What Does This Error Mean?

An HP calculator with a faded screen almost always needs a battery replacement — the LCD requires sufficient voltage for proper contrast. For HP calculators with adjustable contrast, hold the On key and press + to increase contrast or - to decrease it.

Affected Models

HP 12C
HP 17bII+
HP 35s
HP 50g
HP 48G series
All HP calculator models

Common Causes

Battery weak — LCD contrast depends on supply voltage
Contrast setting at minimum (adjustable on HP 50g, HP 48 series)
Calculator stored in extreme heat or cold — LCD response affected
LCD polariser film degraded from UV or heat exposure
Very old batteries leaking voltage below LCD operating threshold

How to Fix It

Replace the battery.

Install fresh batteries according to the model's specification. The HP 35s and HP 17bII+ use two CR2032 cells. The HP 50g uses four AAA batteries. After replacing, the display should immediately show improved contrast.
Adjust the contrast on models that support it.

On the HP 50g and HP 48 series: hold the On key and press + to increase contrast, or - to decrease it. On the HP Prime: go to Settings (Home > Settings > Display) and adjust the brightness slider. This keyboard shortcut is not available on all HP models.
Warm the calculator.

In cold environments, LCD crystals become sluggish and the display appears dim or slow. Bring the calculator to room temperature (18–25°C) and test the display. A faded display that improves as the calculator warms confirms temperature as the cause.
Perform a soft reset.

On the HP 35s: press On + C simultaneously. On the HP 50g: press and hold On, then tap F6 for a soft reset. A soft reset reinitialises the display driver without clearing memory, and can resolve contrast issues caused by firmware glitches.
Check for heat or UV damage.

HP calculators left on a hot desk or in a car can experience LCD polariser degradation, causing a permanent yellowed or faded tint. This is not recoverable by battery replacement. A replacement LCD polariser film is available for some models from electronics repair suppliers.

When to Call a Professional

If a fresh battery does not restore display contrast and the contrast adjustment does not help, the LCD panel or its driver circuit has degraded and needs hardware repair.