Pod Removal and Troubleshooting (on an '85 928)
The gauge package
One of the things that I did while I had
my gauge package out was clean up all the contacts. I had a
problem with speedometer needle and tach needle sticking unless I
tapped the pod. When I got in there (thanks to a few hints on
Rennlist) I found that there are four rivets that are the only circuit
connection between the speedometer circuit board and the ribbon 'board'
that's on the back of the gauge package. In fact it's only after
I took these pics and posted them that I realized there is a
one-for-one connection between the 4 pins that stick through the
speedometer circuit board and the rivet connections. You can see
the faint horizontal solder traces in this first photo, but you can't
see them just by looking at them. The flash must have shown them
or something.
On my car and on others that have posted
on Rennlist, this set of connections is the cause of the speedometer
sticking. The circuits work like this:
The rivets connect the circuit you can see on the ribbon 'board' through to the solder traces on the underlying wafer board.
The traces on the wafer board (seen as faint horizontal lines leading left-to-right for the top three in the above picture and right to left in the bottom rivet) connect the circuit from the rivets to the pins that stick down into the housing, where they make contact with spring type metal components mounted on the speedometer proper.
The pins go through the speedometer board, making contact using only metal-to-metal spring tension.
As you can see, there are several weak points in just the small part of
the circuit that I've described.
The rivets connect the circuit you can see on the ribbon 'board' through to the solder traces on the underlying wafer board.
The traces on the wafer board (seen as faint horizontal lines leading left-to-right for the top three in the above picture and right to left in the bottom rivet) connect the circuit from the rivets to the pins that stick down into the housing, where they make contact with spring type metal components mounted on the speedometer proper.
The pins go through the speedometer board, making contact using only metal-to-metal spring tension.
Depending on your skill with a soldering
iron and your level of comfortable risk, you have several options:
Most would say: "Just clean up the contacts and pins and put it all back together." This will probably work.
Some would say: "What's with all this rubbing metal together to make a contact crap?" like I did and want to solder everything.
Some would say: "That's cool, but I'll just buy one that works and swap out my speedometer/odometer and be done with it." This is probably a good answer too.
I couldn't get a closed circuit between the end of the pins and the end of the circuit traces which you can follow to the plug connector in the right of the above picture, so I made wire jumpers and soldered them between the middle two rivets and the corresponding pins. This worked for me.
Hope this helps! Good luck!
Most would say: "Just clean up the contacts and pins and put it all back together." This will probably work.
Some would say: "What's with all this rubbing metal together to make a contact crap?" like I did and want to solder everything.
Some would say: "That's cool, but I'll just buy one that works and swap out my speedometer/odometer and be done with it." This is probably a good answer too.
I couldn't get a closed circuit between the end of the pins and the end of the circuit traces which you can follow to the plug connector in the right of the above picture, so I made wire jumpers and soldered them between the middle two rivets and the corresponding pins. This worked for me.
Hope this helps! Good luck!