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brake pressure failure switch

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Woodie

Woodie

Jedi Warrior
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I found a problem, but do not know if it is related to no brakes lights. My pressure failure switch on the passenger side of the engine bay has two wires to plug into it. Both wires are disconnected and have no terminals to plug into the connector. I think the part I want is vicy bit 7-434, but cannot find a Moss equivelant. Anybody know? In the mean time can these two wires be jumped or left disconnected for the system to work properly (without pressure failure warning). ANd will this affect my lack of brake lights..(still planning on getting to the brake switch later today.)
 
Are you talking about the brake pressure differential warning switch? (Kind of an "H" shaped doohickey with lots of brake tubing and wires coming off of it). If so, jumpering the wires together should turn on a dash mounted warning light but shouldn't affect the brake lights on the back of the car. I think these are NLA or very expensive if you decide to replace them as an assembly.
 
Ahhh, or is that the pressure switch the turns on the brake lights. If so that would be a big clue as to why they don't work. LOL
 
Doug, yes it is the doohicky (love that word) on the inside of the passenger side fender. It is the plastic plug/switch that screws into the "H". There is a plug that mates to this plastic switch/thing. The wires have been pulled out of the plug part and there are no SMALL pins on them to fit into the plug. I sourced the past at Vicy brit for $50 odd dollars, but do not know if it comes with the plug part (part of the harness??) or just the part that screws into the hydraulics "H" ..
 
Jack I think the pressure switch to turn the lights on is in the brake box on the other side of the engine. I am going to check that is hooked up and functioning in about 3 or 4 hrs. I will disconnect and jump the two wires, and see if I have brake lights..if I do great ...If I don't hmmm then what???
 
You may be very correct Woodie, if it was on a Bugeye it would the the brake pressure switch. Could they do that, yep bet they could. What does it do? Let us know.
 
Woody,

Be careful and make sure you know what you have. A 1970 midget, US spec, should have the dual-line master cylinder and the "BRAKE" light on the dash right in the center. If so, that H-shaped doohickey should look like this: https://home.comcast.net/~kvcbk/PDWA.jpg

As was mentioned earlier, all this switch does is indicate a leak in one of the two lines of the brake circuit (front or rear) and turn on the light in the dash. In my car, the switch is disconnected, since I'll know if there's a brake failure or not! /ubbthreads/images/graemlins/grin.gif The switch that actuates the brake lights should be screwed in to the end of the pedal box right by the brake pedal.

IMPORTANT: (and don't kill me if I'm telling you the obvious) /ubbthreads/images/graemlins/devilgrin.gif You need to have the ignition on in order for the brake lights to work. MGs are weird this way, and it'll drive you nuts trying to find the problem. BTDT!

Hope this helps!
 
Thankyou CK, again I learned something. Amazing thost Brits. I always figured if I steped on the brakes and kept going I would know there was a problem. Sigh another item legislated by the safety folks I supose.
 
CK THAT's it !! See the white plastic screw in switch, my wires that go into that are bare, no little plugs on em. The wires are not twisted together, (no lights on the dash) I guess I leave them that way, cause to connect them would light up my dash light right in the center of the dash.

HMM key on for brake light...live and learn, live and learn
 
[ QUOTE ]

IMPORTANT: (and don't kill me if I'm telling you the obvious) /ubbthreads/images/graemlins/devilgrin.gif You need to have the ignition on in order for the brake lights to work. MGs are weird this way, and it'll drive you nuts trying to find the problem. BTDT!


[/ QUOTE ]

This makes sense, (at least on a '77 midget like mine) since power to the brake light switch is provided through the power side of the windshield washer pump. The windshield washer pump would be on the switched power side of the fuse block.
 
Yes, you can leave them that way, better yet, just put some electrical tape on the ends so you don't accidentally short them on something. You can leave the switch in the housing, it won't harm anything. Some people put a bolt in its place to keep the shuttle from moving. Not a bad idea, as bleeding the brakes can cause the shuttle to move, and if the swotch is in place, the pin in the center of the switch will keep the shuttle from returning to center. I usually remove the switch when bleeding, as the shuttle will re-center itself then.
 
I like the idea of locking the shuttle. That makes good sense. There was a link (now gone) on the Buckeye Triumph web site that discussed how to make new shuttles for these valves and what seals to use with them. I think they took the link down for liability reasons.

I should have mentioned (regarding the brake light switch) that the early Minis like mine have a reputation for killing hydraulic brake light switches when you switch to DOT-5 fluid. I decided to mount a micro-switch on my pedal box and wire it in parallel to the hydraulic switch's wires. Later Minis (and probably Midgets) used a pedal box mounted mechanical switch for the brake lights so this change made sense to me. If you're not after originality you could do the same.
 
OK guys, you are great, the green purple connector on the brake switch was defective. 10 minutes to trouble shoot and 10 minutes to fix...WOHOO BRAKE LIGHTS !! Now on to turn signals, but that will have to wait. I have commitments all week, and saturday she is going to the paint shop. Rover Metallic British Racing Green. The HArdtop will get a new coat of metallic black, and a new coat of white inside. SO Sunday or next week I will get to the turn signals. Right now though everythings else WORKS !!!
 
Way to go, rock on.
 
[ QUOTE ]
There was a link (now gone) on the Buckeye Triumph web site that discussed how to make new shuttles for these valves and what seals to use with them.

[/ QUOTE ]

Moss sells a rebuild kit for these for about $5 or so. Basically, it's the 2 o-rings on the shuttle that fail,and then the swotch will leak out the center where the plastic switch goes. When I re-did my brakes for DOT5 I replaced these o-rings as well.

Sure beats $500 for a new assembly!
 
Looked this up in "the book" intresting fitting that. Not sure what good it would do but still.
 
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