TR2/3/3A Why is my brake light continuously on TR3A

[Got_All_4]

Did a complete brake job front to back. Now when I turn on the ignition on the brake lights come on and stay on. Could I have the rear brakes adjusted too tight and that is butting back pressure in the system and kicking the switch on?

 

[TR3driver]

No, that wouldn't do it. Either there is an electrical short, the switch has failed, or the return valve in the MC is not opening as it should. I'd start by checking the pedal and pushrod adjustment, especially if your car has the pedal stop screw.

 

[Don Elliott]

Check that the two wires to and from the hydraulic brake switch are connected correctly and both wires are not touching each other.

 

[Got_All_4]

Well loosened up the pedal push rod so there was a 1/4" play and the light stayed on. I then loosened the main brake line in the front hole in the brake master cylinder thinking if the pressure was relieved and if the return valve was not operating properly, the switch would release and the light would go out. Well the light stayed on. So sould I assume it's the switch?

 

[TR3driver]

Next step, look carefully at where the wires are attached to the switch, make sure there isn't a stray strand of wire creating a short. If you can't find anything, then try pulling one wire off the switch. If the lights go out, replace the switch.

But it seems unlikely that a brake job would make the switch fail; and I've never had one fail closed. So I'm still suspicious that there is something else going on.

I got so frustrated with the original switch that I installed a mechanical type switch (as Triumph did for the later cars). Wouldn't make it past a concours judge, but with it so far under the dash, most people won't notice the difference:

 

[Got_All_4]

I'll double check the wires tonight. Do You know what threads are on the switch? I would want to plug the hole so the fluid does not drain out while I work on the switch.

 

[MGTF1250Dave]

Aloha,

I believe the threads are NPT 1/8 x 27, and they are pretty common to your brake hydraulic system. You can get a replacement brake light switch at NAPA for about $13 or so. The part numbers are ECH SL144 (with screw terminals) or ECH SL143 (push on blade terminals).

here is a link to the screw terminal switch:

https://www.napaonline.com/Catalog/CatalogItemDetail.aspx?A=ECHSL144_0160679465&An=0

 

[TR3driver]

I believe the threads are NPT 1/8 x 27,

Another way to reduce fluid loss is to prop something to hold the brake pedal slightly depressed, just enough to close the inlet valve in the MC. I have a cheap bar clamp with the jaws reversed that works well.

 

[Got_All_4]

Thanks! I wonder if they have the blade type too. However I already call my Triumph supplier today and he has the correct one in stock. I'm so blessed to have him in my back yard. He sells Moss at a discound and has multiple barns FULL of used stuff. I'll pick it up tomorrow with my E brake stuff.

 

[Got_All_4]

Well it looks like the switch. I pulled the switch and pluged the hole with a 1/8 pt grease fitting. There is current going accross the terminals.

 

[MGTF1250Dave]

Here is a link to the one with blades:

https://www.napaonline.com/Catalog/CatalogItemDetail.aspx?A=ECHSL143_0307178585&An=0