Speedometer Help Needed

[medarwin]

Have a dead speedo in my 82 SC. Initially, I cleaned the mounting location for the sensor puck. No luck. Figured it was the speedo so sent it to a shop for a re-build. Turns out the speedo is fine, works great on the bench. Figuring that the only possible remaining cause would be the sensor itself, I just installed a new one today.

Speedo/odometer dead, nothing. Have polished connections in tunnel, out of ideas. Lights in housing work so I am ruling out a bad ground.

Can't put the care on the road until I get this fixed as I cannot get an inspection sticker without it. I've read all the threads I could find on this problem but still not coming up with an answer. Help? Anyone? Anyone?
Thx, Darwin

[zedsn]

There are threads on Pelican I believe of magnets becoming unglued inside of the transaxle causing a no work speedo.

[timmy2]

Most recent thread ended after the OP discovered he put his new sensor in upside down.

[medarwin]

Not sure if it can be put in wrong (the sensor), you have to line up the wire in the slot...

I don't have an analog multimeter, just digital. Can I test it with the digi or do I need to buy an analog?

thx,. Darwin

[petercory]

The capicators and diodes go bad in these Speedos, time to send it to North Hollywood Speedometer for a rebuild, this is not a DIY!!!!

[medarwin]

Sent it to a Speedo shop in MI that does restorative work/rebuilds. hey said it was fine, no problems.

[brianlay]

It's easy to check the sensor.
It's just a switch that closes when near a magnet.
Connect a continuity tester across the wires to the sensor at the connector in the tunnel. Your DVM will work, it's even better if it has a beep setting. Raise the right rear wheel, and with transmission in neutral, rotate the wheel. You should get 8 closures (or beeps)per revolution. If not take a closer look at the sensor installation. Maybe pull it out and try a magnet near it. Make sure it's rated correctly...there is a front and back side
If the sensor is working check that you have +12V and ground at the speedo.
You didn't mention when you last saw it work...what changed since then?

[medarwin]

Brian,

Thanks, I will check with DVM. The car had some serious fuel issues (see my ancient posts) which caused it to be relegated to the barn until I figured it out. So, when I got it out and started to seriously work on it and got it fixed, the speedo wouldn't work. If the magnets ran away (I understand there are 8?) I doubt they would all go on vacation together. So even if I just had one hanging on, I would get intermittent pulse to the speedo which SHOULD cause the needle to flutter, jump, something.

Rated or installed correctly? I don't think it is possible to install it wrong but I learn new things each day.

Which wire should I check for 12v at the speedo? Your help is greatly appreciated. Thanks, Darwin

[island911]

Test the sensor by turning the RR wheel with the meter checking for continuity. If you are getting the on/off pulses, the sensor is good.

Next up, check further along the wire. Behind the seats, there's the access to the tunnel. The speedo has a connector there (often tucked up along the upper right side). Put your Ohm meter there and turn the RR wheel again. Then you'll know if the break is fwd, or behind that point. (likely behind)

Chase down the wire, looking for breaks.

[mattchanin]

Hey folks, I'm getting only 3 pulses when I rotate the rear wheel 360 degrees (1981 911 SC). Does this mean the magnets fell off? What's the fix? Pull the tranny and replace? TIA.