Automobile Climate Control LCD Panel Fading

[hunsra]

Hello,

I'm trying to diagnose and repair a monochrome LCD panel in my car that fades when the outside temperature exceeds 90 degrees F.  The panel works as expected when the temperature is lower, but begins to fade as the temperature rises.  When hot enough, the panel is completely blank.  My question is: can this be caused by a failure of the power supply portion of the circuit?  Could some discrete component of the power supply circuit be affected by the heat and stop operating as expected, or is it more likely a connector or wiring component being affected by the heat?  Any thoughts or ideas are appreciated.

Thanks,
Randy

[SeanB]

Fading when hot could be the panel itself, the connections failing with thermal expansion, the controller running too hot or failing capacitors on the board.

More info needed, model of vehicle, display and if it is OEM or aftermarket and what kind of fade, preferably with a picture as it fades.

[saturation]

SeanB is right, but often its just a loose connection.

I find worse is the labor of disassembling the dashboard and then tracing the wires/cables to the connector.  It can be easy or not.  If hardware were starting to fail [ PSU, controllers etc.,], it would eventually stop working after repeated heat exposure or cause errors in the panel readout regardless of temperature.

Note, if the cable assembly has heat damage, you'll need a new one otherwise it will pop loose again.

[hunsra]

Hi,

Thanks SeanB and saturation.  Here's more information:

Model of vehicle: 2004 Toyota Highlander Limited
Display: Not sure model of the display, but it is a back-lit monochrome (passive matrix, I think) LCD that displays the climate control settings as well as the trip computer's output.  The foreground is black, and the background is off-white.  Sort of like a 90s-era calculator display.  See attached image.
OEM: Yes.
Kind of fade: Digits and other visual elements appear less and less dark as the temperature rises.  See attached image.  Notice the inconsistent darkness of the 7-segment number display segments as well as the fan speed gauge bars.  Ultimately, as the outside temperature reaches 90F, the display completely fades out.  The back light works fine no matter what the temperature, as do all other visual elements of the dashboard, etc.  This is the only LCD display on the dashboard.  The radio is aftermarket and has an active matrix LCD touchscreen.  All other dashboard displays appear to be LED.

Thanks again for any advise!

-Randy

[saturation]

I think that's a connector failure, its commonly reported for that console.

https://www.youtube.com/watch?v=WUtQ-D2btX4&feature=youtu.be

I think this explains console removal better that look like yours:



Good luck!

[hunsra]

Thanks saturation.

I've had it apart before and remember a flat-flex ribbon cable cable between the power supply board and the climate control board, so maybe that's the culprit.  The connection between the climate control board and the LCD display is not a cable, but rather a set of solid pins soldered to the board.  I've inspected it before and it doesn't seem broken, or replaceable without replacing the LCD as well.  I'll take a look at the flat-flex ribbon cable and see if cleaning and re-seating it in the ZIF sockets helps.

-Randy