i just finished setting up my guages. all the wiring is good and the guages switch on and everything. I have the dimmer and the light wire connected to the ashtray light. They are only connected to one of the wires leading to the light. Do they need to be spliced into both of the light wires to dim? Also do the autometer boost guages dim or is that a constant light? oh and 1 more thing. Where can i buy those self tapping screws that come w/ the mounting pod? I had to cut mine to remove the pod and now i'm out of them. I checked the local pep boys and autozone and they don't have the right sizes. any suggestions on this?
thanx

 

That's a bit confusing... "dimmer" and "light" wires? I assume you're using non-LED lighting, right?

The ashtray light has a TNS switched constant 12V source (R/B) and a dimmed (pulsed) ground (R/G). You gotta use both. If they aren't dimming, it sounds like the light is getting the positive from the ashtray and a constant ground somewhere else.

 

your gauges wont dim with the stock ones unless the aftermarket gauge has a seperate ground for the light. in that case connect the lights ground to the ashtray ground.

as insanegideon said the lights are dimmed by pwm on ground. if you connect the gauges common ground to this then the display will be wrong.

 

Translation from electronics geek to "layman" - pwm: pulse width modulated i.e. ground is connected then opened repeatedly and rapidly - the connected time vs the open time is varied - the longer it's connected the brighter the light.

You have to be careful not to connect that signal to the car ground, as all the lights will then go full bright. The dimmer module beside the radio does all this - it's electronic.

Yeah, I'm an electronics geek.

To make it work, make sure the gauge lights are not grounded to the car on either side. Connect power to the lights (use ashtray line if you like). Connect the ashtray ground line to the gauge light ground. This will also work just fine if you have LED lights.

If your new gauge lights are brighter than the rest of the lights in the dash, add a resistor in series with the +12V supply to the lights. You'll need to use a power resistor for that - and mount it so it will not burn anything if it gets too hot.

 

alright thanks. the guages are grounded to the car and not to the ashtray light. also if an led guage doesn't have a dimmer wire if you put it's ground on the same wire as the astray will it dim w/ the dimmer light?
thanks for the replys

 

i got the whole mechanical guage dimming set up now, thanks for your help. upon reading my last it seems unclear. I have a cyberdyne led water temp guage. it has a seperate wire that the instructions specify as a dimmer wire. it is purple. the instructions say to attach this to the switched light source constant +12 volt wire. I tried this and it would not dim. it was at full bright. the ground on this guage is a seperate ground not connected to the ashtray lamp. so then i connected this purple wire to the ground wire from the ashtray light. when i do this with the dimmer at full brightness the guage is fine, but as soon as i use the dimmer switch, the guage starts going crazy and flashes random numbers. how do i wire these electronic guages to dim with the stock guages? should i just ignore this purple dimmer wire and use David Beales suggestion?

 

So Cyberdyne specifically asks for a "constant (not dimmed) 12V" to activate the dimming?

When you connected the dimming wire to the switched light source (TNS), it should've gotten darker, regardless of how the dimmer was set. You'd only have the two brightnesses (lights on and lights off) as this takes the dimmer completely out of the loop.

Since they specifically mention a constant +12, I'd stick to that, no resistor or anything. They probably have some internal circuitry, like an internal pulsing dimmer of it's own, to make the LED darker when you turn the lights on. The car's dimmer may be introducing noise to the meter circuitry, or it may be otherwise confusing the gauge since it's expecting a constant 12V.

Dont feel bad, my DEFI Link has limitations too. It can accept a dimmed +12V, but not a dimmed ground, since the lighting shares ground with the electronics. I was going to use a transistor to convert a pulsed ground to an inverse pulsed 12V, but I stopped caring at some point.

 

alright thanks anyways and thanks for the replys guys. i'll just wire it at full brightness. im about at the point where i dont care either just as insane gideon said.