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Re: WARNING TRF Bodge / MGB Ign lite

To: sol <british-cars@autox.team.net>
Subject: Re: WARNING TRF Bodge / MGB Ign lite
From: Randy Wilson <randy@taylor.infi.net>
Date: Sat, 22 Oct 1994 18:05:26 -0400 (EDT)
Paul Swengler proclaims:
> 
> I havn't figured out why the brits put those damn brake warning switches 
> in. After your brakes fail you are supposed to believe a lucas electrical 
> warning lite will save you from eminant doom?? GIVE ME A BRAKE!
> 

The British put "those damn brake warning switches" in because your loving
federal government thinks that you do not have enough sense to figure out
the brakes failed when the pedal bounces off of the floor. All cars sold in 
the U.S. market starting in 1968 have to have a brake failure warning light.
To date, there have been three stratigies. The most common is a differential
valve between the two brake systems. When one side gets pressure, but not the
other, the piston moves, the switch trips, and the light comes on. Another
is to put a float switch in which trips when you run out of brake fluid.
The third is to mount a switch to the floor. Pedal hits the floor, triggers
the switch, and the light comes on. Of these three, the differential
valve is the only one that will warn with a half (one side) failure.

 I'll leave the uninformed shot at Lucas alone for now. Read on.


> Nigel has eaten about six of those little plastic warning switches. Every 
> time I roust about a recycler I pick up the plastic inserts and a month 
> or two later they leak, the brakes go soft and the light doesn't come on.
> 

I'll bet you every one of those six switches was good. The switches weren't
designed to be fluid tight at several thousand PSI because they should 
never see brake fluid at all. What has happened to you is the one or both
of the seals on the differential piston has failed, allowing high pressure
fluid into the center switch well. This causes two things. First, the fluid
leaks out through the switch. Second, the light will not come on because
you now have a hydraulic lock inside the valve body. the piston can't move
if equal pressure is being applied to both sides.

 So, you now have six non-Lucas switches that didn't fail. 

> (P.O. training instructions deleted)
> 
> The early generator cars didn't have very sophisticated electric and wewe 
> dangerous! My son's TR-4 melted the amp gauge and the regulator in about 
> three seconds and damn near set the car on fire. When we replaced the 
> wiring we:
> 
>       THIS IS IMPORTANT>>>
> 
>               We added a flat 40 amp fuse in the
>               line (large Brown wire) between
>               the generator and the regulator.
>               I believe it was the "F" terminal.

 Hmmm, this leaves me asking three questions:
    1> What originally shorted out enough to kill 10guage wire?
    2> What caused it to short?
    3> How is putting a 40 amp fuse in the isolated output line of a 17 amp
        generator supposed to help?

   Randy



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