Resurrecting a dead speedometer?

[green71]

My speedometer died this weekend. Previously, when it "worked," the needle would bounce between 0 and about 30 for several bounces, and would then level out to correct readings at above 30mph. This weekend, though, it began by springing between 0 and whatever speed the car was going, never leveling out to a consistent correct speed. It finally come to rest at 0. Can't coax any reading out of it now.

I suspect that only three things can go wrong with a speedometer: the speedometer drive shaft, the speedometer cable, and the gauge itself. Naturally, I'd prefer not to systematically replace each piece only to find out that the third & final piece I've replaced is the culprit. Any suggestions?

Thanks,

Mark

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1971 1.7l 914
Willow Green

[campbellcj]

I just went thru this myself. First you need to determine which part(s) is/are at fault. It is most likely the cable or the angle drive, as the speedo portion of the VDO gauges seem very reliable.

You can test the cable & gauge by removing it at the tranny end and spinning it with a hand drill or similar motor.

In my case it was the angle drive, which is a piece of cake to replace. I also had Palo Alto Speedometer rebuild my speedo anyway to fix the odo and tripmeter and clean everything: now it looks & works like new.

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Chris C.
73 914 2.0
70 911E Targa
campbell.chris@gte.net

[green71]

Chris,

Your troubleshooting technique sounds so simple yet effective that I would probably never have come up with it myself. Thanks for the great idea.

BTW, what did the gauge rebuild cost, if you don't mind me asking?

Thanks,

Mark

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1971 1.7l 914
Willow Green

[green71]

Chris/anyone,

Is the "hand drill" recommended for this procedure a power drill or a manual drill? I'm not sure how much speed/torque the cable/speedometer can handle and I'd prefer not to break something I'm trying to fix.

Thanks,

Mark

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1971 1.7l 914
Willow Green

[SteveStromberg]

I had North Hollywood Speedo fix my speedo it was $100. Steve

[campbellcj]

Yup, it costs between $80-120 to have speedos rebuilt, depending who does it and what is wrong with the gauge.

Honestly, I never had to spin mine with the drill to test it, because the instant I pulled out my angle drive I could tell it was the culprit. It is supposed to "engage" with the tranny and not spin freely in both directions. Mine felt "floppy" and spun with no resistance in both directions.

On the drill technique, I would either use a hand drill, or a variable speed electric drill on a slow speed to start. You don't want to run the thing 4000 rpm's...just enough to get movement out of the gauge.

[HMeeder]

I have rebuilt my speedo myself using the Tech Article and had great success. Be [b]very[b/] careful when prying off the trim ring. It is quite possible to crack the ring or chip the glass by being over-zealous. Be patient and methodical.

Also, used a standard cordless hand drill and had no problems. It really is the easiest way to bench test the speedo/odo.

Good luck!

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Herb
'72 1.7 Tangerine 'Teen
'74 2.0 Red Rustmobile

[green71]

Well, I propelled the speedometer cable w/a variable speed drill & still no reading. This weekend I'll try removing the cable from the gauge and do the same thing to see if the cable's spinning at the gauge end. I'll try it with a little tension on the cable at the gauge end. If there's still no reading, that should pretty much point to the gauge!

Thanks for the help,

Mark