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MG MGA - Brake Light Switch


I've read lots in the archives but is there anything else that could affect the hydraulic brake light switch ? I've replaced it and when the leads are "shorted" the lights work...just another bad switch ?
I can't imagine anything else that could affect it ...
DA MacFarlane

DA - You are afflicted with a malady that has infected a great number of MG owners from TD through MGB - crappy replacement switches. You have two choices (three if you consider extending the left arm out the driver's side window pointed downward to signal people behind you that you are stopping - remember those days?). You can get a very expensive hydraulic switch from Ron Francis Wiring P/N SW-32, which should last for as long as you own your car, or you can get one of the crappy switches from M/M, V/B or local auto parts store and make and install a relay/arc suppression circuit at the same time you install the switch. You can see instructions on making the relay/arc suppression circuit by going to the article, Brake light Relay in the Other Tech Articles section of my web site at: Cheers - Dave
David DuBois

With apologies to DA for slight variation in his thread I wonder if David DuBois could advise on the occurrence and reason for loud clicking from the relay after installation of a brake switch relay as per his wiring diagramme.
J H Cole

David, great link, that doesn't seem so expensive, considering it will work! I just hope that we can develop a database of quality components like that. I remember something about good quality rotor arms too, from Jeff Schlemmer at advanced distributors. Are they still available?
Neil McGurk

Thanks Dave,

I've ordered one..although when I emailed to ask if this part would work with a 1961 MGA - he replied "no idea " !
DA MacFarlane

DA - "I've ordered one..although when I emailed to ask if this part would work with a 1961 MGA - he replied "no idea " !"

I am sure that at Ron Francis Wiring they don't have the specs to say if something will work with a particular vehicle, but I don know of at least one person who installed the switch in his MG (I think that it was a MGA, but am not positive). I can say, however, that all the MGs, from TD to early MGBs that use the hydraulic brake light switches, will work with the SW-32 switch, in that they all use the same switch (with just the wire attachment being different (TD & TF using grub screws and MGA & MGB using spade lugs).

JH Cole - Please contact me direct at with the problem you are having. I will need more information before I can hazard a diagnosis. Cheers - Dave
David DuBois

MGA uses grub screws originally.
R J Brown

Did the TD and TF halve different threads? MGA has 1/8 pipe thread. All MGA's used grub screws with the possible exception of some of the late 1600 MkII's. That being said, the Ron Francis switch should work if it has 1/8 pipe thread, but the wiring will have to be modified.
James Johanski

All hydraulic brake light switches use 1/8 pipe thread, regardless of the vehicle. Cheers - Dave
David DuBois

This thread was discussed between 16/07/2009 and 19/07/2009

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.