Downtime Eliminator Flexo printing

Welcome to my column where I will share best practices for Flexo Wash technology and common flexo challenges. I want to answer your real world questions, so be sure to send them to me at: and we will feature them in an upcoming column. As your partner, I look forward to handling all your issues as soon as possible and offer lessons learned.

Problem: The Narrow Web Unit Won’t Start.


Have you ever gone out to your Narrow Web Flexo Wash unit, pressed the start button and then the manual rotation popped up on the screen? Have you ever pressed start and nothing happened? We get the call every once in a while where this is the case. Let’s go over what may be the cause of your unit not starting.


First off, on pre-circuit board units (before 2008) there are four inputs that must be present on a narrow web roll/sleeve cleaning unit for the actual wash cycle to start.

The four inputs are:

  • Lid Sensor Input
  • Home Sensor Input
  • Start Button Input
  • Emergency Stop Input

While these inputs are pretty much self-explanatory, let’s look at these in a little more detail.

On pre-circuit board units, if your lid sensor is not sending that 24V DC signal to input #4 on the microcontroller, then nothing will happen on the unit. The lid lock will not engage, the three-way valve will not switch to drain to tank and the diaphragm pump will not come on. You can close the lid and you will see the inputs and outputs on the microcontroller screen. The icon for input #4 must be illuminated. This indicates that you are getting the correct signal from the lid sensor. If all the correct inputs are illuminated (in this case, it would be input #s 1 {wash time 5 minutes}, 3 {start input}, 4 {lid closed}, 5 {emergency stop} and 6 {home sensor}. Please note that depending on what length of wash cycle you have selected (on the switch located on the front of the unit), you may not have an input on #1. If wash time 2 is selected, there will be no input. If wash time 3 is selected, input #2 will be illuminated.

When the wash cycle starts, you will see a timer on the screen start to count down. If all of the inputs are present and you see the counter on the screen but your diaphragm pump doesn’t come on, then we have another issue. The microcontroller may be dropping an output or one of the solenoid valves on the valve block may be bad. Before you call the shop, make sure that all of those inputs are present and we can take it from there. If you are missing an input, then you will need to check the corresponding component for a 24V DC signal (start button, lid sensor, emergency stop and home sensor).

For units made after 2008 that have the circuit board and the LED display, the inputs required are the same. You still need the lid sensor, home sensor, start button and emergency stop inputs but you will also need to make sure that the liquid level sensor has not tripped. This can be seen on the screen as a “low liquid level” alarm. So, if this input is made, the unit won’t start.

On circuit board units, if the lid sensor is not sending a signal with the lid closed, when start is pressed you will see “manual rotation” pop up on the LED screen and manual rotation will start on the unit. This is a very good indication that the lid sensor is not functioning. If you check that lid sensor and you are getting a 24V DC signal to input 18 on the circuit board and manual rotation still comes up, then another one of the inputs may not be present. As with the microcontroller units, if you are dropping any of the inputs, the unit will not start. You can check the wiring diagram for your unit to make sure that the correct inputs are present on the circuit board.

It is important to note, that on circuit board units, if all the inputs are present, start is pressed and the wash time comes up on the LED screen but the diaphragm pump does not come on and the three way valve does not switch from drain to tank, then one of the solenoid valves on the valve block may be bad or the circuit board may be dropping an output.

Give us a call at the shop and we can help you troubleshoot the problem.


As always, if you need immediate assistance, call us at Toll Free: 888-493-5396 | F: 888-543-5396

Flexo Wash US

*Please note new address* 

2010 Plantside Drive
Louisville, KY 40299