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Re: [TR] alternator conversion in a tr3

To: <triumphs@autox.team.net>
Subject: Re: [TR] alternator conversion in a tr3
From: "Randall" <TR3driver@ca.rr.com>
Date: Tue, 2 Jun 2015 22:49:02 -0700
Delivered-to: mharc@autox.team.net
Delivered-to: triumphs@autox.team.net
Thread-index: AdCduRpUZMpX20eaTjeKCoEhHVigxwABjFgw
> It is a long story, (don't ask it hurts,) but in reality a 
> LED bulb will not 
> complete the charging circuit at low engine revs under 2000- 
> 2500rpm. Fact.

An easy solution for that problem (sorry, Dixie) is to add a resistor in 
parallel with the lamp.  The resistor is a good idea anyway
(IMO) in case the bulb ever burns out (or fails to make contact).  I had one on 
my TR3A with alternator conversion, simply soldered
to the back of the bulb holder but sticking out a bit to keep the heat away 
from the plastic.

Also, some alternators (the ones that can be used in a "one wire" 
configuration) will not exhibit the above problem.

However, there is another potential problem with the ignition warning lamp; 
which is that it can see substantial reverse voltage.
Not all LEDs can withstand that much reverse voltage without damage.  So a 
series diode may also be required.  The diode may also be
needed if you have an electronic ignition that has it's own power feed, like an 
MSD 6A.

There are also some TRs where the turn indicator lamp operates with both 
polarities (eg 69 TR6).  They will also need some
modification to use an LED for the indicator (in addition to the mods to use 
LEDs as turn signals).

-- Randall  


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