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MG TD TF 1500 - Brake Light Switch

This is the TD Newby again. the other thread was getting kinda long.

We have brake lights!! Installation of the switch was relatively easy with no loss of fluid or pedal.

Esoteric question though: I just received my "official" mg td-TF shop manual and I looked in it for any hints no replacing the brake light switch (there were none) and I noticed that in the schematic for the brake system in the manual the switch is mounted on the top of the 4-way connection roughly under the driver's seat. In the catelogues from Moss and in some other places it's always mounted on the botom of the 4-way and my old switch was on the botom. I had thought about putting it on the top to avoid fluid loss (turns out that waws unnecessary) but discovered that without serious modification of the dar or relocating the 4-way, this was not going to work - insufficient room for theswitch and it would have been impossible to get to the screws to clamp the wires. Does anyone know if the factory mounted the switch on the top or the bottom of the 4-way?

Thanks.

Jud
J K Chapin

The drawing in the factory manual is wrong. Artistic license? Drawing of a prototype chassis? There are a couple other mistakes in the manual, I can't remember what they are at the moment. George
George Butz

Thanks George. I though mounting on top might prevent sludge build up that could impair the activation of the switch but I couldn't figure out how to do it.

Jud
J K Chapin

I've been using hydraulic brake lamp switches from Ron Francis Wiring which are billed as "low pressure" switches and give a faster activation of the stop lamps. Not cheap but I think worth it for the advance warning time. Fitted one recently to my Morris Minor and 1965 Jaguar sedan.
John Quilter (TD8986)

John Quilter talks about the Ron Francis brake light switch (P/N SW-32). It is the only switch that will not fail in a short period of time after installation. Switches available today, either from Moss or NAPA will fail in a short period of time. This has been an ongoing problem with all MGs for quite some time - seems that the replacement switches available today (with the exception of the switches sold by Ron Francis Wiring (http://www.ronfrancis.com/) are junk.

The other alternative to the more expensive, Ron Francis Wiring switch to get a brake light switch that will last is to make or purchase a relay/arc suppression circuit and add it in series with the brake light switch. For information on making or purchasing the circuit, see the article, Brake Light Relay in the Other Tech Articles section of my web site at: http://homepages.donobi.net/sufuelpumps/ Cheers - Dave
Daved DuBois

All,

My brake light switch failed last weekend after almost 20 years. I ordered a new one from Brown & gammons in the UK. I mentioned to the salesperson that there seems to be a problem on the failure rate on these, he told me that the ones they sell do not have this, and in any case they are guaranteed for one year so I went ahead and ordered one. I don't want to add a relay circuit
(for the same reason that I don't want to put a 7.2 liter V8 engine in my car.) just to workaround junk switches.

John

52 TD
J Scragg

According to their website, the Ron Francis low pressure hydraulic brake switches have 1/8" pipe threads. For those of you who have used them, how have you adapted them to fit the the 4-way fitting? The threads aren't compatible, are they?

Joe
J.W. Olson

"For those of you who have used them, how have you adapted them to fit the the 4-way fitting? The threads aren't compatible, are they?"

They are compatible. The 4 way fitting is also 1/8 pipe thread. Not sure about the hole for the switch, the other holes are 1/8 British Standard pipe (parallel). The switch (and the original switch is 1/8 tapered - I'm not sure if it is USPT or BSPT, but the switch screws into it and seals right up (there is only one thread difference between BSP and USP. Since 90+% of brake light switches (including the ones from Moss all have the same thread). Cheers - Dave
Daved DuBois

In my post above, I used the wrong designation for US pipe threads. Instead of USPT I should have used NPT and instead of USP, it should be NP. Cheers - Dave
David DuBois

This thread was discussed between 20/11/2012 and 21/11/2012

MG TD TF 1500 index

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