Recently I noticed that the temperature LED display is missing some LED segments. The segments that don't work form a vertical column such that 59 looks like 53.

The picture of the LED display is shown here:
How should I repair this?

 

Here is the picture of the temperature LED display: http://www.flickr.com/photos/54230006@N07/5237007316/

 

Yikes - that's not good - I take it you are out of warranty period?

 

You probably have to replace the entire LED cluster (or a good chunk of it). There might be an easier way, but if it's anything like the LED cluster on BMWs you will likely have to toss your current one and find another in good working order. If it doesn't bother you that much, I wouldn't bother IMO.

 

Is the Outside air temp readout that is with the HVAC settings(upper, center console) working fine? If so, I am with CarGuy. Just use that one.

 

Yes, the temperature display above the HVAC is working fine. I concur that the LED cluster must be going bad... must it be fixed by dealer?

 

The fix is probably too complex for the dealer - they would replace the whole thing. However, if you want to attempt fixing it, here are some ideas:

A common cause of vertical line failure on LCD screens is called a TAB (tape automated bonding) Fault - a bad connection in the ribbon cables connecting the circuit board(s) and/or IC chip(s) to the actual LCD panel.

If an LCD display is subjected to extreme heat or cold or physical shock, this could cause one or more TAB connections to fail inside the display. This failure is often caused by horizontally flexing the panel or simple failure of the adhesive holding the TAB against the glass. If these connections were to fail, the effect would be that an entire row or column of pixels would fail to activate. This causes a horizontal or vertical black line to appear on the display while the rest of the display would appear normal. The horizontal failure runs from edge to edge; the vertical failure runs from top to bottom.

If this is the problem, it could be fixed by reseating all of the ribbon cable connections. Start with the ribbon cables that have the most amount of flex since these will likely be the first to fail (ie. cables bent into a U shape).

The ribbon cables may be epoxied onto the circuit board or IC chip. If this is the case, you'll have to figure out a way to remove the bonding without damaging other components. A 1mm precision soldering tip could help you remove it, or use a heat gun on the general area to reseat the connector in-place without removing it.

Another cause could be that the resistor supplying the driver chip is bad. I haven't seen the inside of the LS430 combination meter but on LCD/plasma TVs, there is a chip for each line (or group of lines), and a surface-mounted resistor for each chip. These chips are soldered onto the ribbon cable on an aluminum plate. Over time, the resistor can fail (possibly due to thermal stress). If you have the whole thing taken apart, I would resolder all resistors and capacitors in the general area.

Another cause could be a failed connection at the back of the LCD glass surface. There are several methods used to make the electrical connection to the glass surface. One that is easiest to repair is the one that uses a conductive rubber-like strip sandwiched between the display driver part of the PCB and the LCD's rear glass surface. For some reason, the actual electrical resistance between this rubber-like strip and the glass becomes too high. It is quite often corrected by a simple cleaning of the glass, rubber-like strip and the PCB lands that the strip touches. Use a Q-Tip slightly moistened with 90-99% alcohol.

The above is only useful if you are able to disassemble the LCD's mounting assembly and put it back together successfully. Manufacturers have not made this easy in most cases.

Less likely causes are that the LCD driver chip is bad, or each of those little LCD segments are bad, or the car experienced a power surge and something impossible to pinpoint was damaged. These require total replacement of the cluster.