Packard Forum Index » Pre-War (1899-1942)

At this point, the next step is as others have stated. Do you have a voltmeter? If so, remove the jumper you installed. Then, you need to measure the voltage from one terminal of the brake lights switch to ground. If it is at 6V, then that is your “hot” to the switch. If you don’t have 6V, then measure the voltage from the other terminal of the switch to ground. Again, if it is 6V, then it is your “hot” terminal.

At this point, only one terminal should measure 6V, but one terminal should read 6V. If you don’t have 6V at either terminal, then you have a wiring problem prior to switch.

If one terminal does have 6V, and we know that the switch is not the problem, then you have a wiring problem after the switch.

Once you determine if the problem is before or after the switch, we can start the next steps of the troubleshooting.

No need to remove the jumper for that measurement. There is either power or there isn't so whether the jumper is connected (both terminals should have power) or it's not (one terminal will have power) the test is the same.

Agreed, I just recommended to do that to follow best practices in trouble shooting. That is to work with as few “changes” as possible at one time. The first step was the jumper to see if the problem was the switch. That let us conclude that the switch is not the problem. Best practices is to then return the system back to baseline, Then, take the next step.

Quote:

I went back and reviewed this entire thread... In your first post, you mentioned that your rear turn signals work, but not the brake lights. Based the quote above, your rear turn signals and your brake lights use the same bulbs AND the same wires from the turn signal controller to the brake lights.

So, here are the most likely causes of the problem:

1) You are not getting power to the brake light switch. Normally, one terminal of the brake light switch would have power all the time. Then, when you press the brake pedal, the contact in the switch closes, sending power to the turn signal controller. The controller then passes that signal on to the brake lights. As I mentioned in my previous post, check to see if you have 6V at either terminal on the brake light switch. If not, that is your problem. I you do have 6V, go on to Number 2.

2) You have a disconnect in the wiring between the brake light switch and the turn signal controller. That is, the controller is not getting the signal when the brake light switch contact closes. With the jumper installed on the brake light switch, check to make sure you are getting 6V at the point where the wire from the brake light switch connects to the controller. If you do not have 6V there, then the problem is the wiring between the switch and controller. If you do have 6V, go on to Number 3.

3) If the signal is getting through the brake light switch and to the controller, then the controller has likely failed.

Don B has given excellent information. If you verify you have 6v power from one of the auxiliary fuses on the headlight switch that is getting to the brake light switch then with the jumper bypassing that switch, the power would be present on part of the brake light wire so it must be getting interrupted somewhere between the brake light switch and the turn signal switch or in the switch itself. Because the rear bulbs are shared, since the turn signals have a different power source and they work, we know the wiring between the turn signal switch and rear bulbs would be OK.

The turn signal switch will have some kind of structure to support and hold its contacts in position much like the brown fiber support shown in this photo of a Packard switch. There will probably be 6 wires going to the switch board and depending on the type and where the flasher can is located, there will probably be 7 to 9 wires in the black cable between wherever the connections to the car wires are being made and the switch assy on the steering column.




If the brake light wire is not broken or disconnected somewhere before reaching the switch then the other likely problem is the brown fiber or phenolic support board holding the wire terminals and contacts has warped letting a contact or two drop out of position so the wiper cannot connect or else the contacts themselves are burned or very dirty. The wiper moves when the lever is moved and connects the 4 contacts going to the light bulbs in various combinations to the wires coming from the flasher or brake light switch. Some bulbs flash, some will be off and another can be on solid depending on what is needed. Both dirty contacts and warped boards have been issues on Packard switches and your aftermarket switch would likely also be susceptible to the same issues.

Again, if you can find a brand or model number of your controller assembly there might be a wire diagram available online. May not be as detailed on the internal switch construction like the photo showing details of the Packard switch but at least the external wire colors and function information should be available.