Hayward Aqua Trol LCD Not Showing All Digits

Hi - my Aqua Trol LCD is not showing all of the digits that it is supposed to. I have worked my way through the trouble shooting manual to test voltages and resistivities and everything seems OK. The one part that I am not sure about is the last voltage test - am I testing the DC voltage between pin 2 and 4? If so then that also checks out fine.

Do I need to replace the DSP board? Or does the LCD portion need replacing?


I also followed the steps in this post, with no change.

One more detail - I had to replace the current limiter on the main board. After replacing the current limiter, more cells were being displayed on the LCD than before replacing it.
@JamesW bad display boatd?
This is exactly what I am wondering. Are there any more diagnostics that I can run?

In the diagnostics manual where it says to check the voltages on pin 2 and pin 4, do they mean check the voltages between pin 2 and pin 4, or the voltages from a reference to 2 and from a reference to 4?

When I check from 2 to 4 I get 5 V. From 1 to 2 I get 1.5, and from 1 to 4 I get 3.5.

Is that what I should expect? Or does pin 2 have low voltage?


TFP Expert
Mar 2, 2011
If you know how to replace components on the board, you should be able to fix it.

I don't know about what parts you need, but I would suspect that it's just the LED display.


Well-known member
Dec 10, 2018
Have you seen an ancient calculator or DVM LCD with missing segments? Most likely, the zebra connector between the LCD and PCB is shot. A simple and easy fix but can get worse if you are not technically inclined.
You will have to remove the 3 screws in the back to get access and clean the contacts. Be very careful not to crack the lcd, you are warned! Watch this youtube video to get an idea.
Replace the Display Board if you are not comfortable working on it.