Can a hydraulic brake light switch be mounted anywhere in the brake system? Before or after an adjustable proportioning valve? Before or after residual valves? Does it matter? Recommendations would be welcomed.
I converted my early Bronco to a duel reservoir master and used a tee off the master so I could use the original brake light wires. The original threaded right into the master, like most did. I ran mine off the front brakes, running off the rears may not be enough brake pressure to activate the switch, depending on how your adjustable proportioning valve is set. On my 57 Ford brake conversion I went with a regular electrical switch off the brake pedal.
It could matter where you put it, it may come on a nano second sooner closer to the master and before any residual pressure valves, which may keep it on if installed after.
The front brake circuit sees pressure first, if in the rear circuit it might take a fair amount of pressure to trigger it.
Much better to install a quality mechanical switch that works off the brake pedal vs messing with a hydraulic.
I’ve got a hydraulic switch that came mounted in my adjustable proportioning valve. As far as the guys saying be sure you can get at it to change it, I have a friend who has been running the same hydraulic brake light switch on his roadster for over 20 years now and never had a failure.
I've seen enough trouble with hydraulic brake light switches that any car I have that uses one also has an indicator light inside the car so I can see if it's working. No question, put it somewhere easy to replace because you're likely to have to. I'd put it in the front brake system.
I'm with V8 Bob, I was just out in my shop adjusting the mechanical switch in my roadster, they are cheap and easy to install, mine is from a 77 international scout, cost a whole twelve bucks from cole-hersey.
If you can buy a brand new 20 year old hydraulic switch, then you won't have any trouble with it. But if you buy a new brand new switch, it'll probably die soon. So yeah, put it where it's easy to install and wire and work on and gets full MC pressure. But still you want a 20 year old NOS mechanical switch, instead, if you can find one that fits.
My truck has a hydraulic switch which has worked fine for several years. Not sure if it was an NOS unit? Now that I've installed a two circuit master cylinder, I was mostly wondering if it would perform differently if it were placed behind the adjustable proportioning valve? Less pressure there right? Seems logical to place it in the front circuit or before the prop. valve if placing in the rear circuit? Well, I'm here because my "logic" does not always seem to apply when it comes to brake systems.
I used a Ron Francis low pressure switch in my rear line (drum-drum), has worked well since 2011. Not pictured is my drive shaft safety hoop.
I had a hydraulic switch on my 48 for 15 years and not again. Longevity may depend on how exposed to road debris and water though. I felt that had something to do with mine failing every year or so. To the point I kept a spare in the truck but I was driving the truck every day as my daily driver and it wasn't a garage queen that averaged 50 miles a week over the year. When I worked in shops in the 70's I replace far more Ford Pressure brake switches than I replaced mechanical of all kinds.
Mine is on the distribution block. The switch it came with leaked right away. The NAPA replacement took too much pressure for it to trip. Found a low pressure one on Ebay. Also carry a spare. The replacements years back were a lot better.
I have heard that the short life of hyd switches can be from using silicone brake fluid. I like the cleaner appearanc & no moving parts with hyd switches. Greg
When I built the truck in my avatar I used a low pressure brake light switch. It lasted 5 years then last summer I noticed it took a lot of pedal pressure to bring on brake lights. Not wanting to break into the system I left the pressure switch in place and wired the brake lights through a mechanical switch activated by the brake pedal. The brake lights now come on with just a touch of the brake pedal and the switch can be easily serviced.
I was under the impression that the OEM proportioning valves on a ford let the rears take first to stop the auto tranny from continueing to spin the wheels, pushing the rearend and maybe causing a spin... it does this for just a few seconds then about 70% ? goes to the fronts where most of the stopping power is... for the northeners…. have you had bad rear brakes in an automatic and tried to slow to a stop on glare ice, had the rear wheels go on spinning and have the arse end try to pass you... ?
Here's some pictures of how I would like to plumb. Not much room on this old Mopar and being a retro rod, I try to minimize altering things too much. Anyhow, it's the easiest way I could come up with and not have to mess with any wiring changes. My initial query was concerning pressure switch placement. I'm hoping it's OK to put the hydraulic pressure switch behind the prop. valve? I'm now thinking it should not matter where the hydraulic pressure switch goes due to it must have some minimum amount of pressure to activate? I'm just mocking it up now and will fabricate a mounting bracket for the prop. valve. The front port on this master cylinder will feed to the 10psi residual in the photo. Rear port will go to new front discs via a 2psi residual. See any mistakes?
That will work fine, mine is just like that. I installed the proportioning valve vertical and have it come up through floor at front edge of seat..
My Wilwood MC came with one. I didn't use because of the electrical connections. Put the original on.
Easiest ? Should safety not be the priority here ? Have you not read the other posts above. With all due respect, you ask advice and seem to continue to ignore it. Posts 2, 3,4,5. answer your questions. Post 6 is from one of the most experienced brake guys on here ! Many other posts have exceptionally good advice. Post 14 doesn’t explain his system, so may be completely different to your setup. There are plenty of other threads on this topic. Some people have had success with hydraulic switches that on other threads are referred to as HD, I assume over there, maybe refers to Harley Davidson, I am not sure. And there seems to be a right way up to mount them. That’s enough of my one finger typing wasted........ Please Carry on.........
Yes Clem, I have read all the posts and am not ignoring anyone. I don't do this stuff all the time and I have much respect for the knowledge and experience of many of those that love these old vehicles. In fact, V8 Bob especially and several others have given me great advice pertaining to my current front disc brake and split master cylinder project. I consider my truck a resto-rod. Had it for over 40 years. I've made many changes to it including T5 speed transmission, later model posi differential with taller gearing, 12volt conversion, alternator, halogen headlights,and other things. I also have always done everything possible to keep it so I or someone else could easily restore it back to stock. Still have all the original parts. In reference to the pressure switch, I agree that a mechanical switch is overall a more reliable choice. It's a bit difficult to install a mechanical switch and make it look right on this truck due the pedal geometry and how crowded it is in there. I would have to mess with the wiring harness as well. So, perhaps I'm lazy, but it was an easy choice to put back the hydraulic switch which has worked perfect for me for many years and plugged right in looking like it came from the factory. I have NOS ones on the shelf as well. So, It's just a choice I made. I just finished bending up the hydraulic lines. I would appreciate any constructive criticism if anyone sees something I've missed. Photos below:
Appreciate your reply. When I pulled my hydraulic switch and went mechanical, I just extended the wires a little, but your wiring loom may be different. I am curious though as to the loops in your lines, is that to make bleeding easier or for vibration reasons or something entirely different ?
Yes, for vibration and flexing. The original line from the master cylinder had a loop to the tee on the frame. I figure the Mopar engineers knew what they were doing. The master cylinder is mounted to the bell housing which moves with the engine torque. Even though the motor mounts on my truck are "almost" rigid, there is a a little flex when the engine is revved. Over time I imagine the lines might fatigue and crack?
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