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My preference and that of many owners of 55/56 Packards that I know is for the Pacific Northwest hydraulic kit. Installation is even easier than a mechanical switch and the service life of the NAPA SL-134 hydraulic switch has not been shown to be compromised by silicone brake fluid if that should be your choice of brake fluid.

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Owen, thanks for this! I was concerned about the brake fluid issues.

Does the kit come with good instructions? Can this be done from above with the battery out, or do I need to get under the car?

Yes, instructions are included and it's beyond simple. Yes, most easily done by removing the battery.

Brilliant, thanks!

Ok so I received the switch, the original 3 terminal switch was still on there so I thought I was on the right track...maybe I still am.

I installed the switch - which in and of itself took maybe 10 minutes. Getting to the blasted thing however made me look at my 1993 Benz 300D in admiration for how easy it is to access things.

No matter, got it in and also fixed my heater blower as a side job. But now my brake lights won't go off. I seem to remember someone else having this issue on the forum. I'll have to search.

I put some weight on the back of the car, he raised up. Brake lights still on. Wouldn't come back down though. Drove around a little bit thinking maybe that would help. It didn't. Light stayed on and tail stayed up.

Parked him and disconnected the battery until I can figure out what I did wrong.

I have not seen that kit or a schematic of that particular switch conversion to know exactly how it is wired. Assuming the power is going to one terminal of the switch and the other switch terminal only operates the relay, a couple of general possibilities is the wires to the TL and the brake lights got mixed up or it could be the relay is not grounded so is not coming in to switch the voltage between the TL and brake light.

If that is all good the other possibility is the brake pedal is not moving all the way back when released to open the compensator valve in the BTV and allow fluid from the master to bleed back into the reservoir. In that case heat and expansion of the trapped fluid can cause the switch to activate just as if the brakes were applied. You an eliminate that as a possibility by removing one wire from the switch to break the circuit and see if the lights go out.

Thanks, Howard I'll check that out.

After some reading on the forum I'll also try bleeding the brakes and potentially obtaining another brake light switch.

Question: Is there a new parts x-ref on the brake light switch? Everything I've found, which references a Napa part, is not showing as available.

The switch in the kit is NAPA SL-134. The supply of NOS or NORS 3-prong switches is almost nil, hence why folks are going to alternatives like the PNR kit.

Ah, thanks Owen. I must have messed up a number. There it is plain as day.

You might try Echlin ECH SL159 which is available at most Napa stores and fits mid-70s Volkswagens. Same appearance and functionality as the Packard switch but with flat rather than round connectors. I've not tried it myself but I understand that its functionality is identical. If you're rewiring, the appropriate connectors can be used on the harness but otherwise it should be easy to fabricate an adapter. Being of modern manufacture, it should also be able to handle synthetic fluids.