Electrical question

[JNC]

Tonight my brake lights don't work !! They did when I left home but not on the return journey ? . I checked the brake light switch and found the contacts were burnt, I scratched clean the two contact faces and they work again , My question is why do they burn and carbon up ? obviously it's like arc welding  this is not the first time I've had to do this how can I stop it happening ?.

[Jonathan Kay]

They're passing more current than the contacts like. 

Could reduce the current with a relay... or fit LEDs... or think of the switches as consumable...

Jonathan

[JNC]

Would a smear of Vaseline help ?

[Jonathan Kay]

I don't think so... and the windows might fall out.

Jonathan

[Ian B]

A search should find a much better quality replacement switch from Car Builder Solutions 

[sjmmarsh]

Ian B - the Car Builder ones really work! I ordered one when my standard plastic one failed at the MOT. I cleaned the plastic one up to get the car passed rather than wait for the CBS replacement. The plastic one is still in there 6 years later....

Steve

[JNC]

Windows !! I know it's late but that one has passed me by 

[Ian B]

Steve

[SM25T]

Old tv joke involving putty and vaseline .... 1970s.

[JAL]

John, our cars seem to mimic each other perfectly. I drove home last night with no brake lights!

Can someone point me in the right direction for the correct replacement switch from CBS please?

Doug

[Brian27]

John

I had the same problem and had to clean up the switch contacts, however; I found that the switch adjustment had been set too fine against brake pedal travel. This meant that the contacts were not fully opening with no pedal travel. Switching a DC current will always produce an arc across the contacts and cause them to burn up. By adjusting the mounting nuts on the switch so that it needs a little more brake pedal travel before the contacts make, cured the problem.

Brian

[JNC]

Doug did my car catch it from yours or vice-versa ??. I have removed mine and completely stripped it down  cleaned the contacts with wire wool and reassembled after spraying with electrical contact cleaner ! . I will post some photos later. I have found the supplier it's ( Intermotor , Part No 51470 )

[JNC]

Photos of brake light switch if you haven't seen one before.                           

I stripped the switch down and cleaned all the metal parts with wire wool then checked that all realigned, then sprayed all the inside with contact cleaner operated the plunger then refitted and adjusted then tested all now working          I have ordered a spare from CC just in case.     

[JAL]

Cheers John,

I'm not sure who caught from who. Perhaps they are coming out in sympathy for each other!

I'll try to clean it this weekend (weather permitting) and I've also ordered a new one just in case. I would still be interested in a more reliable type from CBS if anyone has any recommendations.

Thanks again

Doug

[JNC]

Doug , when you remove the end to access the contacts use a Stanley  knife to lever the side out  don't forget it's under pressure from the spring , not a lot but enough to send it across the garage !.

[JAL]

Many thanks John,

I now have working brake lights again. Strange that the switch contacts looked like new when I took it apart but I cleaned and reassembled anyway and it all worked instantly.

This was officially my first Caterham repair so I appreciate your help. 

Doug

 

[Jonathan Kay]

Well done, John.

... not a lot but enough to send it across the garage... 

Spoilsport!

Strange that the switch contacts looked like new when I took it apart but I cleaned and reassembled anyway and it all worked instantly.

With good contacts and a sufficiently springy spring that could have been a sticking plunger. But you know how to sort it now. :-)

Jonathan

[aerobod - near CYYC]

For a permanent fix to avoid contact burning on the brake light switch, I would suggest fitting a relay, as the arcing produced at the contacts by the more than 3A brake light circuit can reduce the switch life considerably compared with less than 100mA with a relay.