[TR] TR250 LED tail light problem

[Roger Elliott]

I decided to give up on the issue.

There did not seem to be much of a voltage drop across the battery - 
about .05 volts as near as I could make out.  It's possible that either 
the meter or myself were not quick enough to read accurately.

As far as I could tell there is not a ground terminal on the sockets.  
There was about .009 volts between the lamp housing and the battery.  I 
did run additional wires from the lamp housing to a ground (to the tank 
mounting bolts).

The brake/tail lights still varied with the turn signals, in opposition, 
got brighter when the turn signals were off.

Tested the lights with regular brake lights instead of LEDs. I noticed 
the brake/tail lights still varied with the turn signals. This is when I 
decided to give up and just live with it.

Oh, the third brake light that I have wired in - power from the brake 
lights and grounded to the body flash when ever the brake lights and 
turn signals are on (like the brake/tail lights in opposition.

Thanks for your help.
Roger

On 11/3/2019 4:37 PM, Randall wrote:
>
> Yes, that’s the idea.  You want all the lights on (including turn 
> signals) during this test.
>
> What you’re looking at is how much voltage drop there is through the 
> ground path.
>
> -- Randall
>
> *From: *Roger Elliott <mailto:elliottr at rmi.net>
> *Sent: *Sunday, November 3, 2019 1:26 PM
> *To: *triumphs at autox.team.net <mailto:triumphs at autox.team.net>
> *Subject: *Re: [TR] TR250 LED tail light problem
>
> HI Randall,
>
> Thanks for the information and the tests.
>
> I just want to check something on the tests since my electrical 
> trouble shooting ability is very limited.
>
> This section is also done with the lights on, right?:
>
> To check for grounding issues, I suggest running a wire to the 
> negative battery terminal or negative starter cable, so you can 
> connect the ground lead of your DMM to that.  Then you can probe at 
> the rear lights, to see how well they are actually grounded.  0.2 volt 
> is probably acceptable, anything more than that represents a problem 
> that could be fixed.
>
>
> Thanks,
> Roger
>
> On 11/2/19 4:07 PM, Randall wrote:
>
>     There may not be a good solution, Roger. The incandescent turn
>     signals draw a fair amount of current, which is likely more than
>     the stock alternator can deliver (along with tail lights and so
>     on) at idle.  So it may be that the battery voltage is dropping
>     from 13+ volts (alternator supplying all power to car) to  12.6
>     volts (battery supplying some of the power) and the LEDs you’re
>     using are sensitive enough to show the difference in voltage.
>
>     To check, connect a good voltmeter or DMM to the battery, then
>     watch what it does when the tail lights and flashers are both on. 
>     If I’m right, you’ll see the battery voltage sag in time with the
>     turn signals.  The only fix would be to convert to a more modern
>     alternator, that can keep up with the lights at idle.  (I’m not
>     certain, but I think there is a Lester unit that would look and
>     fit the same as the stock Lucas but give more current across the
>     board.  Check with the Jaguar folks.)
>
>     Another fix might be LEDs that use an active current source (so
>     are much less sensitive to supply voltage), but I have no idea
>     where to buy such things.  I made my own using a simple
>     2-transistor active current limiter.
>
>     To check for grounding issues, I suggest running a wire to the
>     negative battery terminal or negative starter cable, so you can
>     connect the ground lead of your DMM to that.  Then you can probe
>     at the rear lights, to see how well they are actually grounded. 
>     0.2 volt is probably acceptable, anything more than that
>     represents a problem that could be fixed.
>
>     I’m not sure how the TR250 tail lights are wired.  On my TR3, all
>     the rear lamps ground only through their mounting screws, which go
>     into clip nuts fastened to the sheet metal.  Very insecure,
>     especially if the sheet metal has a fresh coat of paint.
>
>     However, each lamp has a terminal inside the housing for a ground
>     wire.  So, I made up a ground wire that daisy-chains across all
>     the rear lamp holders, then leads around the trunk to one of the
>     fuel tank mounting bolts.
>
>     -- Randall
>
>     *From: *Roger Elliott <mailto:elliottr at rmi.net>
>     *Sent: *Friday, November 1, 2019 12:50 PM
>     *To: *triumphs at autox.team.net <mailto:triumphs at autox.team.net>
>     *Subject: *[TR] TR250 LED tail light problem
>
>     Here's the problem.  When the tail lights are on and I use the
>     flasher,
>
>     the tail/brake lights flicker with the flasher.  They don't go on and
>
>     off but the get brighter and dimmer. When the third brake light is
>
>     hooked up it does the same thing.
>
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