There are two versions of the magnet carrier disc. One is for the G50.00, G50.01, G50.02 with open diff and the other version is for the same three plus the G50.50 ('89 930) with LSD. Regardless of type, the carrier disc is the same layout in terms of magnet count and location on the disc.

The one pictured is a LSD. I have seen a non-LSD carrier disc from my own '87 and my recollection from memory is they are nearly identical looking

88911coupe,

Check out this thread. I had a similar situation with the 4 magnets and undersized (loose fitting) sender cable. My comments start about halfway down the thread. I can't explain it but I have had no problems since I changed cables.

http://forums.pelicanparts.com/porsche-911-technical-forum/442139-speedometer-casis-cruise-problem.html

Cashman, thx this may be my solution. What was the part # from the dealer? I noticed the new one is slightly different than the old one and it does not fit snugly in the tranny hole.

#911-606-910-01 is the part number and it has been installed for 1 1/2 years and has worked ever since. I will be curious to know if it solves your problem as well. Like I said, I can't explain why the other (2) cables didn't work but this one did. Maybe third times a charm! Good luck.

OK...figurered it out with Cashman's most excellent help. If I put the "new" sensor in about halfway into the hole and rotate the wheel I get 4, yes 4 distinct beeps on the VM set to continuity...not eight. This might explain (I think) a couple of things.
1. This "version" sensor, as designed, does not work well with the 4 magnet wheel...it's too far away. Maybe version is wrong word...
4. Why I just get a weak (approx) 40 mph reading when I'm actually going 75-80.
The obvious question is how the heck do I get one that works with my wheel.
Thanks, at least I know what the problem is.
BTW, that's the part # I ordered from Pelican. I guess I'll try to exchange it.

Wrap up for the benefit of anyone else who may have to go through this complete PITA. After a lengthy talk with the parts guy at Autoscope here in Dallas we determined there is only one valid part # for this that is for the G50, however, I DO have a 4 magnet set up in my tranny, as did Cashman I think. I was told by one of the highly respected speedo guys (honestly trying to be helpful) that all are 8 magnets and if I am missing any magnets they fell off or something. In fact, there appear to be some with FOUR magnets. Note that this is not really an issue since my speedo is apparently set up to work with 4 magnets. The bigger problem others may run into is that the newer version of the sensor won't pick up the magnet "signal" UNLESS the sensor is only inserted about halfway into the tranny. Cashman returned one or two and maybe got lucky when he picked one up from a Porche dealer and, thankfully, his worked. I have no idea if it would only take me 2 or 3 tries to get one that worked so I fabricated a way to keep the sensor from inserting all the way into the hole with a piece of heater tube. Now it's registering the magnets fine but it's in now way a perfect solution...very kluge but I don't have any choice.
Just wanted to offer this suggestion in the event some other Pelican gets stuck in this situation. No way this should have dragged on for three weeks!

Thanks for the update. That gives me a little more confidence in my conclusion that I only had 4 magnets? For what it's worth the third cable I got from the dealer (with the same part) was definitely different from the previous (2). It was the same size diameter as the original (not smaller and loose fitting as we both indicated) and I believe the o-ring color matched the original (Green I think) where the previous replacement cables both were black. They may have had the same part number but they came from different factories/sources. Thanks again for the udate.

In my talks with the guy at autoscope he could not tell for sure if there was more than one manufacturer but I know there has to be. I just dont know a way to specify so I'll have to make due with my homemade solution

For future reference, if someone wanted to replace the speedo magnet ring? It's really not hard at all to remove the differential.

-Disconnect CV joints at transaxle drive flanges
-Remove drive flanges via center screw
-Remove transaxle side cover (takes a bit of fiddling to get the o-ring to release the cover from the final drive housing)
-Differential can now be lifted out of the housing.

Speedo ring is held on with just some simple spring clips. Swap in your new speedo ring and diff installation is the reverse of removal, as they say in the service manuals.

Help needed.
 

