T/L Brake light switch

Posted by Dave Brownell On 2017/3/19 14:22:21

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.