switch and placed on the pink wire that is in line with the flasher… thus the flash.

I have another picture for the 69 and new cars that may help you understand the function too.. You can find it in the technical picture section of our web site.

But.. if you only have power on the white wire when you have the switch plugged in, then you have a problem.. Where I don’t know and this is why I advise you to test with the switch disconnected. Test the source wires first.. Orange to white.. and pink.. for power. If you don’t have it there with the switch out of line then trace these wires and find the issue.

And listen to Pete... he's pretty sharp..

Willcox

68 Issues

Pete,

Yeah, that is what I thought too. With the connector unplugged, I verified I was getting power in the white wire just above the connector and at the terminal end of the white wire "inside" the connector. When I plugged the connector together I did not have power in the opposing black/white wire nor could I read it in the white wire above the connector where it was verified prior to plugging it in. Somehow plugging in the connector seems to kill the power in the white wire. This situation is the same when testing either the old TS switch or the new one.

Similarly, with the connector unplugged while getting power on white, I jumped from the white terminal to the green and then yellow wires (same side of connector) and instead of getting brake lights, the white wire goes dead.

I think my next step is to go back and follow the suggestions of Mr. Willcox above. The erratic power in the white wire is very confusing and is making me think the problem is "upstream" of the connector.

Thank you for your input Pete.

0Willcox Corvette

With the connector un-plugged you get power on the white wire... With it plugged in the power drops...
With the connector un-plugged and jumping on the dash main connector to the green or yellow you drop power.

Your issue is probably on the green or yellow wire from the dash main connector to the tail lamps. You should be able to jump power from the white to the green or yellow and get brake lamps.

I think at this point I would possibly start working from the rear and coming forward. Go to the rear lamps and inspect the connections there. Make sure there are no splices or cut wires. Check the sockets and the connectors as well.

If you find nothing suspicious I would pull the kick panel and un-plug the rear harness.... Jumper the white to the green and yellow and see if you get power on these same wires at the rear harness connector. After doing this, if you have power at the yellow and green wires on the forward to rear connector, then the issue is on the rear harness. If you have power on the green/yellow wires then the issue is in the dash main.

Willcox

68 Issues

Willcox,

When I jump a hot wire to either the green or yellow wire at the TS connector, I get brake lights. Based on this I am assuming the problem is not between the connector and the brake lights. Also, I have a new TS switch plugged in and nothing changed.

I just came in from working on/cussing at it again. The power drop on the white wire remains. However, this time I unplugged the brake light switch and jumped the orange and white wires, bypassing the switch.....the brake lights came on. Now I guess the 8 month old switch is dead enough to not work the lights but alive enough to pass voltage on down the white wire to get a reading. Or, maybe as adjusted, it just is not opening all the way.

Do you have the 68 brake light switch in-stock? If so, I may be ordering one later today if I can get the old one out. From crawling up under the dash this looks like it is going to be a lot of fun. I can't even see the two bolts that hold the switch in place!

0Willcox Corvette

Okay.. so without the switch, the lamps work... with the switch they fail. You said you purchased a switch locally but this switch has been discontinued a long time from GM and there were two reproductions of it.. one worked, one was a piece of *&^%. I wasn't aware there was still one available that utilized the jumper style harness connection.

What part number switch and from where did you get it.

Are you sure the wires are correct?

I know, I know.. you had the same issue with the switch that was in the column so I'm just looking for a cause.

You can bypass the brake light switch to see if it's the problem too.. before wasting money on a new one. I'll check back later..

68 Issues

This morning I disconnected the brake light switch and jumped the orange and white wires.....and got brake lights. I am going to try to pull it this afternoon if I can get it out. I'm too tall and too old for working under the dash. Not to mention that my bifocals don't work under there either.

I will look up the part number later. All I remember is that it is ACDelco. With the adapter it plugged right in.

THanks

'75

This is what I suggested in your other thread a few days ago, hope you can return the sig switch and get the wasted time back.

68 Issues

75,

Point taken. I took a short cut by starting with the white at the connector and paid the price of confusion. The power on the white wire made me think the brake switch was working and led in what appears to be the wrong direction.

Got the brake light switch out and it appears that it working. At this point I am guessing all of this was just an adjustment issue. The switch was opening just enough to show voltage on the white but not enough to fully activate it. Putting the switch back in is proving to be a royal PITA. The wasted time and cost of the switch although frustrating are nothing compared to putting the BL switch back in.Trying to hold the switch and bolt with one hand, line up the holes with the other, pressing the brake pedal down with my face, and wiping the sweat (South Florida is sorta warm/humid this time of year) from my eyes with my other hand...and doing all of that upside down!

GDaina

The assembly does have a ground, has a clip and is grounded on the steering column. If the ground is not attached to the column, turn signals will not operate...

Peterbuilt

I'm willing to learn, can you show me where it grounds?

68 Issues

Willcox, the replacement turn signal switch was ACDelco Part #D6211...GM Part #1893592. I don't know if it will actually fit on the column but it plugged in and operated with no problems when using the adapter. I hope this one is not the piece of *&^% switch that you referenced.

0Willcox Corvette

Okay.. so with it by-passed and the turn signal switch connected you have lamps...

I have no way to check to see if we have this on the shelf today.. I know we did last week, but a ton happens in a week around here. I do have the NOS originals but the replacement one will work just fine.

The switch and bracket are no longer made as one part though.. I found that out last week.

And.... just to clear up the air, the turn signal switches do not have a ground. The horn ground wire pass's through the switch but nothing on the switch for grounding circuits.

Willcox

0Willcox Corvette

That switch will work fine.. it's the old delco replacement...

1Fordman

Got the brake light switch out and it appears that it working. At this point I am guessing all of this was just an adjustment issue. The switch was opening just enough to show voltage on the white but not enough to fully activate it. Putting the switch back in is proving to be a royal PITA. The wasted time and cost of the switch although frustrating are nothing compared to putting the BL switch back in.Trying to hold the switch and bolt with one hand, line up the holes with the other, pressing the brake pedal down with my face, and wiping the sweat (South Florida is sorta warm/humid this time of year) from my eyes with my other hand...and doing all of that upside down! [/QUOTE]

For what it's worth, my NOS Delco 68 only stop light switch went south after 4 years. I know your frustration as it's darn near impossible to get the switch back in place with the dash panel in place.

I bought a 69 plunger style switch, got a 3" L bracket from the hardware store and made a bracket to mount the switch. One of the steering column mounting bolts is directly inline with the brake pedal, thats where the bracket bolted to. Works great and if it goes bad, the access is good and 10.00 for a switch instead of a 100.00 + for an NOS switch is even better. Don't bother with the 55.00 switches some of the vendors sell, they're offshore junk. One of my friends with a 68 went through 2 of them in a short period of time. You'll definitely learn new words putting your switch back in place!