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MG MGB Technical - Brake Light Switch
|I changed my master cylinder in my 74.5 MGBGT. When all put back together I experienced problems with my brake lights; staying on then not going on at all. I have adjusted the switch several times and set at several distances but now I have no brake lights. What am I missing here? Get a new brake light switch or....? Thanks, JOHN|
|Remove the switch drom the cover and operate the plunger by hand. If the brake lights work with every stroke you have an adjustment problem, if they don't, order a new switch.|
|Wouldn't think that changing out you M/C would cause your brake switch any harm. Experience suggests that such things usually result from either improper adjustment or a bad connection (missed connection). |
Have you pulled yours and tested it? If I remember correctly (it's been years), circuit is on with ball plunger out and off with plunger pressed in. That is (assuming all else is correct), if switch is screwed out - brake lights should come on (test). If working, then screw in until brake lights go off and tighten lock nut. Again - if my memory is correct - might have it ass-backwards. Course, one should check for 12 V to the switch at the start - should have 12 V at green wire from fuse box. Thinking, another check might be to disconnect switch and jumper the two lead wires to switch and see if brake lights come on.
|Not sure if this is the same setup as a 68B or not, but I had the same problem and found out there was a difference in the spacers for the pedal shaft and when I re-assembled after master cylinder rebuilds, my brake pedal did not contact the switch. I placed the spacers and pedals back in the correct positions, and everything worked. That was a newbie moment. Anyhow hope this helps.|
|John - There are good suggestions above, particularly Edwards regarding the pedal/spacer positions. After exhausting everything else, if you find that the switch is bad and you have to get a replacement, be aware that all the replacements available today are extremely light duty and will fail after a short period of time (I had one fail after only two weeks) due to the contacts burning. You can make the replacement switch work for many years by installing a relay/arc suppression circuit. Instructions for making and installint this circuit are available at: http://www.omgtr.ca/technical/brakelightrelay/brakelightrelay.htm|
Cheers - Dave
|The comments have been helpful. My switch appears out. Now, Where can I get a new switch which is not light wieght and without having to construct a relay? Thanks, guys.|
|John - I don't know of anyplace that carries a switch that is heavy duty, but someone on the board may know. There is really nothing to putting together a relay/arc suppression circuit and it will make even the light duty switches that are readily available last a lifetime. Cheers - Dave|
This thread was discussed between 07/05/2007 and 09/05/2007
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