In alt.home.repair, on Fri, 21 May 2021 00:57:36 -0400, Clare Snyder
wrote:


Its certain that the problem is the programming, not the simple
electrical connections. The evidence for that is the delay you
see when covering and uncovering the photocell. That proves
that it isnt simple electrical connections driving what you see.

Even so, regardless of what the programming in the body ECU or elsewhere
is, where the wires go into the Clock, there has to be something at
night that provides power to those lights, or in the daytime, a signal
that tells the Clock not to light up.

I'm ready to rewire the car to make up for that.

In the first case, if I could figure out*** what pin provides the power
for the light during the night, I could hot wire** it to provide the
same power during the day.

In the second case, if I could figure out which pin the signal comes to
the Clock to say don't light up, I could cut that wire. At least until
I saw what else that disabled. It might be worth it, it might not.


I THINK it is the green and white wire on pin 18 - the "illum -" wire
- if Im right disconnecting will make he light stay off?

Makes sense.

This is ASSUMING it is not STILL just an issue of not having the
instrument panel dimmer adjusted properly which was my FIRST
suggestion months ago.

I don't remember ignoring that line but I've been busy lately and
haven't caught readers here up on a lot of projects in progresss. I
hope to do that soon.

Anyhow, the dimmer didn't solve my problem (even though it seemed to
solve the opposite problem for people asking questions on the web.

And there is no detent on this dimmer.

BUT WHAT IS REALLY INTERESTING I LEARNED LAST NIGHT. I went out at 2AM
to check the car, even though I was sleepy and didn't really want to,
because if I didn't, I'd have to have waited until the next night.

So... in the dark, when the taillight relay is bypassed so that the dash
lights** are on even in the daytime, and the Clock lights are on
(because it's dark) the dimmer controls the brightness of all the
lights, every one***

BUT, AND GET THIS BUT, when I remove the jumper wire**** so that the the
dash lights** are not lit, then the dimmer control has NO EFFECT on the
Clock lights. The lights are at full brightness.


So in a way the Clock lights are independant of the Dash lights, but
otoh, they're simultaneously controlled by the same dimmer. That took
some work on Toyota's part.


The dimmer wiring isn't shown in the wiring manual -- I don't think the
dimmer is shown at all and certainly not individual wires -- but now
that the speedometer is out and its back off, I can see a little box
1/2" cube, on the surface of the circuit board, directly behind the
dimmer knob. It has a short connector, 1" wires, to the ciruit board
with yellow, red, blue, and black wires. I think it might only need 3
wires if Toyota had wired all the lights the same and the fourth might
be related to the Clock.

But I don't know which wire is the fourth, and if I did I wouldn't know
whether to cut it or to ground it, or what. The circuitry is too
confusing to me, since sometimes the dimmer has an effect and sometimes
it doesn't. And it's too close to other wiring it could affect. OTOH,
if nothing else works I might come back and fool around here.


It is so complicated, and Toyota went to a lot of trouble to make it
work this way, when if they'd done nothing and wired the Clock lights
the same as the other panel lights, it would have made more sense IMO,
not just for me but for anyone. And it would have enabled me to easily
hotwire them.

I don't miss not having lights on the other dash lights during the day
time, because everything is visible anyhow. The instruments are moving
needles, or there are buttons that can't be missed. As to the shift
indicator, I rarely look at that. I know where I put the shifter. As to
the glove box light, I think it should be illuminated in the day time
too, but it's been 30 years since I hunted for something in the glove
box. It's only the clock and the mpg/etc. that I want to see, and
because they are the only LCD indicators in the car, these are the ones
I can't read.



**Speedo, radio, AC, and seat heater buttons, console gear indicator
light, and glovebox light.

***(FWIW, the clock lights start to dim a little behind the others but
they all get totally dark at the same point, or maybe almost totally
dark.)

****The jumper wire goes from one wire to another on a seat heater
switch, from 12volts when the car is running to the switch light and
from that wire to all the other dash lights. I've removed the Panel
fuse that would power all these things, so that the taillight relay is
closed has no effect. The power is totally dependant on whether the
jumper wire is in position.



**That's what I tried to do in the first place. I removed the Panel
fuse but ran a jumper from the "On-when-runing power to the Seat Heater
switch" to the Seat-heater-light. Now all those dash lights in parallel
with the seat heater light are on whenever he car is running, not just
at night.

I want to do something similar for the Clock, but... Pin 18 goes to
terminal Ill-, which stand for Illumination, but it's negative. I guess
the possitive is one of those fuses.

Hmm going back to the speedo cluster would make sense if there was a
dimmer control on the speedo, and in some of the toyotanation posts
about dashlight, they had success by twisting the dimmer knob past the
detent. But those cars were a year or two newer, and I don't have a
detent. If I twist any harder, I'll break it.

Still, maybe if I "hot"-wire Ill-, pin 18, that is, not making it bot
but grounding it, maybe that will bypass something in the speedo part of
the dash board. The wire is W-G and goes to the combinaton meter,
their word for the speedo cluster. There are in the wiring manual 160
instances of the word "combination". [-(

***I tried taking the Clock apart, but it was just a circuit board with
a chip and a few other parts.