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Re: TD Brake pressure switch gone bad??

To: MGs@autox.team.net
Subject: Re: TD Brake pressure switch gone bad??
From: "CHRIS KOTTING" <ckotting@wideopenwest.com>
Date: Mon, 9 Aug 2004 11:14:53 -0600
I hate to say it, Paul, but you're mistaken on this one, or at least not 
completely clear.

If the switch is still in circuit on both sides (i.e. both the from-the-
ignition-switch and the to-the-lights wires are connected) then the voltage 
dropping to 0 when the switch is actuated may be perfectly OK.  IF the wiring 
to the ligths is intact and the bulbs are in place, then when the switch is 
actuated the voltage potential between either terminal of the switch and 
ground will drop to near zero (possibly too small to measure on a 12 volt 
voltmeter.)  However, voltage isn't the entire issue.

What I suspect is that the switch is closing the contacts, but isn't passing 
enough current (amperage) to light the lights.  Solution 1 is to replace the 
switch, and do it again when that switch degrades to the same point.  

Solution 2 is non-original but remarkably effective.  Put a relay in circuit 
so that the brake light switch only has to pass the few milliamps required to 
fire the relay, and the amps required to light the lights pass through the 
relay contacts.  The additional advantage of Solution 2 is that your brake 
lights will be noticeably brighter.

If I remember correctly, the TD in question is in Columbus, Ohio.  Roger, if 
you want a hand, drop me a note directly and we'll see if we can work out  a 
time to get together...

Chris K.


-----Original Message------
Date: Mon, 9 Aug 2004 09:33:28 +0100 
From: "Paul Hunt" <paul.hunt1@blueyonder.co.uk> 
Subject: Re: TD Brake pressure switch gone bad?? 

I'm no expert on TD brake lights but if you have 12v on one wire when the 
brake pedal is released, and 12v on *neither* wire when the brake pedal is 
operated, it indicates a bad connection back towards the ignition switch. 
On an MGB the culprit is often the fusebox. 

PaulH. 

> ----- Original Message ----- 
> From: "Roger Wilt" <rdwilt@pol.net> 
> To: <mgs@autox.team.net> 
> Sent: Sunday, August 08, 2004 3:23 PM 
> Subject: TD Brake pressure switch gone bad?? 
>
> ... At 
> the switch, I have 1 hot wire (goes into the old harness) and 1 dead 
> wire(runs back up toward the engine compartment). When the brake is 
> depressed, the power is gone from the hot wire according to voltmeter, but 
> no power to or from other wire... 


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