Guess I spoke to soon, while I was inside, my wife happened to notice the brake lights were on again. So, with the adjusting rod just about backed all the way out I'm gonna say its the switch, the brake switch is the only thing that controls the brake lights.

 

Since you are considering replacing the switch again, I'm going to suggest that you take care with the brake switch. I am of the opinion that many of the gripes of their reliability stem from improper installation where too much gorilla power was used along with an adjustable wrench (causing deformation of the unit) instead of a a more gentle consistent approach with a deep 6 point socket. There is no need to go all Hulk Hogan on it or anything.

The 91A-2077 is a banjo bolt. The clocking of the hole doesn't matter; the manifold block has a larger diameter so the brake fluid will flow out of the hole in the bolt and around the shoulder and into the holes in the manifold block. What is very important is cleanliness and paying attention to details. Examine the sealing faces of the block. They must be clean and ribs well defined: https://www.dennis-carpenter.com/tru...r-outlet-block


The flange of the banjo bolt must be clean, flat, and clear of all debris. If you have any doubts on being able sufficiently clean and revive your existing, both the banjo bolt and manifold block are available new. Also, you should use new copper washers every time as they deform into the ridges to make the seal. While the two copper washers may initially look the same, there are actually two different copper washers specified. 91A-2151 goes between the bolt and manifold block. 91A-2152 goes between the manifold block and master cylinder. They both have a .81" outer diameter, but .61 and .51 inside diameter respectively.

Again, when installing the brake switch, go easy on it and use a 6 point deep socket. Remember, the threaded portion is small, soft, and has a hole. It is very easy to damage the unit and the internals with excessive forces.

 

Thanks for the information, very informative, I suppose I could have damaged the switch, its been a while since I installed it. I actually replaced the master cylinder some time ago because of the same problem. Once I replaced the master cylinder the problem went away until now. I reused the switch so it is possible the switch was damaged. Its funny though, if I disconnect the battery the brakes lights will go out, a while later if I reconnect the battery the lights do not come on until some time has gone by. I'm thinking of calling my truck "Christine". I'm to old and have vertigo, crawling under this truck causes issues. I'm gonna put a mechanical switch on the pedal and be done with it. I do appreciate your time and knowledge, thank you.

 

I am nut sure why it is so hard to make a good pressure switch. I have 6, 50's era Ford cars that used them. I Thought I had found the problem by buying Hella brand switches. They are not sold in the US so I paid a premium to order them from Australia. No luck there, after 6 months, it failed. The problem is that the switch will either not work at all or the brake lights will stay on anywhere from 5 minutes to an hour. I am not sure why this is such a hard switch to get right. The OE switch would last for years. I would pay a premium just to get good switches.

 

I read somewhere, hell, may have dreamed it, but you are not supposed to use synthetic brake fluid with these switches. I replaced my entire system and still only used regular fluid. Because I went with an upgrade dual bowl master cylinder with proportional brake valve I changed to mechanical brake switch.

 

I've used synthetic for thirty years in my 51 and only replaced the brake light switch one time and I bought one from auto zone and it's still working.That was probably 10 years ago.

 

A little late so I may have to look in the shop in the morning, but what I found on the internet, and previous posts here, is that the NAPA SL134 pressure switch is not compatible with synthetic brake fluid. There is a flyer in the box, “apparently” the synthetic can clump debris and stop the switch from functioning. A lot of people state they have never had any issues using synthetic and that is great. Not a huge difference in price but since I still use drums for rear brakes I will play safe.

 

I still have front and rear drums and I know some don't like it I still have original style master cylinder but i did run all new stainless brake lines 30 years ago.

 

I am using DOT 4 brake fluid. I understand the problem with DOT 5 as it is more viscous and may not activate the switch. I know that my problems are not the fluid. I do not know when they quit making these things in the US, but the Chinese ones are horrible.

 

I wonder what the brake line pressure factory VS a converted power brake system such as a Mustang 2 master cylinder. I’m plumbing in my pressure switch for now during my conversation. After seeing this switch and a bit of research, the mechanical switch here is the switch style recommended by No Limit engineering when converting to power brakes. It looks fairly simple to hook up.