One morning, my speedo didn't register at all. After in town driving for 10-15 minutes I got out on the interstate doing 70-75 mph (used tach) for about 15 minutes and it suddenly popped up to the correct speed reading and worked fine: rock steady at all speeds even when I came to a stop. When I came out 2 hours later it still worked fine. :confused:
-I didn't drive it for a week and the same thing happened. Didn't work, highway, worked the rest of the day (even after stopping for a few hours).
-About 3 days later I cleaned the magnets and the sensor as suggested in another thread. After cleaning, I drove it and I had the same problem: pop up and work perfectly after 15 minutes on the interstate.
-Two days after that I got in it and it worked fine from the get-go.
-Two more days later: no reading. :mad: I drove it 35-55 MPH for 35 minutes. No joy. Parked it for 2 hours and then took it onto the interstate. 15 minutes later it pops up and works fine! I'm seeing a pattern so after getting it to work, I park it and immediately jack it up and put a meter on the wires in the tunnel. Continuity goes from 1 to almost 0 eight times per revolution. The sensor seems to be working fine.

What do I try next? I really don't want to buy a sensor if I don't need one (especially when some folks have had problems with the replacements and they had to buy 2-3 to get one to work).

Monday morning bump. Any ideas?

I think what was wrong with my original was that the sensor wire was broken somewhere and made sporadic connections.

"I'm seeing a pattern so after getting it to work, I park it and immediately jack it up and put a meter on the wires in the tunnel. Continuity goes from 1 to almost 0 eight times per revolution. The sensor seems to be working fine."


It should read accurately if you tested it while it was working as mentioned above. Try testing after it sat a day or two. My guess is you will receive no readings. That was my experience. Once the car warmed up a couple miles, it would work.
Mark

Cashman: I was planning to do that. Here's what I found:
After sitting 24 hours I tested it Monday afternoon. Readings were perfect.
Early Tuesday Morning: Continuity read a constant 0.05 without changing (the wheel was a little harder to turn but I guess that is just cold trans fluid).

Can it be anything other than a stuck sensor?

http://forums.pelicanparts.com/uploa...1318946320.jpg

http://forums.pelicanparts.com/uploa...1318946730.jpg

^ Another option for those who want to upgrade to modern times... a speedo that is hassle free with a lifetime warranty. As shown above installed on one of my Type 2's.

GPS speedo custom made to my specs by SpeedHut.

Takes less than 1 hour to install if that and is super light. It keeps your maximum speed, your real time direction (North, South, etc), your 0-60 mph time, your 1/4 mile time (exapmple; come to a complete stop, set the button to 1/4 mile, as soon as your car moves the timer starts....it gives you your time at the end of your run).

$315 shipped.

This speedo has NOTHING to do with the transmission. It's all done by SATELLITE.

You can choose from a variety of colors, sizes, number styles, kmh or mph, lighting ect. All info on their website.

GPS Speedometers Gauge, Revolution Gauges Series by SpeedHut

They have excellent customer service.

.

Thanks AA but I'm sticking with the stock look.

If it reads a constant number while turning the contact is either permanently opened or permanently closed. I believe that is your problem. Once warmed up it will operate correctly. Here is a picture of my sensor. I had to cut it open to see what I could figure out. The switch is within the glass bubble. I believe it is a mechanical connection. Once it is magnetized the switch closes and that is what provides the continuity. Off magnet, switch is open. The switch is so small I cannot see it actuate if this is in- deed how it works. Someone smarter than I am will have to elaborate if this is not how it works. Your symptoms are exactly as mine and I have not had a problem since I installed the new cable.



http://forums.pelicanparts.com/uploa...1318978359.jpg

I have exactly the same problem that Por_sha911 : not reading when cold and after 10/15 minutes driving, OK. When stopping 3/4 hours, not problem; when stopping a week, not reading.

So, is the solution to change the sensor?

Wanted to chime in here as well.. My car has this exact same problem. Let it sit for a day and neither the speedometer or odometer works but after 15-20 minutes of driving, it works flawlessly.

Subscribed.

I started this thread about two and a half years ago. The speedometer has worked flawlessly and the problem has never returned.