Subject: [TR] TR6: gauge LEDs and headlight switches

From: "Tim Gaines" <[email-masked]>
Date: Wed, 01 Dec 2021 16:52:25 +0000

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Despite some difficulties I'm making progress in installing LiteZupp=20
LEDs into the instruments in my 1974 LHD TR6. The difficulties stem from=20
my (possibly foolish) decision to do the job without removing the dash.=20
With the help of a couple of long-reach needle nose pliers I've replaced=20
the two illumination bulbs in each of the speedo and tach and the single=20
ones in the temperature and oil pressure gauges, not without several=20
scrapes to my fingers. However, I really don't think that will work with=20
the fuel and temperature gauges on the right. There are just too many=20
obstacles, so something is going to have to be removed, likely either=20
the radio or the glove box or both. It looks to me as if the glove box=20
space would provide the best access, but I have read of some=20
difficulties in getting it back in place after removal. I would=20
appreciate any advice from those who have done these bulb replacements=20
or taken out the glove box.

In the process of doing this bulb job I came across another problem. The=20
new LED for the high beam indicator just wouldn't light, and it didn't=20
matter which of the new LEDs I put in. So I went back to the old=20
incandescent bulb and it didn't light either despite having worked a=20
short time earlier. After checking the wiring to the socket and finding=20
no issues I decided that the problem must be the iffy headlight dimmer=20
switch on the right side of the steering column. I say "iffy" because=20
occasionally I had found that switching to high beam left me with no=20
headlights at all! I took off the plastic cowlings and got access to the=20
switch though I couldn't pull it out because its wires are clamped=20
within a channel under the steering column. Nevertheless, I could pivot=20
the switch out to get a narrow view of its innards and insert the thin=20
nozzle from a can of WD40, hoping for a lucky fix. The result was that=20
the switch, when re-attached with its retaining screws, would now pivot=20
toward me, something it never would do before. With the battery=20
re-attached as well, that pivot action produced a high beam flash that=20
also lit the beam indicator! I never knew I had a high beam flash in=20
this old car! So, everything was fixed!? Not so much. The light switch=20
on the dash wouldn't give me headlights at all despite the fact that it=20
would give me interior lights and the other exterior ones.

It was time to get out Dan Masters' guide to electronics, and as always=20
with this manual, I now understand the circuitry and my remaining=20
problem. When everything is working, the flash function of the dimmer=20
switch takes voltage from a fuse to the high beams directly regardless=20
of whether the light switch on the dash is set for headlights. When the=20
dash switch is set for headlights the voltage is taken directly from the=20
battery to the column switch that determines whether low or high beams=20
are activated. In following Masters' troubleshooting steps, I found that=20
my dash light switch was bad. It must have failed as I repeatedly=20
flipped it off and on to test all the new LEDs going in! I removed it,=20
verified with a meter that it was bad but managed to clean it up inside,=20
and it now tests okay. Today I plan to spray some electronic contact=20
cleaner (not just WD40) into the dimmer switch and hope that all of its=20
settings will work okay after I put the dash switch back in.

I'm sorry for the diversion into headlights. What I really want to know=20
now is how to get those last two gauges illuminated with new LEDs.

Tim
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<body>Despite some difficulties I'm making progress in installing LiteZupp=
 LEDs into the instruments in my 1974 LHD TR6. The difficulties stem from my =
(possibly foolish) decision to do the job without removing the dash. With=
 the help of a couple of long-reach needle nose pliers I've replaced the two =
illumination bulbs in each of the speedo and tach and the single ones in t=
he temperature and oil pressure gauges, not without several scrapes to my f=
ingers. However, I really don't think that will work with the fuel and temp=
erature gauges on the right. There are just too many obstacles, so somethin=
g is going to have to be removed, likely either the radio or the glove box=
 or both. It looks to me as if the glove box space would provide the best ac=
cess, but I have read of some difficulties in getting it back in place afte=
r removal. I would appreciate any advice from those who have done these bul=
b replacements or taken out the glove box.<div><div><br /></div><div>In the =
process of doing this bulb job I came across another problem. The new LED=
 for the high beam indicator just wouldn't light, and it didn't matter which =
of the new LEDs I put in. So I went back to the old incandescent bulb and=
 it didn't light either despite having worked a short time earlier. After ch=
ecking the wiring to the socket and finding no issues I decided that the pr=
oblem must be the iffy headlight dimmer switch on the right side of the ste=
ering column. I say "iffy" because occasionally I had found that switching=
 to high beam left me with no headlights at all! I took off the plastic cowl=
ings and got access to the switch though I couldn't pull it out because its =
wires are clamped within a channel under the steering column. Nevertheless=
, I could pivot the switch out to get a narrow view of its innards and inse=
rt the thin nozzle from a can of WD40, hoping for a lucky fix. The result w=
as that the switch, when re-attached with its retaining screws, would now p=
ivot toward me, something it never would do before. With the battery re-att=
ached as well, that pivot action produced a high beam flash that also lit t=
he beam indicator! I never knew I had a high beam flash in this old car! So=
, everything was fixed!? Not so much. The light switch on the dash wouldn't =
give me headlights at all despite the fact that it would give me interior=
 lights and the other exterior ones.=C2=A0</div><div><br /></div><div>It was =
time to get out Dan Masters' guide to electronics, and as always with this =
manual, I now understand the circuitry and my remaining problem. When ever=
ything is working, the flash function of the dimmer switch takes voltage fr=
om a fuse to the high beams directly regardless of whether the light switch =
on the dash is set for headlights. When the dash switch is set for headlig=
hts the voltage is taken directly from the battery to the column switch tha=
t determines whether low or high beams are activated. In following Masters' =
troubleshooting steps, I found that my dash light switch was bad. It must=
 have failed as I repeatedly flipped it off and on to test all the new LEDs=
 going in! I removed it, verified with a meter that it was bad but managed t=
o clean it up inside, and it now tests okay. Today I plan to spray some ele=
ctronic contact cleaner (not just WD40) into the dimmer switch and hope tha=
t all of its settings will work okay after I put the dash switch back in.</=
div><div><br /></div><div>I'm sorry for the diversion into headlights. What =
I really want to know now is how to get those last two gauges illuminated=
 with new LEDs.</div><div><br /></div><div>Tim=C2=A0 =C2=A0</div></div></bod=
y></html>
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