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As sure as the sun rises, with a show that I really want to drive a Packard to coming up this Saturday, all three Packards have decided to have issues at the same time. I had done my due diligence by replacing my BTV unit last month in the Esquire, and all seemed normal until folks started telling me that the brake lights were staying on. Having had a similar problem several years ago, I replaced the switch with a NOS (still in an unopened S/P package) that came with the car. Problem seemed solved. Until I put in the rebuilt BTV from our favorite supplier, all seemed well until last week when the brake lights started staying on and the T/L stopped compensating because of the circuits.

My first question is how long do these switches tend to last under infrequent or light use? At the current price, I'd rather not order a new one without ruling out something else. Because of its placement, I did not disturb the switch knowingly when I did the BTV work. I did do a bench bleed and bled the system afterwards, and my son wondered if an air bubble left behind might cause the switch to malfunction. I have bled the system twice since, to no avail. The new BTV seems to be working fine brake-wise, but could something be trapping fluid under pressure, causing the switch to close? The wheels turn normally, so I don't see how the system could be trapping fluid.

The brake lights will come on anytime the battery is connected. A spare switch (the old one I removed) also closes the circuit even though it's not connected to the hydraulic system. Connecting either causes the lights to shine. Does the hole in a switch need to be pre-filled with DOT 3 before installing in the fitting, or does normal brake line pressure do that?

Getting to the Palmetto show involves about 60 miles of interstate travel, and I don't want to do it with brake lights blazing. Alternatively, driving the 1950 with overdrive would work except for doing it without the seat belts that have yet to arrive. I hate the thought of showing up in a newer Corvette or VW, but may have to do so until the Packard stars come into alignment. The opportunity comes but once a year, so maybe I'll just have to settle by showing off Packard pictures on an iPhone.

Nothing needs to be done to the switch as to bleeding it. Pressure in place does it all. Old and even NOS switches seem to be hit or miss. One thing is make sure the pedal is retracting all the way so there is no chance the compensator valve is staying closed. If the switch is active, pull back on the brake pedal and see if it goes out. If it does there is something binding the pedal that needs to be found. If no change then a bad switch.

Rather than get another 3 pin switch, I would get one of the replacement kits from Dwight Heinmulller or the Pacific Northwest region or maybe even one of the vendors. That kit uses an ordinary easily found and inexpensive 2 prong switch and adds a relay to do the TL switch function. Original wiring plugs right in.

Several of us have gone one farther and completely replaced the hydraulic switch. We have mounted a mechanical switch to the steering column inside the car which is operated directly by the pedal arm. A short extension loom goes out and connects to the original plug.

These switches are now as much as 60 years old, there might have been a run of service replacements a short while later, so they are all at least 50 years old. Are you running silicone fluid? (Dot 5) that is known to eat the old stock switches in short order.
You can use a brand new regular two-prong switch available from NAPA in conjunction with a simple relay to do what the OE three-prong switch does. All of that is buired under the battery tray, so someone would have to look hard to find it .

I have not experienced early failure of the OEM-type switch in my own car which uses DOT-4 brake fluid, the unit in the car now has been there for 20+ years. But I've frequently heard of early failures when using DOT-5. IMO the simplist and most inexpensive solution when you experience switch failure and don't have an OEM type replacement or are using DOT-5 fluid is to go to the conventional switch and relay system that Mr. Pushbutton has mentioned in his post just above. It's available very inexpensively as a neat little kit as shown below, the hydraulic switch is a NAPA SL-134 (United 7715) or equivalent, and is included in the kit. This is the same switch used in almost all Packards with hydraulic brakes from 1954 and back.

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I did like Howard, I put in a mechanical switch on the steering shaft and had it activate a relay to turn on the brake lights. It's been working for over 16 years and over 60,000 miles. It's on my 55 Clipper.

I had the left front wheel axle nut too tight and it made heat that traveled up and would melt my hydraulic brake switch. After backing off the wheel axle nut, I went ahead and put in the mechanical switch. The load levelers work just fine with the relay and mechanical switch.

The switch is a normally closed switch and the brake pedal rests on it so the switch is off (open) and so is the relay so the load levelers work. When I push on the brake, the brake pedal arm releases the switch (closed switch), so now it turns on, and the relay turns on and turns on my bright brake lights. When I release the brake pedal the switch is compressed and the relay is turned off (and so is the brake lights) and the load levelers can start working.

You can't see the switch and relay because they are under the dashboard.

My 2nd Clipper is working fine so I won't put this change on it, only if I need to.

I tried replacing the brake-light switch normally, but DOT5 ruined it quickly. I replaced it with a standard GM switch that originally lights the brake lights and turns off the cruise control.
I bolted it to the bottom of the steering column and hooked up the cruise portion to the TL controls. I have had this installed in my 400 since the mid-90s and am going to install it in my Caribbean as well.
It costs somewhere around $10.00 and you have to make up your own wiring.

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Assuming it is for a 56 here is a a photo and bracket that would work for the switch Randy shows and probably the one mentioned by duane.g. I used a different switch but all have the same principle. The pedal arm depresses the switch plunger when brakes are relaxed. The bracket is simple to make and holds onto the column with a heat shrink covered hose clamp holding the two bent up tabs to the column.

The 1" dimension between column and switch hole may not work for a 55 because of the different pedal arrangement so that dimension would need to be verified on 55s

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