3.5" LCD won't work with Fan Shim

If look at the fan shim circuit board, the round pad on the end opposite the one mounting hole is GPIO 17, physical pin 11.
If you look close you’ll see a circuit track / trace going out the bottom of that pad and then turning towards the switch. If you take an exacto knife and carefully cut that track so there is a thin gap in it. That pad will no longer be connected to the switch.
Like you’d do to change the i2c address on a breakout board.

If that is the only track going to that pad, I would think that “should” do it.
I have a fan shim, I don’t have that display though.

Where I have the white line in this picture. If you carefully scrape the black paint off you should see a cooper track under it going down and then left. Cut that track so there is a gap in it. Do this at your own risk.


I made the whole bigger (Pin 11) , which destroy the copper trace. There is not any difference, beside that push botton is gone, still not able to have the LCD working :-/.

I am lost :-O
These is what I tried:

  1. LCD only (drivers and services) without any changes on SW -> LCD works
  2. Fan (drivers and services) only without any changes on SW -> Fan works
  3. LCD with Fan without any changes on SW -> Board does not boot

I dont have a clue what is going on. Pin 11 is the only pin that is actually use by both devices (LCD and Fan). The connectivity on the fan side is gone since I made the whole bigger and there isnt any contact with the pin.

Is it maybe because the fan or is draining too much current that affect the LCD?

Any ideas what else to try?

To be honest I was doubtful it was the button doing it, but stranger things have happened. If its wired up the way I think it is, it only grounds that pin when and while pressed. If you don’t have you finger on the button that pin should just be floating an open circuit. Anything else that wants to use it should be able to use it.

Are we sure its not booting up? Maybe the display is just garbled? I’m not sure that helps but I’m just cuprous as to whether it actually fails to boot or not. You could try hooking up an HDMI display.

It does fail to boot. I left it go for an hour on mine and could not SSH into it. Something is different between the Pi 3b and Pi 4. My Pi 3b has been running the fan shim and 3.5 display together for about a month now with no issues. The same parts I gave up trying to get to work on my Pi 4.

Ok, it is in fact not booting up. I have no idea why though?

@Silarous I am going to need your help to get the current state of those pins on the PI3

What I am trying to achieve with this is to know the difference between the Pi4 and Pi3 as far as GPIO configuration and current state.

Please install only the Fan Shim on your PI3 and once is fully online open a terminal and run the following commands:

  1. sudo raspi-gpio get 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40" > fan_full_gpio.log

  2. watch -d "sudo raspi-gpio get 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40"

The previous command will highlight if there is any change on any field. for instance if one of the levels change. Most likely you will see changes in some levels. Please let it run for 2-3 min and Please write down the gpios that change.

  1. Please repeat steps 1 and 2 without the fan and Only with the LCD and rename the output file to lcd_full_gpio.log instead of fan_full_gpio.log

  2. Please repeat steps 1 and 2 with the Fan and LCD, and rename the output file to lcdfan_full_gpio.log instead of fan_full_gpio.log

I am doing the same with the PI 4 and I will compare my finding and try to findout if something can be done at the software level.


Not a problem. I will try and get that done later tonight!

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With Fan Shim, no Display - GPIO 34

With Display, no Fan Shim - GPIO 34

Both situations only have pin 34 that highlights.

could you share your fan_full_gpio.log and lcdfan_full_gpio.log

Sure if you tell me how to find and display a log.

  1. fan only
    sudo raspi-gpio get 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40" > fan_full_gpio.log

  2. lcd only
    sudo raspi-gpio get 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40" > lcd_full_gpio.log

  3. fan and lcd
    sudo raspi-gpio get 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40" > lcdfan_full_gpio.log

when you run these commands you will endup with 3 files : fan_full_gpio.log, lcd_full_gpio.log, lcdfan_full_gpio.log.

They will be in whatever directory you run this commamd

How do you display the log? I know nothing when it comes to Linux. I can follow a guide though. Have to be detailed for me unfortunately.

you can just run the following commands:

  1. cat fan_full_gpio.log
  2. cat lcd_full_gpio.log
  3. cat lcdfan_full_gpio.log

cat fan_full_gpio.log comes back “Too many arguments”

I am having the exact same issue currently using a Pi 4. Trying to work it out but not having too much luck. I have reinstalled the fan shim software as per in this post in GitHub https://github.com/rootzoll/raspiblitz/issues/806, but to no avail!

I am just setting up the raspiblitz tonight hopefully as I’ve managed to ssh in with the LCD removed. Let me know if I can be of any help debugging this for future users, I’m not the best technically but willing!

Here’s a great solution.

  1. Drill 2 tiny holes into the fan connector, on its side, at the very bottom on the connector. (The holes are the width of the pins and drill them all the way thru the connector)
  2. Insert the fan connector “sideways” onto pins 2 and 3, it will stick out instead of up, but it will make the electrical connection and it only takes up a few mm of space when mounted sideways.
  3. Add the LCD on top, lots of pin real-estate is left.

Works! :-)

So having the fan always on is hardly a solution as we can get fan only with a 5V connector for 10x cheaper.

wondering if anyone having solved their shim fan issue with sudo apt-get purge plymouth* has had any further problems? Things like the sudo reboot or sudo shutdown now not working or else?
It might just affect or latest build: #885

Also did anyone have luck with changing the shimfan to a never one? I wonder if this is issue is just a manufacturing error or a wrong update to their PCB?

Removing plymouth might have got through the booting problem but unfortunately not catching the problem early can lead to weird issues later on.

I have tested with a GPIO Expansion board. Physically separating the connection of the shim fan from the LCD did not help my faulty one. Also unlikely to be an EM interference as distance form the board did not make a difference either.

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