For the life of me I cannot figure this out, so I am hoping someone can help...

On my '65 Dynamic 88, the brake lights do not come on. I have replaced the brake light switch at the pedal, and have power on both sides when the pedal is depressed.

I have pullled the rear seat, and disconnected the connector between the ribbon cable and the rear harness (that sends the power on to the tail/stop lights, back up lights, fuel sending unit, etc.). Slapped a volt meter on the yellow and green wires (#3 and #4 from the right side), and I have power there when the pedal is depressed.

I ran a jumper straight from the terminal with the harness still disconnected and pushed it down inside the connector at the light, thinking I may have a broken wire in the harness, and still no illumination.

Am I correct that the socket for the bulb in the tail light housing provides the ground, and the two leads coming in are for tail/brake lights? These are 1157A bulbs, and I think that is correct but want to confirm. Also, am I correct in that the turn signals are teh same filament as the brake light, and the tail light is the other filament? Since I haven't had brake lights yet I can't confirm.

If that is the case, what the heck am I missing? The tail lights work, the signal lights work, just no brake lights. I have double checked the chassis manual, but all that is there is the main wiring diagram.

Can anyone provide any leads on what to check next? I would certainly appreciate all comments or thoughts.

Thanks,

Steve

 

Edit - I just got done reading the thread above or below this one about the brake lights, too, and wanted to note that I replaced the turn signal switch with one from Rock Auto. It appeared to be the original switch that was in it when I replaced it, and the brake lights didn't work then either.

If I have to pull the wheel again to get at the turn signal switch, what do I look for to see if it is working properly? The only thing that confuses me about that is the fact that I have 12.5V to the body connector when teh pedal is depressed. Darn it.

Thanks,

Steve

 

Have you consulted a priest?

This sounds more like a case of demonic possession.

To answer your questions:

• The socket should be grounded, and the two wires into it are positive connections to each of the two filaments.
• The turn signals and the brake lights use the same filaments, the tail lights use the other filaments. The brake / signal filaments are brighter, the tail filaments are dimmer. And, just to throw you off, the larger filament, farther away from the base, is the dim one, the smaller one closer to the base is the bright one.

If, as you say, the tail and signal lights work properly, and the proper wires are hot when you step on the brake pedal, then you need to find a very young priest and a very old priest.

However, if, as I suspect, your description is not entirely accurate, then we may be able to fix it.
First, you need to check for certain whether power is getting right to the correct bulb terminals when it should. Remove the bulbs, ascertain which of the terminals is which by following the wires, then block the brake pedal down and check the voltage between each light socket terminal and ground. If you don't have good voltage, then that's where you've got to look.

Second, once you know your positive connections to the sockets are good, you need to make sure each is properly grounded. Each one should show zero Ω from the socket to a proper ground point, such as the ground tie-in in the back of the trunk, by the latch.

Third, you need to be sure that the terminals in the sockets and on the bulbs are in good shape, are not wobbling around, and are shiny and free of corrosion, and that the bulbs are installed correctly (the pins sit at different levels, and they should only lock in one way).

I am betting some combination of bad grounds and mislocated bulbs is to blame here, but I can get you the number of the Archdiocese if need be.

- Eric

 

Check the lamp sockets, they loose their spring action on the bulb contacts and no longer make connection. Easy fix is to add some solder to the 2 contacts on the bottom of the bulb....first check for power to lamp socket.

 

I agree. I have not consulted a priest, since I am Baptist. I thought about praying over it and giving it some fried chicken, but I haven't went that far yet either.

The tail lights and signal lights do indeed work properly, but I have not verified that the proper wires are hot when I step on the brake pedal - only that the end of the ribbon connector is hot. I will check the voltage at the end of the socket this evening and report back.

There are ground wires running from the tail light housing mounting stud to the trunk mount bracket that appear to be good, but I will Ohm them from the light socket to the ground point this evening as well just to make sure.

Thanks for both replies so far - I'll be back!

Steve

 

I have checked the resistance from the socket to the ground on both sides, and have less than 1 ohm, which I consider OK.

11.57 volts to the tail light prongs when the lights are on.

2.54 volts to the brake light prong, when the tail lights are ON but the brake pedal is NOT depressed. No noticeable difference in voltage when the brake pedal IS depressed.

.004 volts to the brake light prong when the lights are OFF and the brake pedal IS depressed.

Now for the weird part - Lights OFF, right signal light ON, brake pedal not depressed, left brake light voltage is .02 volts. Not a huge amount of voltage, but still not what I expected.

I may need the number to that Archdiocese.

What else can I check? Obviously there is no voltage to the brake light. At the end of the front to rear ribbon connector (as I mentioned earlier), I have ~ 12 volts when the pedal is depressed (to both connector three and four from the right, the two before the fuel tank sending unit, yellow and dark green). The signal lights and the tail lights work correctly.

I am very stumped, but will gladly get voltage readings on anything that anyone suggests. My gut tells me it's not the sockets, as the signals would not be working if that were the case. But I will *try* to remain open to any ideas (my wife says I am hard headed, fair warning).

Steve

 

I put everything back together tonight as far as the sockets in the light assemblies, connected the wiring harness to the lights back to the rear body connector, and made a probe wire to test all voltages - here are the results:

Headlights and tail lights all work, and are showing 11.59 volts on the proper connector (battery may be draining a bit).

Both signal lights work, and show an overload when the come on on the proper connector (it's a digital Fluke meter and can't keep up).

Signal lights off and brake pedal depressed, no voltage on either of the wires that power the signal lights.

So, does this point to the new signal light switch not passing the voltage? The brake light switch is new and I have confirmed that I have voltage to both sides when teh pedal is depressed. The new signal light assembly came from Rock Auto, and appears to be exactly as the old deteriorated one. As a note, the when teh old one was in, the car didn't have brake lights either.

I am still confused about why I had voltage on the raw connector when the pedal was depressed, but I can let that go for now.

Please, any one have any suggestions?

Steve

 

Hmmmmm...

It does sound like it's most likely the signal light switch.
You could always disconnect the harmonica connector on the column, and jump one wire at a time to 12V, and see if the appropriate lights are lit when you do. If so, then you can rule out bad sockets and bad grounds as the culprits, and all that's left is the switch.

- Eric

 

SOLVED! Here is the prognosis and solution:

When I posted that the brake pedal depressed and no voltage, what I did *NOT* check was the supply voltage. In my ignorance, I *assumed* that since I had voltage without the pedal depressed, it must be there when it was, right? WRONG!

Turns out that whenever the pedal was depressed, I was losing the voltage on the protected side of the fuse. I don't know if it was a bad fuse or a bad block, but I replaced the fuse and cleaned the contacts of the fuse holder with 22 sandpaper and denatured alcohol. Popped the fuse back in, connected the battery, and VIOLA! Brake Lights!

Moral - never assume anything. Always start at the very head and check your voltages all the way through the circuit, to find where they are dropping.

Thanks for everyone's help in pointing me in teh right direction. Time to go for a drive, since I don't have to overly worry about someone running up my butt!

Steve

 

Well there you go.

I just ASSumed that when you mentioned the brake light switch, you had checked all those values.

Simple is good!

Great to see you've got it fixed!

- Eric

 

I was almost ready to suggest a virgin sacrifice to the Olds gods, LOL! Glad you got it figured out!