I’ve searched archives but could not find an answer for the
question if a Lucas RB340 Control Box/voltage regulator can
be substituted for an RB310 on an XK140. The previous
owner left the XK sitting for ten years with a rebuilt
engine, new wiring and a new RB340 on it. Since starting
the car, the amp gauge has not shown charge and shows heavy
discharge with lights on. The car has a new battery and
the generator is providing an output as tested with a test
light that gets brighter with higher revs. Given this, I
am not sure if I need to get a proper RB310 or what. Any
guidance from electrical minded members would be greatly
appreciated. Don–
Etch, Etype S1 coupes, XK140 roadsters, Lotus Evora, 911
Spring Hill. fl, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from Etch sent Sun 8 Mar 2015:
More information about this subject. The Lucas RB340
appears to be a solid state version in that the black top
cover does not have removable screws but more permanent
looking rubber plugs. It was sold by Moss Motors in the
year 2000 and I am not sure if it is setup for positive or
negative ground. The E or earth terminal is grounded to
the body of the car and the B is to the battery. So since
the KX140 is a positive ground, should these be changed?
The model on this control box says 37576, 12v 24 98 and has
a yellow sticker saying 30A. Thanks.–
Etch, Etype S1 coupes, XK140 roadsters, Lotus Evora, 911
Spring Hill. fl, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
RB340 & RB310 are electrically quite similar. RB340 is definitely not solid
state if by that we mean using semiconductors. The main difference between
the two model is the mechanical construction. Lucas say the RB340 is much
easier to adjust mechanically than RB310.
So, the short answer is yes, you could probably get an RB340 to work after a
fashion. It is important to remember that RB310 (or 340) is just the model
number and within that are variations designated by the part number. These
variations match the control box to a particular generator, expected vehicle
load, battery capacity etc. so if you want to use the unit you have you
should at least try to find a matching generator, presumably, with a 30A
output.
Eric
Church Stretton, UK-----Original Message-----
From: owner-xk@jag-lovers.org [mailto:owner-xk@jag-lovers.org] On Behalf Of
Etch
Sent: 09 March 2015 01:44
To: xk@jag-lovers.org
Subject: Re: [xk] Lucas Control Box RB340
In reply to a message from Etch sent Sun 8 Mar 2015:
More information about this subject. The Lucas RB340 appears to be a solid
state version in that the black top cover does not have removable screws but
more permanent looking rubber plugs. It was sold by Moss Motors in the year
2000 and I am not sure if it is setup for positive or negative ground. The
E or earth terminal is grounded to the body of the car and the B is to the
battery. So since the KX140 is a positive ground, should these be changed?
The model on this control box says 37576, 12v 24 98 and has a yellow sticker
saying 30A. Thanks.
Etch, Etype S1 coupes, XK140 roadsters, Lotus Evora, 911 Spring Hill. fl,
United States --Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
Etch,
The installed (more modern) control box should work fine and it probably
did before your car was “laid up”.
IMHO, you need to “routine” the contact “points” inside the cover. These
are very prone to build up an insulating layer of corrosion that will
even defy fairly rigorous cleaning with fine wet/dry sand paper.
I recently did a pair of these regulators and found that I actually
polished the accumulated corrosion to a smooth bright surface. However,
what visually looked like a clean contact was anything but! They still
did not conduct!
I’d suggest you disconnect the battery and get inside the regulator cover
and polish up the contacts. If the cut out (cut in) fails to conduct,
the Dynamo will show no charge to the battery. If the regulation/voltage
contact doesn’t conduct the dynamo field will always be at minimum,
resulting in a low output that will not satisfy the car’s load.
Regards, and please let us know what you find.
Rick____________________________________________________________
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