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Triumph TR6 - Brake failure sensor

We picked up a '73 Tr6 earlier this summer and I've been gradually working off the little things that the previous owner had learned to live with but I wanted to take care of. The latest is a brake warning light that's always shining brightly. I checked the sensor on the brake line itself and found that there was only one wire coming out of the harness although there were two pins on the sensor itself. It looks as though the other wire broke off at some point but I can't tell if it is supposed to connect to the same spot that the first wire connected to. so, question #1: Are there supposed to be two wires and if so, do they connect to the same spot a few inches from the harness?

I figured that I was on the way to fixing the light problem but I can't determine if the switch itself is working properly or not. I checked both pins with a ohmeter and they both have continuity to the frame. question #2: If the switch is working properly should only one of the pins have continuity or is it possible that they both have it?

The wiring diagram in the shop manual wasn't much help, it only shows one wire coming out of the switch and doesn't suggest that there are two pins.

Any help would be appreciated,
thanks

John Tarby

Hi John

1 wire is all there is.

The unit has a piston inside that if centered IE both back and front brakes having equal pressure the light stays off. If either side of the system fails the light goes on because the piston moves to that side.

Here is a good troubleshooting guide and how to.

http://www.buckeyetriumphs.org/technical/Brakes/Troubleshooting/Troubleshooting.htm


Bill
Bill Brayford

For what it's worth, the warning light also lights for low oil pressure. Until I fix/re-center my PDWA I'm just leaving it disconnected. At least I have a half-wit idiot light!

Charlie
EC Smith

Bill, I gotta thank you. I've been playing with my darn Brake Failure Light since I purchased the car, and after replacing the wiring harness, it was still the ONLY item that refused to co-operate. That is...until you pointed to this article on the PDWA valve. It's the only place where there is a reference made to the wiring on a '76. It's the only year where the Brake Failure Bulb is not wired in series and does not extinguish with the oil pressure light. ARRGH!! At least I now have piece of mind that it's working properly. tks

Mati
Mati Holland

Bill,
I finally had a chance to play with the PDWA and discovered that it was simply not centered. I pulled it out and tested the switch, that worked fine, then used a nail to recenter it. With no pressure in the line it moved back to center with no problem.
One less headache, thank you.
Also, since the PDWA switch has plastic threads it didn't have any rust problems and came out without a fight. If your brake light is on and you've been putting this off I'd encourage you to give it a shot.

Thanks again,
John
John Tarby

Hey John and Mati good to hear.

One tip thats not on there and would apply to anyone using ramps or jack stands bleeding brakes. Most often the car will be fairly level but if its not?

Please observe the picture of the reservoir angle in the master cylinder rebuilding section. The large rear section has to be full to overflowing before the front section for rear brakes will get anything after doing a complete purge. Thats if the car is level!

Cars level "reservoirs tipped foreward". Fluid runs into the front for rear brakes. Cars not level fluid runs on floor first. If your reservoirs are like my 72 its very hard to see the level of the front one for rear brakes. Plus at that time I didn't know how the stupid thing realy worked. Used to 2 pot visable system.

Filling I was getting very little in the front before I quit pouring. Not wanting it overfull while bleeding in case of bubble splash on paint. Bleeding the rear of course I was running out of fluid but the reservoir was still full to the eye.

Spent a full day sorting that out and another full day figuring out the PDF red light business afterwards. PDF cylinder was so far foreward I needed a team of oxen to pull it back..:)

My Uncles used to say the boy ain't all that bright! But if you beat it into him it tends to stick...:)

I admit to stupidity and plead a dark garage. That was about 87 somewhat prior to public internet.

Bill
Bill Brayford

This thread was discussed between 23/08/2004 and 28/08/2004

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