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Discussion Starter #1
Hi everyone,

I'm having an issue with the clock light on my 2006 RAV4. When the headlights are off, the clock is nice and bright - when I turn them on, the light goes off.

So, I decided to go into the instrument panel to see what was going on, and oddly, when I removed and disconnected the 4WD control and 4 way flasher panels, with the headlights on, the clock light suddenly got bright! When I plugged them back in, it went out again.....

What could be the issue? Is there a relay that's messed up, or what? I'm baffled....

TIA,

bobster
 

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Discussion Starter #2
I forgot to mention that the dimmer switch works for all of the dash lights, but has no effect on the clock light.

I also just noticed that the on-off indicator light on my rear defroster doesn't work either (the defroster does work, however). Maybe the two are related somehow?
 

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2008 RAV4 Limited V6
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What about the 4WD LOCK button? Does it light up? Does the clock light up only when BOTH the LOCK button and the 4-way flasher buttons are disconnected, or only one of them? If only one of them, then that switch would be the problem.
 

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Discussion Starter #5
The 4WD drive back-light on the switch works, but does not get brighter once turned on (the indicator light in the instrument panel does light up).

The 4 way flasher backlight works, and the lamps all work normally when it's turned on.

Here's the sequence (all with headlights ON)

- clock light works great when both the 4WD switch and 4 way flasher are disconnected

- clock light dims significantly when 4WD switch is plugged back in, but is still there, although quite faint

- clock light disappears entirely once the 4 way flasher switch is plugged in, at the same time with the 4WD switch

- clock light disappears entirely with the 4 way flasher switch plugged in, regardless of whether or not the 4WD switch is plugged in

I hope I'm being clear!

Thanks!
 

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Did you happen to install an aftermarket stereo head unit, alarm system, or any aftermarket equipment? I will study the schematic and get back to you.
 

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Discussion Starter #7
The only thing I have installed on the car is a trailer harness. It plugged into the taillights, and I ran a positive wire directly to the battery...
 

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The clock, the 4wd switch, the DAC switch, the hazard switch, and quite a few other lights are all in parallel.

When the headlights are turned off, all the lights in question receive 12 volts, and according to you they all work fine. Therefore there is no problem with the lights or the wiring.

When you turn on the headlights, the current flowing through the lights is limited by the position of the dash dimmer control.

Since all these indicators are LED's, it is possible that the voltage required to trigger them on, varies by a few millivolts from one to another. It would appear that your dimmer control is only allowing enough current for the LED's with a lower trigger voltages to turn on. When you remove a LED that has turned on ( the 4wd or 4 way flasher) the voltage increases on the clock LED and it turns on.

If you increase the brightness using the dimmer, the clock LED should eventually fire up. Are you saying that the clock LED does not work even when the dimmer is set to maximum brightness?

When you place the dash dimmer control into the indent position, all the LEDs should once again receive 12 volts and turn on fully. Have you tested if this is true in your case?
 

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Discussion Starter #9
When the headlights are on, the clock light is completely off (no light at all) regardless of where the dimmer switch is set, including the indent position.

When the headlights are off, the clock light is as bright as it can be.
 

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Discussion Starter #10
Should the backlights for all the switches get brighter when the dimmer is in the indent position?

When I turn it to indent, the only thing that gets brighter is the instrument cluster light. Everything else stays as it was before.

Does your schematic say whether or not the rear defroster switch is in parallel with the clock? The backlight works, but when turned on, the little rectangular light in the center doesn't get brighter, as does the air conditioner light, or the air recirculation light (the defroster still works, however).

Maybe they're unrelated, but I figured I'd tell you, in case they are......
 

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Should the backlights for all the switches get brighter when the dimmer is in the indent position?
First let me say that I wish I could see how my RAV actually behaves, but I no longer have it, so I am basing my comments strictly on the wiring diagrams.

LED's run at low voltages, nominally at 1.7 volts. If they are used in a 12 volt circuit like the RAV, they either require a resistor in series with LED to drop the voltage, or a voltage regulating circuit to reduce the 12 volts down to 1.7 volts.

The wiring diagrams do not show the presence of dropping resistors, but sometimes when a resistor is integrated into a switch, they are not shown for simplicity.


LED's normally do not dim very well. They only turn on when their forward voltage is applied (1.7 volts) and only get somewhat brighter as the voltage is increased to the point that damage would occur if the voltage increased any further.


It looks like the RAV4 has a "LED Driver" circuit that provides the voltage for all the LEDS. In your case it looks like this circuit is not providing enough current to power all the LED's at the same time. So for example if the LED on the 4WD switch turns on at 1.6 volts, the limited current flows through this LED and not enough voltage is available to turn on the clock LED wich requires 1.7 volts. When you unplug the 4WD switch, then enough current is available to tun on the clock LED.

Now having said that, it appears that the LED Driver is working properly when the headlights are off. That adds confusion to the diagnosis.

Further testing would be required to confirm this theory. If you have a voltmeter measure the voltage across the clock's LED with the headlights on and off ( the green and light green wires). Then measure it with the 4WD switch plugged in and out. I'm fairly certain you will read the lowest voltage when the headlights are on and the 4WD switch is connected.


BTW, the rear defroster "operated" indicator is not part of the dashboard illumination circuit. Did the clock trouble start at the same time the defroster indicator stopped working?
 

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Discussion Starter #12
IIRC, the rear defrost "on" light was out well before the clock light problem started.

I will check the voltage on the clock light, as you suggest, and get back to you either the results.
 
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