The original instrument bulbs are all 2.2W. I have asked before what the
current consumption of these halogen bulbs is but got no response. Be aware
that the rheostat is pretty marginal at the best of times and increasing the
current by some 350% - if that is what it takes to power these halogen
bulbs - won't help. The rheostat dissipates the greatest heat when the
lamps are on about half power. But the closer you adjust it to full power
the higher the power density (heat per unit resistance) gets, which is why
they tend to burn out close to the minimum resistance point. However the
rheostats I have dismantled have been of the printed-circuit type, and these
'fail safe' to a certain degree by partially increasing the resistance at
the 'minimum' point as they burn out, so reducing the current and the power
dissipated, which stops further burning out. This gives the characteristic
'dim glow' - although they were never that bright in the first place. I
suspect many rheostats are in this state, which means that halogen bulbs
will never get the full power that Jeff recommends unless you replace or
bypass the rheostat. And if you are going to do that you may well find the
correct bulbs, plus cleaning them and the glasses and possibly painting the
inside of the cans, become bright enough to avoid the expense of halogen.
Particularly if they are not going to last that long anyway by being run at
part power.
PaulH.
----- Original Message -----
From: <LBCarCoMail@aol.com>
To: <fwp@ufl.edu>; <mgs@autox.team.net>
Sent: Saturday, November 04, 2000 1:29 AM
Subject: Re: Light bulbs
>
>
> Frank,
>
> About 2 years ago I read a tip on using the 7v (I think it was) bulbs in
the
> MGB. I went to RS and bought a bunch of them and gave some to some
friends
> too (they are still friends but not happy campers ;))).
>
> In any case as you may know it is not a lot of fun replacing the bulbs in
a
> B (I found removing the tack or speedo helps as you can then reach through
> the open hole), After we all replaced the bulbs we were so excited as we
> could then read the instruments. Well about 2 weeks later my first bud
> called me that the bulbs were burned out. He went back to the std bulb
(he
> is also an electrical engineer and has a wonderful website dealing with
MG's
> about electrics). My bulbs all burned out too about 3 days later.
>
> Your best bet is the 12v 5w or 10w halogens (the 5 w for the smaller
> instruments and the 10 w for the tach and speedo). I have them in all
three
> of my MG's (EmmieA, EmmieB and Maggie) and they work great. I can even
read
> a map in a pinch with my tach and speedo when Jan is sleeping on our
weekend
> jaunts. Just keep in mind you cannot handle the glass with your hands or
> that will limit their life and you also need to keep your reostat at high
if
> you have one as Halogens should burn at full power for longest life.
>
> Hope that helps.
>
>
> Best regards,
>
> Jeff Zorn
> Little British Car Co., Ltd.
> Visit us on the web
> www.LBCarCo.com
>
> In a message dated 11/3/00 3:06:22 PM Eastern Standard Time, fwp@ufl.edu
> writes:
>
> << Subj: Light bulbs
> Date: 11/3/00 3:06:22 PM Eastern Standard Time
> From: fwp@ufl.edu (Phillips, Frank)
> Sender: owner-mgs@autox.team.net
> Reply-to: fwp@ufl.edu (Phillips, Frank)
> To: mgs@autox.team.net ('mgs@autox.team.net')
>
> List,
>
> Sorry to hit the list with this but ListQuest is dead and I need info
that
> could come from the archive!
>
> I'm looking to replace the bulbs in my gauges and need the info on the
Radio
> Shack bulbs that fir the MGB. My car is a 68 and the lights that do work
are
> rather dim. I looked on a few web sites but did not find the information.
> Thanks...
>
> Frank Phillips
> 1968 MGB - http://plaza.ufl.edu/fwp/mgb.htm
> Email: fwp@ufl.edu
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