R25 Speedo
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Thread: R25 Speedo

  1. #1
    Fellow Frogger! Ren25's Avatar
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    Default R25 Speedo

    Need some advice here folks
    I have an R25 with a feugo manual 'box conversion. The electronic speedo is driven by a sensor mounted on the outside of the LH diff housing, which in turn is triggered by a sort of ring with holes in it mounted on the driveshaft. The speedo has gone to lunch and I need to know how to test the sensor or pickup.
    There are 3 wires coming off this pickup. I have delved into the dash area and can't see anything wrong visually, so next step is to see whether the pickup is putting out anything. Please don't say "occiloscope" or anything like that 'cause I don't have one, OK
    Cheers
    Mike

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  2. #2
    farmerdave
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    Quote Originally Posted by Ren25
    Need some advice here folks
    I have an R25 with a feugo manual 'box conversion. The electronic speedo is driven by a sensor mounted on the outside of the LH diff housing, which in turn is triggered by a sort of ring with holes in it mounted on the driveshaft. The speedo has gone to lunch and I need to know how to test the sensor or pickup.
    There are 3 wires coming off this pickup. I have delved into the dash area and can't see anything wrong visually, so next step is to see whether the pickup is putting out anything. Please don't say "occiloscope" or anything like that 'cause I don't have one, OK
    Cheers
    Mike
    Oscilloscope
    I take it is the r25 sensor on the conversion, yes?
    From memory the resistance between two of the conductors should be about 2 ohms, the third is a screen. The pickup is just a coil of very fine wire potted in epoxy and a plastic case.
    The sensors are pretty tough and only die if you dismantle them or burn the cable on the exhaust, I'd suspect the speedo itself.

    Farmerdave
    Last edited by farmerdave; 14th April 2005 at 10:08 PM. Reason: Resistance between the red and white wires is 1.84 ohm on a new cable

  3. #3
    Fellow Frogger! Ren25's Avatar
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    Default R25 speedo

    Bugger. Anyone got an R25 dash sitting around?
    Geez Dave, for a farmer you can spell real good.
    Thanks for the advice
    Mike

  4. #4
    1000+ Posts Europa's Avatar
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    Quote Originally Posted by Ren25
    Bugger. Anyone got an R25 dash sitting around?
    Geez Dave, for a farmer you can spell real good.
    Thanks for the advice
    Mike
    If you find one "just lying around", can you grab the GTX trip computer for me please. I'd like to try and go metric :-)
    '05 Pearl Black Mégane 5-Door LXR(Daily Driver), '75 Trak Yellow R16TSA (Parts Car), '74 Midnight Blue R17TS (Rebuilding), '73 457 Blue R17TL (Parts Car), '72 Alpine White R16TL (Retired), '69 Sunburst Brown R16TS (Awaiting Rebuild), '68 "Appliance White" Europa (Stored)

  5. #5
    1000+ Posts alan moore's Avatar
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    If you happen to know of a Renault repairer with an XR25 Renault test box, this can be directly plugged into the speedo to test its' operation. The R25 speedo will most likely have the standard complaint for these cars of "dry" solder joints and can be fixed by DIYer.

    I had most of my R25 electrics pulled apart a few times and found this to be the case. I sold the car about 10 years ago and see the owner at The Grand Display of French Cars each year. He has never had any faults with it since he bought it, bar the Air cond. Bit of a record for a 25, or just a well cared for car with a sympathetic owner.
    '56 Renault 4CV (16TS Power)
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  6. #6
    1000+ Posts silverexec's Avatar
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    I had an issue with our R25 speedo not working - the problem turned out to be a dry joint on the PCB inside the speedo. Check out this thread:

    Dodgy R25 speedo

    As for testing the cable, the only way I found it could be done reliably was with a... yep, OSCILLOSCOPE - a portable one I borrowed from a mate and hooked up to the car while we took it around the block. Other than that, yeah, checking the resistance is a basic test you can do - I measured about 3 ohms on my cable when I tested it.

    Cheers,
    Richard
    - Richard

    Now: 405 SRI D70 '93
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    Earlier: 505 GTi Executive '85
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  7. #7
    Member 25 V6 TURBO's Avatar
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    got a complete 25 turbo dash in the shed somewhere,and an xr25 on the way!!

  8. #8
    Fellow Frogger! Ren25's Avatar
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    Default speedo

    Thanks for your input guys
    Tomorrow I will once again take the bull by the horns and go forth into the valley of death, (take out the dash) and do a bit of continuity testing. The bloody thing will *not* defeat me, well not yet anyway. With the pleece farce so hot on the real criminals over here ie. those axe murderers who drive at 3km/h over the limit, it's very hard driving on the tacho.
    Mike

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