‘67/‘68 vacume parking brake & backup light switch

[MERNJ]

Looking for a NOS mopar part # 2857486 vacume parking brake/backup light switch used in the ‘67 and ‘68 Inperials. Switches were known for failure. Hoping maybe someone has a nos or good used switch. See pic below.
Thank you, Mike

 

[detmatt]

I have successfully repaired a few non working units but the other thing that commonly happens is the pin in the column that moves the lever falls off so check that too.

 

[SPF Required]

What @detmatt said. The switch itself can usually be rehabbed, but that little pin is probably missing from the lower end of the column. I have tried replicating the pin, but no luck yet.

 

[MERNJ]

What @detmatt said. The switch itself can usually be rehabbed, but that little pin is probably missing from the lower end of the column. I have tried replicating the pin, but no luck yet.

utilizing a mirror we can see that the sliding pin in the column goes from the fully open position to the closed position in drive. I purchased a rehabbed unit from Dematt, I believe, but the backup lights won’t work when the vacume hose connected. Disconnect vacuum hose and back lights work. So we have unit connected w/o vacume feed hose. Would rather have back up lights then auto release emergency brakes.

 

[MERNJ]

Thank you both for replies

 

[detmatt]

utilizing a mirror we can see that the sliding pin in the column goes from the fully open position to the closed position in drive. I purchased a rehabbed unit from Dematt, I believe, but the backup lights won’t work when the vacume hose connected. Disconnect vacuum hose and back lights work. So we have unit connected w/o vacume feed hose. Would rather have back up lights then auto release emergency brakes.

I’m trying to make sense of this and I can’t think of why the vacuum side of the switch is having an effect on the reverse lights.

 

[MERNJ]

Agreed, we put a test light on the switch with and with out vacuum, only when the vacuum hose was disconnected did the test light work, we did the same for back up lights and found same results. There is something about the vacuum within the switch that disrupts the electrical connectivity for the back up lights

 

[detmatt]

Agreed, we put a test light on the switch with and with out vacuum, only when the vacuum hose was disconnected did the test light work, we did the same for back up lights and found same results. There is something about the vacuum within the switch that disrupts the electrical connectivity for the back up lights

I have a couple more of these at my shop I’ll have to look into this situation.

 

[MERNJ]

Thank you, would be interested in another if you could solve.

 

[detmatt]

Ok so here is the opening in the tube that rotates with the gear selector that engages the lever on the switch. It’s not a pin at all that is missing here but a piece of plastic with sheet metal spring that I think aids in holding the plastic piece in place. It’s the plastic and sheet metal spring that becomes loose and falls out of the way inside the column thereby no longer moving the lever that both disengages the parking brake and activating the reverse lights. In the third and fourth pictures, you can see the plastic piece and sheet metal spring and on the 3rd pic you can actually see the clean spot where the spring loaded lever makes contact with it. In the 5th pic the plastic piece and sheet metal spring is in place.

 

[MERNJ]

Wow, completely makes sense. My setup is pic #1 and 2. The plastic piece has long fallen by the wayside
The purpose of the plastic insert is to provide a friendly surface/contact point for the moving plastic tab/finger/lever on the switch. As proof of the latter please see my pic below. You will notice the right side of the lever is flat, yours had a bump. Mine is flat from years of contacting the metal sleeve moving back and forth with the gear selected. The sharp metal sleeve wore down the plastic.
We were wondering why Chrysler would have such a ridiculous design. The plastic insert makes sense, too bad the insert itself did not hold up.
Anyway thanks for the good detective work. Still doesn’t explain why I loose connectivity on the back up lights with vacuum hose connected. Maybe it effects position of lever, which is very sensitive.

 

[detmatt]

After spending some time with some switches I have here I still can’t explain why having the vacuum attached for the brake release would have anything to do with the operation of the reverse lights. It’s a relatively simple two in one switch that relies on one action of the gear selector mechanism to trigger them both. So as long as the lever is in tact, along with the parts inside the column that engage it and your switch is good your parking brake release should work without the connector for the reverse lights plugged in and conversely your reverse lights should work even if you don’t have the vacuum connected to the brake release. They are independent of each other.
The disassembled switch in the picture shows the simple internals and yes, the lever is broken off and missing on this one. It is too far gone to save as one of the electrical contacts is burnt also.
I do have an NOS 1 still in its box(NFS), along with an intact original, both of which seem to be in good working order as far as the reverse light switch is concerned when tested with an ohm meter.
i’m not convinced that there is something wrong with the switch that you have there.

 

[MERNJ]

By the way, everything else on the car works perfectly, (even the atc), except clock and auto brake release
Www.1967imperial.com

 

[MERNJ]

I agree that both internal systems should independent of each other. Perhaps the vacuum is moving the metal connector contact that completes the light circuit. It’s an aweful lot of turbulence goin on in that switch?

 

[detmatt]

I agree that both internal systems should independent of each other. Perhaps the vacuum is moving the metal connector contact that completes the light circuit. It’s an aweful lot of turbulence goin on in that switch?

Where is the source of your vacuum?

 

[MERNJ]

It’s set up exactly as the pic you posted indicates. Nobody ever messed with it. Would be difficult for you to duplicate doing a bench test

 

[MERNJ]

It’s set up exactly as the pic you posted indicates. Nobody ever messed with it. Would be difficult for you to duplicate doing a bench

 

[MERNJ]

I think the vacuum is maybe causing the contact bridge or contact points of the switch to move around, preventing continuity

 

[Clover]

We were wondering why Chrysler would have such a ridiculous design.

They bought it from GM. It’s a patented Saginaw system.

 

[detmatt]

D

I think the vacuum is maybe causing the contact bridge or contact points of the switch to move around, preventing continuity

id you ever get anywhere with this?