1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Tach Light not working

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Old Sep 18, 2008 | 12:03 AM
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Tach Light not working

I started my car and was about to go out for a drive today at night, but i found out my tach and all my interior lights are not working. What can cause this problem? Thanks for the help
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Old Sep 18, 2008 | 12:54 AM
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Have you done the usual trouble shooting like checking the fuse?

and the tach doesnt work at all? or the light.... becuase tach not working is usually trailing coil or ignitor or w/e
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Old Sep 18, 2008 | 12:55 AM
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I checked them, and they all look fine. Which one should I double check on?
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Old Sep 18, 2008 | 01:37 PM
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Checked all the fuses again... they all look good.
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Old Sep 18, 2008 | 01:50 PM
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Have you recently had the shifter boot off? If so, did you connect the wires under there that don't appear to go to anything? Those are for the illumination for A/T shifter. Connecting those blows out the dimmer switch. These either fail to where you have no interior lights or lights at full brightness.

Another possibility is the position on the dimmer switch got bumped. Try to turn up the brightness and see if the lights work.

What about the dome light? Does it work? If no, then you are probably looking at a loss of power (blown fuse, disconnected wire, etc.). If the dome light works, but dash lights don't, then the dimmer switch is probably toast.
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Old Sep 18, 2008 | 01:54 PM
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Haha... i did connect those 2 wires together. What can I do now?
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Old Sep 18, 2008 | 02:31 PM
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Hehe. I think that almost every 7 owner does that at some point. Mazda should have used a 2-pin connector there instead of bullet connectors. I guess they didn't figure on the M/T RX-7 owners trying to plug them together.

So first thing you need to do is to unplug those wires.

You have a couple options for the repair:
1. replace the dimmer with a good used one
2. bypass the dimmer (there are thread on here that tell you how). This will cause the interior lights to run on full brightness (no dimming available)
3. repair your current dimmer switch. If you take it apart, there is a transistor in the back (largest component in there). That is what typically blows in my experience. Drop in a new transistor (NPN if I remember correctly) and it should be fixed.
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Old Sep 18, 2008 | 02:48 PM
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Originally Posted by gsl-se addict
Hehe. I think that almost every 7 owner does that at some point. Mazda should have used a 2-pin connector there instead of bullet connectors. I guess they didn't figure on the M/T RX-7 owners trying to plug them together.

So first thing you need to do is to unplug those wires.

You have a couple options for the repair:
1. replace the dimmer with a good used one
2. bypass the dimmer (there are thread on here that tell you how). This will cause the interior lights to run on full brightness (no dimming available)
3. repair your current dimmer switch. If you take it apart, there is a transistor in the back (largest component in there). That is what typically blows in my experience. Drop in a new transistor (NPN if I remember correctly) and it should be fixed.
Thanks... I will look into the cheapest option first... #2
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