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Today at Atelier Kaz - Private NSX Enthusiast, ex-Honda R&D engineer with F1, Indy/CART background

Carpet, Interior Panel, Health Check, etc 12

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As reported in the last post, on very rare occasion, I noticed that the Parking brake indicator and the ‘BRAKE LAMP’ warning light stayed On immediately after turning the IG key into P2 but even before touching the brake pedal.

This will happen if you disconnect the right tail assy or if you have wiring or gauge assy issue.
Normally with the gauge issue, the first sign is the intermittent BRAKE LAMP warning even with good light bulb and I don’t think the parking brake circuit would be affected so decided to first check the 22pin grey connector at the forward left section of the boot behind the carpet.




With the state of the tail light assy gasket before replacing them with the new one, no surprise several terminals showed heavy corrosion. 2 x male terminal turned into green patina corrosion, 3 x female terminal lost the internal sprung force and making intermittent connection.






Polished the male terminals and replaced all three female ones with gold plated one.

However, all five were not related to the brake light (they were for the rear fog light, power ANT) and also I checked all of the terminals at the R & L tail light assys and none of them showed any issues……


I’m afraid the issue is the wiring issue somewhere on the car but most likely to be the gauge assy internal issue with leaky capacitor.
I can replace the caps but don’t have the jig to re-calibrate the speedo and rpm gauge so at this stage, can’t do much.

Without the brake disc, can’t do anything any further on this NSX so moving onto the next NSX.


Kaz










Comments

  1. greenberet's Avatar
    Dear Kaz, if the problem with replacing the capacitors in the gauge assembly is re-calibration, maybe there is a relatively simple solution. There is a speedometer calibration how-to posted on NSX Prime (https://www.nsxprime.com/wiki/Speedometer_Calibration) that mentions four adjustment potentiometers at the back of the gauge assembly and which one is for the speedometer. Perhaps a GPS speedometer could serve as a speed source during calibration. For the rev signal, perhaps data from the OBD II could be used or an external tachometer hooked up to the pickup loop in the engine compartment. For the other two pots: ?
  2. Kaz-kzukNA1's Avatar
    Hi, greenberet. Thank you for the suggestion.

    VSS signal is defined in JIS and all Japanese production cars must follow it so it's not difficult to program PIC or even write simple software for me for the calibration purpose as part of my background is eng/chassis control.
    I'm afraid if you follow the procedure in Wiki at NSX Prime, you will introduce larger deviation at certain speed range. You must use all four pots to calibrate speedo and rpm gauge.
    You also need to manually change the mechanical calibration of certain gauges by moving some parts on the gauge assy.
    I just need to figure out the most cost effective way to deal with different circuit board design for each model years and different spec.
    Already spoke with T3TEC about building another jig for me but they are flat out since last year with so many things to be done so I don't want bothering them for my own requests.
    Depending on the demand and market size, I may consider owner's funding to pay enough for them to spare some time for the jig.
    I need to check my gauge assy any way as it's showing about 10kph lower figure for the first 15 - 30min driving at 60mph until I slow down a lot and then back to 60 - 70mph again to show the correct reading. Typical sign of caps failure.

    Kaz
  3. greenberet's Avatar
    Dear Kaz, that's good to know even if it's not good to hear. My speedometer displays a bit less than a GPS speedometer at low speeds but I never thought to check whether that changes over time. I'm sure you'll have plenty of customers whenever you move forward with a jig. Come to think of it, there should be lots of demand for this service in North America as well - even if they don't know it yet.
  4. Kaz-kzukNA1's Avatar
    Speedo is on purposely calibrated to show lower speed at higher speed range by the car manufactures so not sure whether your phenomenon is an issue or just the result of this on purpose 'adjustment' especially, I don’t know what is the ‘low speed’ for your NSX after watching your epic flatout video several years ago….

    Gauge assy is such a delicate item that I don’t like sending back and forth outside of UK.
    I'm thinking of hand carrying mine to Japan in the future or create molded container with X-ray protection.

    Even for the nearby European owners outside of UK, I only deal with a/c CCU board or audio head unit with agreement that I won't take any responsibilities for the loss/damage of the package to/from my place as I'm quite sure they are passing strong X-ray inspection or even MRI level inspection these days….
    My a/c oil was detected and being stopped by Japanese Customs even it had full documents allowing the airmail delivery. Eventually, it was sent out from Japan after explaining the documents and contents but still, shows the level of checks they are doing on even a small package.....
    Updated 18-05-2016 at 10:29 AM by Kaz-kzukNA1 (extra info)
  5. greenberet's Avatar
    Dear Kaz, yes, here in Europe there is a regulation regarding how the speedometer must be calibrated. European Council Directive 75/443/EEC states "The speed indicated must never be less than the true speed." The relationship between the indicated speed (V1) and the true speed (V2) shall be 0 ≤ V1-V2 ≤ V2/10+4km/h at 40, 80, and 120 km/h.

    Unfortunately, my speedometer is breaking the law - it does indicate less than the true speed. At least around town. Maybe I should just drive faster.