Update: FTE removed all the old albums so the photos below are no longer available.
Subford made a PDF file of them and link is in post#10

My 95 E350 Bus PSOM started to act up due to the capacitor
leaking acid onto the PCB. I fixed that(so I though) After 2
years I noticed my MPG was dropping almost to 1MPG!! Short story
I found the PSOM was not saving the milage into the EEPROM when I
turned off the ignition. It would only save the data every so
often. No wonder why the MPG went south!

As I had 3 extra PSOM's I decided to experiment with them.. . So
I unsoldered the EEPROMS and installed 8pin sockets on to the
PCB's. I found I can swap the EEPROM's between the PC boards
without any issues!! Thats good as I can put my PSOM EEPROM onto
a good PSOM circut board and keep the milage and the most
inportant PSOM RATIO programing.


The first two had fogged up ODO displays and the 3rd one is good,
I wondered if I could clean them up.

The first PSOM I took totaly apart and here's what inside a PSOM:

You can see the ODO display is messed up and had a film scratch
peeling up:

Using a razor blade I was able to pull off that messed up film
from the ODO:

Unfortanitly this LCD display is bad as you can see the dark
blotches running twards the center of the LCD display. No fix for
that besides replacing it.
Anyway I put it back together and you can see the diffrence

I used that one as a test pig to see what could be done, but with
the ODO LCD display bad its junk....On to the 2nd PSOM.
This time I took more phots of the steps I did and also done it
with out removing the needle! Here's the before look:

After removing the PSOM circut board this is what you see:

Remove the 2 screws that hold the white light bar down and ONLY
LOOSEN the 2 screws that hold the meter in place. This way you
will not have to mess the the speedo needle.
Now carefully pull the light bar down and out:

Now you will see the ODO display. The two I did, it was just
laying there being held inplace by the light bar. Be carefull
with the white ribbon cable, you dammage that or the display, its
game over.

Now with the ODO display out I used the light bar to support it
and used the razor blade to carefully get a corner of the film
lifted to pull it off.


Reassemble the PSOM in reverse order and this is how this one
looks:

ON the 1st PSOM I think someone tried to clean the ODO display
and hence scratched the screen. That told me it could be removed
and help clear up the cloudy ODO display. That film was
installed to help protect the display from scratches. As the
instrement cluster is a sealed part(unless the lens is cracked) I
doubt the lack of that film will cause any issues.

Now onto figuring out the EEPROM data and maybe reprograming them....

 

Found the EEPROM is a Microwire 93Cxx or 93LCxx varient. Now to figure out how the data is stored on the EEPROM.

 

Update: I have found some odo displays had only one film on it, not two like in the above photos. That 2nd film(directly attached to glass) is a polarizer film to make the LDC work. Removing that will cause a blank odo screen. The 1st film is a protector to the polarizer film

I found this out the hard way after I peeled it off.

You can replace that polarizer film from another web site said(forgot which site). I have not tried that yet
Here are some examples of polerizer films :
Not sure which will work the best.


As for the EEPROM. It is a 93C06 EEPROM. I have figured out how the PSOM saves data and are able to reset the lock down count back to 6. As for the mileage, its encoded and I have not figured that out yet.

Interesting notes:
The PSOM saves mileage down to the .01 miles but only shows the .1 on display.
The speed output of PSOM is 8000 pulse per mile. It is a square wave at 50% duty cycle and is true AC wave form at 12V peak to peak.
(the 8000 ppm is also same as Chrysler digital dash speedo of the mid 80's, I use my old Caravelle's digital speedo to verify MPH output)
Frequency varies up to 120Hz.(under normal driving) Some PSOMs are able to output a 440~HZ which is a calculated 200MPH
There are some speedo meter adjustments stored in the EEPROM for low scale and high scale meter settings(have not fully figured it out yet)

PSOM speed output goes to the ECU and speed(cruse) control. Loss of this signal means the E4OD automatic transmission will shift bad and speed control will not hold speed or even set.


Here's a project related to this with more photos: https://www.ford-trucks.com/forums/1...r-display.html

 

How are you reading the EEPROM?

 

I unsolder the EEPROM off the PCB and use a program called "Ponyprog" too read/write. Others have used a "clip on the IC reader" to attach to the IC and other programs.

I have not tried the 2nd way yet, I recall the link above will talk more about it.

 

 

I cant see the pics either.

 

Are you able to write to the EEPROM?

 

FTE did a software change and I lost all the old albums I had, wished they would of told us so I could of made backups of the photos.


On the EEPROM, I can read and write to it as it is a common Microwire 93C06 EEPROM and there are many EEPROM programmers out there. All the data stored on the EEPROM is encoded so its not easy to put any data back in as the PSOM will error out. Ford did a good job on the encoding and so far I have not figured it out.

The way I reset the lockout was to read a PSOM that still had 6 left and copied that EEPROM location over to my PSOM EEPROM and that worked. As there are no information on where and what was stored on the EEPROM, I had to brute force read/write locations to figure things out. That took alot of time.

 

The missing photos are in the attached PDF.

 

Right on Subford!! Good to have them photos back. I edited the first post with your PDF link.

 

Can you pm me Eddiec1564

 

Can't send a PM as your a new user. Whats your question?