Modified RX7 dimmer control

posted Sep 15th 2009 10:00am by
filed under: transportation hacks

SANY00191

We were a little surprised when we learned the Mazda RX7′s high beams were controlled by ECU, compared to typical cars using just a toggle switch. Ubermodder [Trent Bruce] realized how much of a pain in the rear end this can be if the ECU ever burns out, meaning no brights. By using a D-Flip Flop setup in a toggle configuration, he is able to control his once lost high beams. He also points out that if you plan to do any other electronic modifications to the RX7, you should be sure to pay attention to the unusual ground switching and the other crazy wiring under the hood.



17 Responses to Modified RX7 dimmer control

  • DanAdamKOF says:
    September 15, 2009 at 10:05 am

    I’d assume with RX7s being as “reliable” as they are that you’d need to do lots of crazy hacks to keep them running normally ;)

    Clean hack though, and great writeup.

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  • Jack says:
    September 15, 2009 at 10:37 am

    I’m more of a gear head than a hacker, and i know my imports and my only question is if your ECU burnt out i’ve got a feeling the car would not even run anymore, the ECU is pretty important, but he could just get a AEM stand alone ecu, tune it all to hell, 900cc injectors and a turbo, say what? dude i want an RX7 pretty bad

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  • JD says:
    September 15, 2009 at 10:43 am

    Say what is right.

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  • Matt says:
    September 15, 2009 at 10:54 am

    @DanAdamKOF I always heard that the rotaries are very reliable, but Mazda would put 5W-20 in them to meet US emissions regulations. Overseas they use 5W-30 and do not have reliability problems.

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  • Aaron says:
    September 15, 2009 at 10:55 am

    I agree… if the ECU died the least of your problems would be your brights. The car wouldn’t start anymore.

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  • ChopShop says:
    September 15, 2009 at 10:56 am

    Yeah, was gunna say….no ecu = no vroom vroom. So pointless hack.

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  • Andar_b says:
    September 15, 2009 at 11:36 am

    Huh: It may be a hack, but it can’t be the ECU that’s burnt out! Nothing else would work either, so this hack doesn’t matter.

    Everyone else: Don’t posters who type in all caps make you yearn for the days of all lowercase on HAD?

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  • Matt says:
    September 15, 2009 at 11:53 am

    Maybe it’s not the ECU but some other controller?

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  • twistedsymphony says:
    September 15, 2009 at 12:24 pm

    reading his writeup I get the impression that it’s a separate circuit from the actual ECU and that this hack replaces said circuit.

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  • MattM says:
    September 15, 2009 at 12:29 pm

    It very well may be that the ECU is fried. It wouldn’t be the first time that an output circuit controlled by a microprocessor/controller has fried, leaving the rest of the unit working. Like most things on cars these days, they only sell it as a single unit so you have to pay more for parts.

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  • Hitek146 says:
    September 15, 2009 at 12:56 pm

    ^That…

    The MOSFET in the ECU that switches the current to the high beams probably just burned. That doesn’t mean that the car wouldn’t run anymore…

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  • JJ says:
    September 15, 2009 at 1:29 pm

    @ChopShop

    Don’t you mean Zoom-Zoom?

    Reply Report comment
  • Alec@ubermodder says:
    September 15, 2009 at 3:52 pm

    I agree with everyone, the ECU isn’t burned out, just the high beam logic circuitry. The reason for it stopping could be cracked solder joints or broken vias. And the ECU may start working again after a good solder reflow.

    We’re just glad we made it to Hack a Day =)

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  • wa11yba11s says:
    September 15, 2009 at 4:26 pm

    There is a dedicated latch circuit that is inside the ECU, and I don’t have the engine running off of the RX7 ECU cause this little lady is v8 converted.

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  • Nonya-Biz says:
    September 15, 2009 at 5:00 pm

    the RX-7 has alot of computers, but i think this circuit is in the “CPU” (a crap relay computer in the drivers side kick panel)

    i have one with a street ported 13b i had the “CPU” crap out. nearly got run of the road with no horn.

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  • AbortRetryFail says:
    September 16, 2009 at 3:25 pm

    I’ve got an 86 RX7. It’s the “CPU” in the driver’s side kick panel as Nonya-Biz said. That little box isn’t hard to get out and fix though, it was probably bad solder joints as these cars are notorious for that…

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  • someone says:
    September 17, 2009 at 12:02 am

    RX-7 are definitely reliable once you work out all the gremlins. My RX-7 TurboII has 257k miles on it. The engine has ~200k miles. It was replaced before I owned it at about 56k. I have always run 10w-40 Valvoline.
    If you buy a used RX-7 you better have some mechanic skills though cause as I said they do have gremlins. Definitely, replace the fuel pressure regulator and pulsation dampner. They tend to leak fuel and cause engine fires.

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