How do I fix BL-Touch blinking red during print?

To ease up the process of bed leveling, BL-touch is one of the handiest upgrades you can get for a 3D printer. While it’s great in performance and provides a tremendous advantage, there is one issue that you may face. You may sometimes see the Bltouch blinking red during print. Why does that happen, and what can you do about it?

When the Bltouch starts blinking red, it usually means that it has gone into alarm mode. This problem happens when the probe fails the self-test. A lot of things can cause this failure. Another reason for the probe to blink red very slowly is damage to the wiring. Fixing the problem requires you to figure out the reason first.

I am pretty sure; you are still confused about why this happens and how to fix this. I recommend sticking to the end of this article to find all the answers you are looking to get.

Reasons for the BLtouch to blink red during print

Now, Bltouch usually blinks red in two different ways. It can either be a slow blinking red light or a faster blinking red light. The two distinct patterns indicate two other things. I will go through both of them and show you why each scenario occurs. So, let’s get going.

When the lights are blinking quickly

First, let’s get through what happens when the Bltouch red lights blink rapidly. This problem indicates that Bltouch is in alarm mode. It occurs whenever the machine fails to pass the self-test process. It’s a process where the probe will check up on the whole thing and see whether it’s prepped up for use.

Here are the reasons for this to happen –

  • Most of the time, this issue happens solely because of the pin obstruction. With this problem, the pin can’t mode with true freedom, which can occur for various reasons. For example, it can damage the probe that’s causing this. Or the obstruction can come from dust or dirt.
  • Sometimes, the probe will fail the self-test when the pin keeps hitting the probe build plate.
  • It can also fail the test when the probe’s speed is too slow. Any problem with the Z-axis homing can result in this problem.
  • Any physical damage to Bl-touch can also be a major cause because physical impairments can cause the pin to function improperly.

Other than these, sometimes firmware issues and defective probes can also be the reason for a fast-blinking red light on BLtouch.

Related: Ender 3 Pro BLTouch Installing

When the lights are blinking slowly

What does it mean when the lights blink slowly? The lights flashing slowly is a bit more serious than the other problem. This slow flash of lights usually means that the probe faces wiring issues. Damaged wires or problems in the wire can cause the lights to blink slowly.

Here are the reasons that can cause the lights to blink slowly in your Bltouch –

  • The most common reason for a slowly red blinking light on your Bltouch can be +5v reverse wire. When the +5V wire on the Bltouch is somehow reversed, it can cause the probe to blink red slowly.
  • Another reason for this problem can be the faulty wiring. If the wiring with the board is somehow messed up or done wrong, it can cause the lights to blink red slowly.
  • Aside from that, actual damage to the wires can easily result in this issue. External damages can come from various things, such as cuts or pressure from any external source.
  • Lastly, there is the issue of a damaged pin. It’s pretty similar to any external damage to the wires but just on the pin.

One thing you should be aware of is that the BLtouch still works with this issue persisting. But it would be best if you didn’t keep using it while it has this problem. So, make sure to solve this problem as soon as you can.

Solutions to the BLTouch blinking red during print

Once you figure out the reason for the problems occurring, you can easily get them fixed with a little bit of attention. Here’s what you do –

Fixing the lights blinking quickly

To fix the issue of the lights blinking quickly, you have to do the following things –

  1. First, you have to clear any obstruction of the pin. Make sure that the pin is moving up and down properly and freely. Without this, the BL-touch will certainly malfunction, resulting in the quick blinking light.
  2. Try lifting the pin a bit higher so it doesn’t keep hitting the build plate of the probe.
  3. Next, you have to ensure that the Z-axis homing is working properly. You can speed it up to solve the problem for the most part.
  4. Lastly, you can try to solve the firmware issues with an update or re-installation.

However, if you have anything damaged, you will need to replace the part as you can’t repair them.

Related: Install BL-Touch on SKR Mini E3 V2

Fixing the lights blinking slowly

I will be very honest, fixing the lights blinking slowly is very easy, and it’s mostly about rechecking the probe. Let’s check out how you can fix it –

  1. The first thing here is to check on the connection on the wires. Whether they are aligned properly or they are reversed is very important. Make sure the alignment is perfect.
  2. Next, you have to make sure all the pins on the wiring board are clean. Also, the wires are correctly connected to the board.
  3. Make sure the headers on the wires sit properly on the board pins. Any wobbling has to be removed.

If the wires or pins are damaged, you need to replace them with new ones. So, try doing that as a solution if you are dealing with damages.


In summary, touch red light blinking is a very common issue that you can easily solve. All you have to do is learn why it’s happening and then work on fixing it. The solutions don’t require too much work either. And at the end of the day, the auto bed leveling features are still worth getting in your 3D printer.


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