For those of you that still stubbornly cling to using a hydraulic brake lamp switch but have to replace them frequently like me, then you should consider this. In my infinite wisdom as a 20 something building a car for the first time a long time ago, I decided that the best possible location for the switch was in the rear of the car above the rear end instead of near the master cylinder where it would see pressure from the front brake circuit right away. But no, I was sure that having intermittent working brake lamps was the better option, mashing the pedal really hard to get them to work was my go to move. Finally I found the sense to make them work at the touch of the pedal. I used an industrial hydraulic switch made by Suco, it is also adjustable by turning the center screw. Backing the adjuster all of the way out closes the contacts so I set it up by running the screw in until the lamps turn off and then gave it another 3/4 turn. Now I have consistent brake lamps at the slightest pressurization of the brake system and the best part is that this switch is ROBUST, it will not see over pressure until it hits 8700 psi and will not burst until in excess of 10,153 psi. Adjustable switch activation pressure range is 1.5 psi - 725 psi depending which adjustment range you get, there are several variations. It will handle up to 42 Volts. Now the rub, they run about $80.00 depending where you source them, there are knock offs online but I doubt the cheapy ones can match the specs I listed. Sounds high, but these switches are meant to work for years in environments much harsher than a 91 year old cars brake system. Enjoy.
I like the way you think. I replaced the same on the hydraulic system of a bucket truck that increases the rpm when pressure is applied. Never thought of it for this application. Thanks for sharing.
Well hydraulic fluid is a very spicy fluid, can't imagine DOT3 brake fluid being much worse. I actually have DOT5 in my system so my results could potentially be different than others. Here's the specs directly from Suco. Edit: looks like you would have to select the material at time of ordering, which in this case is EPDM for brake fluid compatibility, I have no clue what's in mine. I will be keeping an eye on it. Looks like my great idea was only half baked. https://suco-tech.com/product/0163/
The part number is figured out from the table on the company website (https://suco-tech.com/product/0163/) I posted a few comments up, I potentially have the wrong one. If read it correctly it would be 0163–41504–2–060, with the "2" designating it as having the EPDM seal that brake fluid won't attack. Amp rating is 4A at 42V, which would be like 168 watts approximately, which can handle the 27 watts per bulb of a standard 1156 0r 1157 bulb. There are many configurations on the website in regards to pipe thread size and terminal style, etc.
I had a NAPA one, I really had to stand on the pedal to make the lights come on. I found one that trips at 25 psi on eBay, also bought a spare. I like to keep it simple and easy to access.
That's not how the rating works.... The amp rating is for the contacts and is independent of the voltage rating, 4 amps maximum in this case. The voltage rating is for arc suppression capability while switching. That's why the ratings are given separately and watts aren't mentioned. The typical 1157 draws 2.25 amps each, you're exceeding the switch rating by .5 amp if having two brake lights. But note that current amount is once they're on. Those have an inrush current of almost 5 amps each, so each time the switch operates you're putting 9+ amps across those contacts, exceeding the factory switch rating by about 130%. Now that's a pretty heavy-duty switch, it may be able to withstand the overload for a considerable time but this will shorten the switch life, just how much will be hard to say.
Is it made to work well with Silicone DOT 5 brake fluid? Some switches fail after a year or two with silicone brake fluid.
Pocket Nick: Please let us know part # of SUCO switch you used. Thanks. Here's a listing. https://suco-tech.com/products/pressure-monitoring/mechanical-pressure-switches/
The counterfeit Chinese switches are well documented. If they do not last 20 years, they're junk. The Harley switches are the way to go.
Member 100% Matt sells a brake switch that has the brake fluid separated from the switch so switch can be replaced if needed without opening up the fluid circuit. You can contact him for more info. He is in CT and sells them through Millworks in MA.
I've replaced a lot of the OEM type over the years. That's why my current project will have a mechanical, arm to pedal actuated switch. As soon as the pedal move enough for the push rod to hit the master piston, it closes. Lots of choices from various cars/trucks. Of course I have suspended pedals so it is easier than frame mounts.
I don't really trust anyone to ever hack into my brake lines...... especially me. I sleep better at night with a mechanical triggered electric switch.
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