• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

T-Series brake switch

Share this page

TRMark

TRMark

Jedi Knight
Country flag
Offline
Many of the parts on my Cooper derived sports racer seem to be from T-Series. I decided to replace the brake switch, the one I ordered supposedly fits a TD but does not fit my application, the threads on the replacement look the same as my TR4. Original fittings are on the left. Ideas?


DSCN2327 (1024x768).jpg
 
A TF uses the same switch. The Chinese replacements are made cheap and have a habit of quitting unexpectedly. Solution to that is install a relay. I have a relay on my TF just for that reason. The switch activates the relay, the relay operates the lights. Probably need a fitting to convert the threads. PJ
 
What really kills those (and especially the PRC units) is the seal. Or lack thereof.

Brake fluid into contacts doesn't work well. In fact, Ford Explorers had a recall on switches for disengaging cruise, was a hydraulic switch like the ones shown, no fuse...and the brake fluid leaked into the switch, and in the middle of the night the car could torch off.

New switch and fuse for the line.

Ours has no cruise, has no switch, they did the recall anyway. Got a fuseholder with no fuse, the wire is taped off, goes nowhere.

Anyway, DOT5 will REALLY kill them fast.

I restored a 1950 Ford Convertible for a guy many moons ago, insisted on DOT5 in the all-new hydraulics...and he went about six weeks on each stoplight switch, until we finally did a non-hydraulic switch under the floorboards with an arm.

So it's an area of concern with DOT5 and especially aftermarket switches.

Your mileage may vary, depending on the age of the coil.
 
The difference in the threads may be that the new parts has NPT threads while your older switch may be BSPT. You can measure the diameters and thread pitches to confirm what you have. If you really want the original look you could probably chase the switch's NPT threads with a 1/8 BSPT die so the new switch fits your car's plumbing.

TOC mentioned the DOT-5 problem. I experienced the same DOT-5 switch failure he mentioned and implemented the same fix by installing a pedal actuated switch. I assume that since this is for your sports racer you are not running DOT-5. Regardless of the fluid type, you could leave the old switch in place with dummy wires for appearance and adapt a mechanical switch to the pedal box.

EDIT: For reference,
1/8 NPT is 0.405" outside diameter, 27 threads per inch.
1/8 BSPT is 0.383" outside diameter, 28 threads per inch.
While I would be surprised to find those threads were straight, there is a slim chance they could be either 3/8-24 or M10x1.
 
Back in 1965, the switch went out on Dad's 57 XK140 and the local Brit dealer could not get one, so he went to a local parts store (very unlike the ones today) and sat down with one of the parts guys and found that a 1953 Chevy Belair used the exact same switch. Something to think about. P.S. Jag brakes were Girling.
 
There are three three way fittings on the car. One of the legs on one of the fittings is stamped UNF, the switch leg. All the rest are 1/8 bsp, since I am putting in new brake lines, I have the fittings. The UNF leg is 3/8-24, the slim chance, I checked it with a bolt this morning. Think I will use the 53 chevy suggestion, I will let you know. So as a matter of curiosity, what is the thread on the supplied replacement, which is the same a the TR4. I installed a mechanical switch on the TR4 years ago, it would be difficult to do on this car, so at this point I am stuck with the hyd switch. I am not using DOT5 in the sports racer. The hyd master cylinder are mounted low, little paint to ruin. I found the DOT5 I used in the TR4 was difficult to bleed.

New Master Cyl View (1024x768).jpg
 
Wow, thanks Doug. That is exactly it.
 
Back
Top