The fault of the LCD was that it only displayed a couple lines of output on the LCD. The symptoms are caused by poor location of the LCD ribbon in manufacture and also the poor position of the whole module in the vehicle which exposes it to heat and is subject to vibration within the vehicle. This causes the ribbon to fail eventually and is a known common fault.
The ribbon in this display actually controls the Rows of the LCD matrix and the Columns were handled by a rubber standoff connection on the longest side of the LCD. There were no problems with the rubberized connection.
Some re-work on the LCD ribbon had already been tried with a little improvement but the poor registration of the ribbon pushed me to try a new attachment.
From the photos below you can see the LCD control unit and the state of the LCD ribbon before repair. You can just make out the offset placement and poor registration of the ribbon before repair.
The marks on the ribbon are my mistake of applying too much heat during re-work attempt (see my tips for applying heat and lessons learned later).
Do not under estimate the patience required for this repair as some delicate and nimble work is required and i cannot stress how important it is to take your time and not rush. You may only get one chance with this sort of repair.
The registrations of the LCD ribbon in this repair was difficult. It took me and my friend 20 minutes just to line up the ribbon for re-attachment. The ribbon in this case is sub 1mm pitch OR less than 25.4 thousands of an inch. You may want to try a simpler ribbon repair on an old LCD clock for example before jumping in head first with fine pitch.
Also the removal of the LCD ribbon is a delicate process as you do not want to tear what is a good ribbon or damage the carbon printed lines. Also the PCB must be respected to avoid introducing other faults and the the re-attachment may need an extra pair of hands.
You may also want to review the last step for results and lessons learned from this instructable before jumping in head first but i believe this will give a you a good insight to some important factors of LCD ribbons and possible success.
1. Eyepiece - X10 minimum, X20 Preferred - For Viewing/Cleaning PCB pads and registration of ribbon
2. Scalpel with rounded blades - For ribbon removal and trimming.
3. Small Ruler - plastic or metal - For trimming and clamping of LCD ribbon
4. Solder Iron Or Hot glue gun - For applying heat, adjustable temperature solder iron would be preferred.
5. Small amount of Tinfoil - For wrapping over solder iron or glue gun nozzle
6. Cotton Wool Ear Buds - For cleaning PCB pads
7. Isopropanol Or Methylated Spirit - For cleaning PCB pads
8. Another pair of steady hands - For clamping the LCD ribbon in place
9. Tweezers - For removing leftover ribbon.
If you don't have X10 eyepiece to hand but you have an old scrap scanner you can pinch the lens out of it. The lens is close to X10 conversion.
Step 1: Before you start, make an assessment of LCD Ribbon and Module
So Before you start:
Have you tried reworking ribbon? There are already some good techniques for small repairs such as the hot air gun technique.
Other favorites of reworking the LCD connection that i have read here are the tinfoil on a heat gun. This has good temperature management but not so good in tight spaces. The solder iron with flat blade and tin foil is more precise but a 25 Watt iron can be too brutal on the ribbon.
If you have tried re-working the ribbon with no more improvement then these are my next steps of LCD assessment.
1. Do you have enough spare ribbon to detach and re-attach? The more ribbon you have the more goes you may get but watch out for the mechanical caveat below.
2. Will you be mechanically constrained if you cut the ribbon. This is a tough one as some shortening of the ribbon may make it impossible to re-assemble the device!!
3. Is the Ribbon continuity visibly good, by that i mean the carbon connection lines are continuous and unbroken - Do check otherwise you may be wasting your time.
4. Is it really the ribbon causing the problem? The driver chip could be failing.
5. Finally the easiest call is made by the item is going to be trash and you got nothing to lose.
In the photos below you can see the available ribbon length was generous enough but do watch for mechanical constraints. In some cases you could find yourself not being able to lay down the LCD back down as it is too tight a radius to sit down.
The photo with the pencil pointing indicates how much ribbon was available.