jwillman

Still looking for any advise or recommendations. This weekend I will raise the back end and try some voltage measurements with the wheels rotating.

At this point I don't know what to suspect and without a spare speedo I can't swap and test. What year speedometers from other Porsches, 928/944, are compatable?

jpitman2

Have you located the point at which the 12V goes downhill? Try shorting/bypassing the diff sensor connection at the spare wheel well connector. If that gives 12V back the CE board, the sensor is a high resistance, but that would surprise me.
jp 83 Euro S AT 54k

jwillman

As I understanfd the system from what Wallyp provided the system voltage starts at the gauge. I have power into the gauge but only ~5v coming out going down to the H1 on the CE panel. I will jack up tomorrow and rotate the wheels to see if I get a different voltage reading.

jpitman2

I may have missed something, but are you saying that you have +12V going into the speedo head, and only +5V coming out ? Both mesured against the same ground? That would tend to say the gauge is done for. Have you checked your new connection at the gauge input pin/bolt/whatever? Whatever you last changed has got to be the prime suspect.
jp 83 Euro S AT 54k

jwillman

Absolutely agree with the last change suspect. I pulled the fiber board pin connector off the shot circuit sheet and soldered the hardwire to that board to get the ground, power and signal into the gauge. All three have continuity. Overseas Speedometer is in Austin. I have sent them an email about testing the speedometer.

It worked before I started the odo gear and hardwire project. Not sure what I might have done during the odo gear change to cause this as ot mess with the electrical side of the gauge at all.

jwillman

It did indeed turn out to be something I did or rather did not do

I did some more wiring checks on the pod and still had good continuity but only half the voltage on the signal wire. I disconnected the ground wire at the gauge and presto had system voltage on the signal wire. That confirmed to me that it was not the gauge but rather my wiring.

I went back to the wirng diagram and I realized I had missed a ground jumper from pin 7R to 11R on the car side during my hardwire modification. 11R is a ground wire that runs to pin H2 at the CE panel which is in the speedo circuit. I installed the ground wire and now have operational speedometer and odometer to boot for the first time since I owned the car.

Speedometer is reading 60MPH when GPS shows 58MPH but I am tempted to leave it alone. My luck I would snap the speedo shaft trying to get the 2 MPH!!

Now to reassemble the pod and get on to the next project.

Thanks all for the input and yet another validation of the old saying check where you last worked!!

Kalspeed

Good troubleshooting!!!

SMTCapeCod

and good on ya for posting the solution...too many threads trail off with no solution-- especially when there's some culpability for the fault...

jpitman2

similar to my problem when doing the pod - after reassembly I got a pegged fuel gauge on sidelights - probing the connectors had bent the ground connection on one of the R pins, and the only grpound available was through the fuel gauge...
Glad you found it. Thats a lot of work you put into rewiring the pod, and if this is your only issue, you should be very pleased.
jp 83 Euro S AT 54k

pcar928fan

YOU ARE THE MAN Jim Willman!!! Way to go bro!

Thanks for getting the battery out of the '92 yesterday! Elliott put the new battery back in and I drove it for the first time in awhile today! That car is SOOO NICE! I really miss it when I don't drive it!