Modified RX7 Dimmer Control


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 thoughts on “Modified RX7 Dimmer Control

  1. 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

  2. @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.

  3. 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?

  4. 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.

  5. 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 =)

  6. 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.

  7. 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…

  8. 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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