Dimmer for instrument lights

[William Andersen]

Anyone know what I need to buy to add a dimmer to my instrument lights?
I want to be able to control the intensity of my instrument lights. They are
not shielded and reflect on the windshield, making it impossible to sit and
look through the windshield. We have to stand while at the wheel at night.
I've changed to red light bulbs, but the instrument panel is tilted so much
there's no way to shield the windshield from the reflected light.
I went to a Radio Shack today and all they could come up with was to offer a
volume control knob mounted on a wall switch plate. Since I'm not a techie,
I need to know exactly what to ask for, since they seem to know even less
than me.

 

[Dennis Pogson]

Anyone know what I need to buy to add a dimmer to my instrument
lights?
I want to be able to control the intensity of my instrument lights.
They are not shielded and reflect on the windshield, making it
impossible to sit and look through the windshield. We have to stand
while at the wheel at night. I've changed to red light bulbs, but the
instrument panel is tilted so much there's no way to shield the
windshield from the reflected light.
I went to a Radio Shack today and all they could come up with was to
offer a volume control knob mounted on a wall switch plate. Since I'm
not a techie, I need to know exactly what to ask for, since they seem
to know even less than me.

You need a voltage controller. I think you may get one at a car accessory
shop.

 

[William Andersen]

Thanks for the link - more expensive than I expected, but something to look
into.

 

[William Andersen]

Thanks for the reply - I'd rather have a dimmer switch with continuous
range, so that I could turn the lights up or down to any intensity. They are
not LEDs. They are controlled by the ignition switch. Whenever the key is in
the on position, the instrument lights are illuminated. I've added two other
lights to that circuit because it was easy to access; I'll wire them
differently when I add a dimmer so that they won't be affected. It's just
the instrument panel lights that are reflected on the windshield.

 

[WaIIy]

Anyone know what I need to buy to add a dimmer to my instrument lights?
I want to be able to control the intensity of my instrument lights. They are
not shielded and reflect on the windshield, making it impossible to sit and
look through the windshield. We have to stand while at the wheel at night.
I've changed to red light bulbs, but the instrument panel is tilted so much
there's no way to shield the windshield from the reflected light.
I went to a Radio Shack today and all they could come up with was to offer a
volume control knob mounted on a wall switch plate. Since I'm not a techie,
I need to know exactly what to ask for, since they seem to know even less
than me.

Four years ago I bought one from Searay for about $45.00.

The dimmer was pretty heavy duty and worked perfectly.

 

[William Andersen]

Holy cow! $45: I might forget about this idea.
Thanks.

 

[Jack Erbes]

Anyone know what I need to buy to add a dimmer to my instrument lights?

<snip>

Just about every automobile has one, I'd visit a wrecking yard and
probably look for one of the newer ones that has the dimmer control
mounted separately from the light switch (like a dash mounted thumbwheel).

Jack

 

[Johnhh]

Or go down to the hardware store and buy a light switch dimmer. It would
probably rust out in short order, but I'll bet the resistance would be close
enough to work.

 

[William Andersen]

Why not?

No, that won't work at all.

 

[Rusty]

Hardware store dimmers only work on AC power, not DC. They use a solid-state
device called a Triac, not a variable resistor.

Blue Sea makes dimmer units in several different amp ranges for 12 and 24
volt DC systems specifically for this type of application. They also sell a
switch to control it already labeled "Bright" and "Dim". These are available
through West Marine and several other distributors. I have one installed in
my custom engine instrument panel and it works like a champ.

Rusty O

 

[Johnhh]

I guess I just always assumed they were just variable resistors. There I go
assuming again--it gets me every time. Were they ever made with variable
resistors?

How do the Blue Sea one's work?

 

[Rusty]

The Blue Sea dimmers are about two by three inches and about one inch thick.
They have five wires coming out one end. These wires go to 1) Ground, 2)
Power, 3) Bright, 4) Dim, 5) Light. The wires themselves are labeled for
their use. The switch you use to control the dimmer is designated (ON) OFF
(ON).

(ON) means 'Momentary On' so the switch returns with a spring when you press
on the top or the bottom and returns to the middle OFF position when you
release it. Switches like this connect a circuit from the center connection
to the bottom connection when you push on the top of the switch. They
connect the center position to the top connection when you push on the
bottom of the switch. Note: This is backwards to what you might expect.

To wire the dimmer you connect the 'Ground' lead to DC negative, the 'Power'
lead, and the center connection on the switch, to DC positive. The 'Bright'
lead connects to the bottom of the switch and the 'Dim' lead connects to the
top of the switch. The 'Light' lead goes to your light bulbs and of course
you connect the other end of each light bulb to DC negative. Don't forget
that DC positive lead to the center connection of the switch, it won't work
without it.

Now when you push on the top of the switch the lights will get brighter and
when you push on the bottom of the switch they will get dimmer. Another good
feature is the dimmer will 'remember' the last setting and return to it if
you turn off the power and later turn it back on again.

These dimmer units are available in 2 amp, 5 amp, and 10 amp versions. They
can also be used to control the speed of DC powered fans.

If you just want a simple rotary knob dimmer, Cole Hersee makes two
different models also available through West Marine and several other
suppliers. These, and the low amp Blue Sea system, all run about the same
price.

I answer to Johnhh's question, home dimmer switches haven't been made with
variable power resistors in more than thirty years.

Rusty O

 

[Ed]

A very cheap solution would be to put a resistor in series with the
lights and an SPST switch in parrallel with the resistor (to short it
out). You need to figure out the resistance on the chain of bulbs, find
a suitable similar resistance (for 1/2 power... more for less light,
etc) Power rating needs to be figured out as well. For 1/2 power, it
should match the total of all the lights... less if you raise the
resistance.

THis doesn't give you the variable resistance but it is a couple dollar
solution that may solve the problem.

 

[Rusty]

If the main goal is to see how cheap you can do it....

Try painting the bottom contact on each light bulb with resistance paint. If
it's still too bright, just add another coat.

Rusty O

 

[William Andersen]

I don't deny being cheap. But I was looking for variable control.
I guess this will wait - there's better things I can do with $45