TR6 TR6 PDWA switch help please

[ichthos]

My car has been sitting for a year. After driving for a week, the brake light came on. I checked, and everything in the breaking system seems fine. I rebuilt the entire brake system before it sat, but didn't touch the PDWA switch. I have one of the original brass switches. It appears there is some crud in the switch. I am guessing the piston is stuck, but I am not sure. Are these switches easy to rebuild? I was confused by the moss catalog. What kit would I order to rebuild this? Any help would greatly be appreciated.
Kevin

 

[MGTF1250Dave]

Aloha Kevin,

Here is a link to "Brosky's" website that details rebuilding the PDWA.

https://www.74tr6.com/pdwa.htm

 

[tdskip]

Don't be shy with questions Kevin, great to see you getting her sorted out.

 

[ichthos]

Thanks, Dave. I quickly looked through his article and got all the info I needed. Top notch work from Brosky as always.

 

[poolboy]

The crud might be the only problem. It was with mine a while back.It was just crud that bridged the gap between the 2 contacts in the plastic switch that screws into the brass PDWA.
When the crud bridges the contacts, the ground is completed and your dash BRAKE light comes on, same as it would if the shuttle within the brass PDWA shifts to one side or the other due to a pressure imbalance in your brake hydraulics.
So just remove and clean the plastic plug before you attack the PDWA and the shuttle O-rings.

 

[ichthos]

The kit is not that much. I think I will clean things as you suggested, Poolboy, and if everything looks OK I won't worry about it. That way I will have a kit in reserve just in case.
Kevin

 

[poolboy]

Yeah, that shuttle shouldn't shift on it's own.
If it does shift, it would be because you have a leak in the brake line, caliper, or rear brake cylinder and the light would come on as a warning.
But crud alone can bridge the contacts and also cause the light to come on, with no problem in the braking system.
Clean the plastic switch good, inside and out.

 

[hondo402000]

More than likely your PDWA has shifted, the two prongs in the switch both do the same thing, you can use either pin for the hook up, if both pins are touched together you still will not get a ground connection, the actuation pin in the switch has to be pushed up by the shifting of the PDWA plunger to make a ground, which turns on the light. I replaced the Switch in mine and figured that out when I went thru my rewiriing process, YOu can unscrew the switch and see if the piston in the PDWA has moved off center and to check to see if the switch is bad, unscrew the switch, leave the wire hooked up. manually operate the switch by pushing the actuation pin in against the block or a bare metal part which will complete the ground, if the light comes on the switch is good, and then most likely your PDWA has shifted, depending on which way the piston moved will tell you if its the front or back brakes that are the problem. I hope you understand this I read it over and over

Hondo

 

[Scott_Hower]

depending on which way the piston moved will tell you if its the front or back brakes that are the problem. I hope you understand this I read it over and over
Hondo

All good stuff.

I think the PDWA splits the circuit on a diagonal; left front+right rear are on one circuit, right front+left rear on the other.

 

[poolboy]

No, it's strictly front or rear.
And just to be clear about what might just need cleaning, I wasn't talking about the gap between the 2 pins that Hondo described, but rather the contacts within the switch that the plunger normally bridges in case of a pressure differential.

 

[DougF]

You may have difficulty removing the piston. If a good soaking of penetrant and hitting it on a block of wood doesn't do the trick and all of your options are exhausted, call Scott Harper at Team Triumph. He has several on the shelf that have the piston removed. (330)392-7176