Speedo Troubles . . .

[Ronnie's.930]

Hello - my speedometer (electronic version on a 1987 930) has not worked since I overhauled the engine and transmission (it worked fine prior) . . . I tried replacing the speed sensor on the trans and still no workie . . . any ideas/words of wisdom ???

Thank you - Ronnie

[s_morrison57]

Ronnie
Mine is the same , I don't have the Ca Joe Knees to do a rebuild ---- yet but some times my speedo works and some times it doesn't. I'm thinking lose wire but 101 Projects freaked me when it said the wires may be short - be carefull , so I'm thinking how the "H" did they get it in there if the wires were to short? Who knows what happened in "Da Fadder land" 21 years ago. Is the guy who hooked it up still alive????
FSM

[lucittm]

Send it to North Hollywood Speedometer, it needs to be checked, cleaned, and calibrated at a minimum anyway.

Mark

[Ronnie's.930]

Does anyone know what the speed sensor "reads" (what is spinning withing the trans that the sensor is picking up) ???

Ronnie

[zcoker]

You know, mine had done the same thing, just stopped. Then someone told me to check the clear plastic double connector under the shifter coupler plate between the seats. I kind of blew that off, checking all other things and then started looking for another speedo. Then one day I decided, what the hell, so I took off the cover and the plastic connector seemed fine but upon closer observation, I could see that one of the spades was a little out. It's hard to see. So I pushed it back in and, bingo, speedo came to life and works great. The shifter coupler moves it around in there, so it needs to be tucked and tied up good. Go figure.

[spuggy]

Originally Posted by Ronnie's.930

Does anyone know what the speed sensor "reads" (what is spinning withing the trans that the sensor is picking up) ???

Ronnie

It's a Hall Effect sensor. There's a few magnets in the box, as they move past the pickup (a simple coil, I'd presume), EMF is first induced as the magnet approaches and then collapses as it moves away, generating square wave pulses which are counted by the speedo head.

Speed/distance is then displayed based on the distance covered in a complete wheel/tire revolution - on the sizes of wheels/tires selected at the factory...

[Ronnie's.930]

Thanks for the info and suggestions! The new sensor included new female connectors and such so I don't think I have a wiring issues (though I will double check this, of course) . . . pretty confusing as it worked fine prior to the engine and trans rebuild . . . I wish I had some way to check if the sensor was picking-up a signal from the trans . . .

Ronnie

[mark houghton]

Originally Posted by Ronnie's.930

I wish I had some way to check if the sensor was picking-up a signal from the trans . . .

Ronnie

Since a small pulsed voltage is probably generated each time the magnet passes by (inducing a voltage into the coils of the sensor) a person might be able to mesure the output with a millivolt meter. Disconnect it at the coupler under the shifter coupler cover plate, and connect your voltmeter in place. Drive the car and see if you get a reading. Or, maybe check the continuity of the sensor itself (with an ohm meter). Anything more than a few ohms resistance probably means a bad sensor.
All conjecture, of course, but logic tells me this might be worth a try. I can't imagine the sensor itself going bad unless physically damaged. You may just have a break in the wire(s). Pull the whole damn unit out of there and take a look! Oh...and good luck!

[Ronnie's.930]

Thanks for all the help . . . as it turns out, I had the sensor mounted "backwards" (the wrong side of it facing the trans) . . . nice, "booba-the-foo" move on my part !!!! Oh well, live and learn, and I'm just glad that everything now works and that I only needlessly bought one part (not the first, and won't be the last time for that) !!!!

Ronnie

[mark houghton]

Originally Posted by Ronnie's.930

Thanks for all the help . . . as it turns out, I had the sensor mounted "backwards" (the wrong side of it facing the trans) . . . nice, "booba-the-foo" move on my part !!!! Oh well, live and learn, and I'm just glad that everything now works and that I only needlessly bought one part (not the first, and won't be the last time for that) !!!!

Ronnie

Jeeze!! Ya know, I thought to mention that as a possibiity...only because when I took my engine out last year I had the same doubts on whether I put the sensor in with the correct side facing. I figured I had a 50/50 chance of it being right, or that it wouldn't matter either way. You just confirmed that I was lucky after all!!!

[infraredcalvin]

Ok, now that that original poster's issue has been resolved, I can hijack. I have speedo issues as well, seems to work fine until the needle hits 55, then just stays at 55 (i think she's trying to tell me something) just started doing that, worked fine before. Anyone else have this same issue?

Thanks in advance...