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How To Test Out Odometer??


plyzo
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Hello guys,

 

My current odometer is not working and when I purchased the car the original owner had an extra instrument cluster included with the car.  How can I test if the odometer on the extra instrument cluster works without attaching it to the car?  Not sure how hard it is to take out the instrument cluster and replacing with the other one to test out.

 

 

Thanks,

 

 

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any drill should spin it fast enough for the needle to move. did you try forward and reverse?  was the center drive cable confirmed to be all  the way into the back of the speedo?

 

did the speedo needle move and not the odo?

 

whether it works or not, i would send it to north hollywood speedometer.  they rehab those things and it comes back looking and working like new.  they can even recalibrate them to your specific tire/diff combo.  not that expensive.

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So I just tried with a drill and it spins but nothing is happening with the odometer.  Not sure if my drill bit is fast enough to really do the trick.

 

Drill must turn in reverse direction to turn the odometer, speedometer, etc. -KB

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Testing your odometer:

 

1. take a short piece (1-2") of soft aluminum or copper wire (6-8 gauge--I used a scrap piece of aluminum wire that's used to attach a chainlink fence to its post) and file one end square so it'll fit in the square drive socket on your speedometer.

 

2. Chuck the un-filed end of the wire in your power drill and fit the square end into the speedo drive. 

 

3. Run the drill in reverse and watch the speedometer; it should move up to 25-30 mph or more depending on drill speed.  The odometer number drums should also move. 

 

If they don't, take the cover off the speedometer unit and try it again, this time observing the little gears that drive the odometer number drums.  If the gears aren't turning, you probably have a gear that's come loose from it's shaft due to wear or cracking.  If it's cracked, go to Odometergears.com; they have replacement gears for sale with very detailed instructions for installation.  If the gear is merely loose on its shaft, check archives on how to deform the shaft so the gear is firmly attached. 

 

Good luck, and happy tinkering

mike

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whether it works or not, i would send it to north hollywood speedometer.  they rehab those things and it comes back looking and working like new.  they can even recalibrate them to your specific tire/diff combo.  not that expensive.

 

Interesting to note what they sent me regarding the calibration:

 

The average repair and recalibration of a 1973 BMW 2002 speedometer sells for app. $ 160.00 - 200.00 plus shipping depending on the extent of the damage. 1 year warranty. App. 3 weeks turnaround time.
To accurately recalibrate the speed portion of your speedometer we suggest to perform a ratio before sending the instrument for service. Please measure 52' 9 1/2" ( 1/100th mile ) slowly drive the car over this distance counting the speedometer cable rotations including fractions. This is a very accurate way to determine your car's ratio. Attaching a paper clip or tape to the end of the cable does help.

 

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that process is what i did when I sent my speedo to them for overhaul.               ez to do.  there is a cal sheet on their website that describes the process.  you fill it in and send it with the speedo.

 

unlike modern speedos that read off the diff, 02 speedos are only accurate if calibrated to the rotations of the cable per a given distance.  the measurement they describe takes into account your diff ratio and the diameter of your tires.  for this reason you need to do the measurement with the diff and tires you intend to use.

Edited by mlytle
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  • 2 years later...

what happened to the calculator on North Hollywood Speedometer website?  I think it was based on traveling a known fixed distance (1/100 of a mile?) and counting speedo cable revolutions.  Their website (nhspeedometer.com) home page is very bare-bones right now with no useful links...I see no link to any calculator sheet

 

I'm on the verge of having to have a broken odometer fixed by them and thought it would be a good time to have the speedometer properly calibrated.  Alternatively, I could tell them the tire size and differential ratio, but since I just bought the car, I don't really know what the differential ratio is.

 

Or should I just compare the existing speedometer reading to an iPhone GPS reading to decide if the speedometer really needs recalibration at all?

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