LCD screen contrast - slowly fading

The lcd module in the pictures is from pool heater. I have couple related questions:

The text started getting deemer over 2 months until it’s just lit lcd with no visible lettering. What could be a cause?

The brand name version is expensive but cannot find a generic equivalent that has 8 pins. Any suggestions? I have used lcds for Arduino and this doesn’t look like any of them.

The environmental conditions of pool heater room ?

Is the display backlight working correctly or is it just the contrast of the display characters to the background ? This can be voltage dependent. The “hobby” type 1602 and similar displays require a potentiometer to optimise the contrast for the precise supply voltage level.
Does the display have special characters/icons etc. or just a standard character set again like the 1602 and similar devices ?

The manufacturer of the pool heater uses this name: Raypak 013640F
You could buy a new one, but be careful, try not to spent more than 20 dollars.
I can not find details for that display, so I don’t know how the contrast or something else can be adjusted.

It’s like 1602, no special characters. The background lighting is working, only letters faded and eventually disappeared. Not it’s just evenly lit screen.

Cannot find anything for $20. There is one for $35 on Amazon but not prime. Ordered one with prime for $65 (because of return policy and speed of delivery) but this is likely to fail again and wanted to find another source for replacement/repair/workaround.

This is probably correct assumption but still got to figure out and fix it.

You can harden the front of the display with clear plastic spray.

I’d guess that the 8 pins are:
Vcc, Gnd, Backlight, chip select and 4 data lines.

I did once write a bus sniffer for the 1602 and similar displays. If you are attempting to use a standard hobby type LCD 1602, or what ever best matches your existing display, it may help. It’s at: LCD 1602 (and similar) databus sniffer . Post#11 has the latest code.

Check voltage on pin #2 , should be 5 or 3.3V. 3,4,5,6, are D4, D5, D6, D7, or in reverse, on scope there should be pulses with amplitude of voltage on pin#2.
What you have on 7 and 8 ?

LCD has always deteriorated when exposed to UV from sun or UV lamps. Is that the case here?
Heat will also destroy the liquid crystals.


Is there a question? The plastic covering likely stops UV.

Producers knowing that sometime are using protecting plastic sometime not ? I think the problem is with voltage on pin #2

Agree with 79galinakorczak
Before spending $20 on an LCD, check what 79galinakorczak says.
I have seen a similar issue on another "outside" device.
The could be a little (pot) potentiometer on the PCB that controls contrast. Is the pool environment the pot could possible be degrading/failing. Mechanical pots are not a great choice for high humidity situations.
And a pot is significantly cheaper than a display. Maybe just change the pot - if there is one - would be my first step.

= slow oxidation on main PCB

= the same is happen with wrist watch when battery is dying

not necessary, I used pot one time and replace it by 1 resistor, and I am using it on all LCD, so probably there is no potentiometer, in mass production adjusting each LCD manually is a headache

This sort of LCD display with the side "glued" conductor strip is notorious for this sort of failure.
The strip becomes slowly "unglued" from the glass substrate.

Eventually the "strip" peels off and is not re "glue-able".

Use in a lot of agricultural electronic displays, or was used, 10 years ago, not used these days due to this problem and better displays.

As @mvoltin has pointed out, there is a replacement, but it will be expensive because it is probably unique to this product.

Tom... :grinning: :+1: :coffee: :australia:

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Other words , bad design, they do that for purpose to sale replacement.

I think it is lack of quality. They made it and it works and the boss said it was okay.
A manufacturer of a washing machines that makes devices to last 20 years would not use it. A manufacturer of aviation, medical or military devices would also not use it.