 

@Christopher2 , our larger trucks had factory power brake options with the C447 that operate in similar ranges to the stock power brake options on the Mustang II (Note in my signature that I actually have both!).

 

I have the no limit set up. You have to plump in pressure residual valves front and rear which they don't tell you which adds a lot of connections.

@Christopher2 I used the simple firewall mounted mechanical lever switch and wouldn't do it any other way. It works flawlessly, easy to set up and if by chance it breaks it's is a 10 min swap. No brake bleeding fluid running everywhere etc.

There are quite few tricks to getting that brake set up right. It's a great kit but has some quirks as the all do. Happy to share more if you want to DM me and have questions.

I JUST REALIZED I started this thread LOL. I mounted mine like it is shown in post #6. I will take a picture later of mine installed since I never updated this thread. I used the straight lever version from Summit I believe.

 

If you are getting good service out of the pressure switches, I think you are extremely lucky. I respectfully disagree with you. I have 7 Mid 50's Ford vehicles with that switch. The original switches were near bullet proof. They worked flawlessly for years, I am lucky to get a year out of the replacements. I even bought some Hella brand switches from Australia, in hopes of better results and it is garbage also. I found that al the ones I can find are made in China and are of questionable quality. The brake lights will stay on for 10-15 minutes with no pressure on the pedal. I maintain my cars to high standards, replacing the cracked and broken wires with OE style harnesses. I also have clean clear fluid in the system. The problem is not wiring, master cylinders, but the horrible quality switches made in China.

 

If the argument is China=bad, then the same argument should be valid any part made there, including other style mechanical switches. The SMP/Echlin options I listed come from entities with a strong North American presence with manufacturing facilities including locations in Greenville, South Carolina, Independence, Kansas, Milwaukee, Wisconsin, Mishawaka, Indiana, Reynosa, Mexico, St. Thomas, Ontario and other locations. This was confirmed by looking at current NAPA/Echlin SL134 packaging. Don't like this brand or country of manufacture - I provided a list of alternative manufacturer part numbers across various threads here so take your pick.

These style pressure brake switches are not an obscure or obsolete style component - they are still used in current designs including industrial equipment such as aircraft tugs, motor cycles, motor sports and so on and so on. They are/were also used in relation to various military weapon support systems for the following: F-14 Tomcat, S-3B Viking, E-2C Hawkeye, H-3 Sea King , H-46 Sea Knight, CH-53 D/E, RH-53, F/A-18 Hornet, SH-60B, AH-1J Cobra, UH-1N, TA-4J, AV-8B Harrier, C-130F Hercules, KC-130 Hercules, P-3 Orion, F-5, C-2A, H1, MH-53E, AH-1W, SH-60F, HH-60H, HH-60J, H-60, FA-18 A-G, LPD-17 Class Amphibious Transport Dock, MB-4 Aircraft Towing Tractor, Landing Craft Air Cushion, Nimitz Class CVN, Wasp Class LHD, Tarawa Class LHS, Whidbey Island Class LSD, FMS - Newport Class LST

The broader reality is that these pressure switches have remained in continuous production and use for decades because they can be simple, compact, robust, and well-suited for demanding environments. I am not saying that it is impossible to have supplier defects - it can and does unfortunately happen with any product. There are also many variants of this product with different contact metallurgy, different response pressure ratings. To those that have 4,5,7, or 100 failed pressure switches, could the common contributing factor be something else such as the installer? Even more telling if the factory installed switches are considered "bulletproof" - just maybe the factory installed them correctly?

 

[QUOTE=bmoran correctly?[/QUOTE]


Just my experience, When I changed over my master cylinder it came with a new in line break switch. It malfunctioned right out of the box, the old one (from the 90s) worked fine but I had to jimmy it to the adapter. Tried to get one from NAPA and had a correct thread problem.

At the end of the day it started to look like frankenstein with the different connections and adapters. More connections more possibilities of issues. So went with the pedal switch and have had not issues. I can change it under the hood, less connections, less jacking the truck up to get under it, etc...