Speedo problem

[Bo]

I'm having trouble getting my new speedo working, could someone pls help me ?
The setup I have is:

1982 915 gearbox (and 930/10 engine)
1985 Speedo (July 1985, if that makes a difference)

So - I have a 3.2 Speedo for an SC gearbox - is that a problem? In my book it shouldn't be, but I could be wrong (it has happened before ).
The speedo get's power - I have checked that already - and the sender cable is attached properly all the way to the tranny - BUT, before ordering a new sender I just want to make sure the speedo is indeed compatible with the 915.

Anyone?

[Bo]

BumpiŽn up, since you american guys finally are awake

[Formerly Steve Wilkinson]

I had endless problems getting my speedometer to work after a total resto, and ultimately the problem turned out to be that I had the sensor mounted backward against the transmission. You'd think the "potted" side would go next to the tranny, but it's the other way around: the potted side faces out. Check that first. If that's not it, I'll give you some more hints on confirming sensor continuity, etc.

Stephan

[Early_S_Man]

Bo,

The sensor is a simple magnetic reed switch, which is triggered by eight magnets on the ring gear assembly. If you put the car up on stands ... and connect any kind of multimeter to the two leads that go to the speedo. Have an assistant slowly turn the right rear wheel over while the transaxle is in neutral ... while you are watching the multimrter for contact closures (resistance close to zero) ... eight closures and openings should occur during one revolution of the rear wheel! If you don't get those closures at the speedo connections, then move the multimeter to the short white pigtail leads coming out of the sensor, and repeat the test! If you don't get the contact closures at the sensor leads ... either the sensor is reversed/backwards in the housing or defective!

[Bo]

I just took the car for a spin around the block, with a multimeter connected to the sender cable, in Hz mode, trying to detect the pulses - nothing registered at all!
Seems like all evidense points to a faulty sender, doesn't
it?
The sender hasn't been out of the tranny since new (that was suggested in one reply), so that can't be the problem.

Looking in parts catalogs, I noticed that speedos range from year 74-89, while 915-senders go from 74-84 AND 85-86 - that means that I should buy a 74-84 sender, even though the speedo is a later model, right? (my tranny is an 82)

Just want to get this right, so I finally can get the speedo working.
That way I can tell exactly HOW much faster than legal I go .

[Early_S_Man]

Bo,

The sender doesn't generate any signal by itself, just like points! So, if you want to repeat the test ... connect a 9 Volt battery, and a 1000 Ohm resistor to the sensor leads, and connect the multimeter across the resistor.

I think there is some confusion about sensors and 915's! The '76 model was the first to use the sensor and electronic speedo! Obviously, you want a sensor for an '82 915, and it won't make any difference to your speedo!