Can this external monitor be saved?

January 15, 2023 7:08 AM

The external monitor for my MacBook isn't working. Any ideas for stuff I haven't tried?

I've had this external monitor since June 2018, so maybe it's at the end of its life? Here's what's going on.

When I plug it in, the usual messages about not being connected are visible, so the screen isn't completely dead. But it won't show the laptop screen. The main "symptom" I can see is that the on light fades in and out - when this happened before, it had half slipped out of the plug and it was resolved by plugging it in better, but that's not working this time. It is plugged into a power strip, so I tried a different outlet in that strip and then tried a different strip altogether. I have checked and rechecked all the plugs.

Is there anything else I can do? At four and a half years, is it expected to stop working? I have a very hard time seeing the regular laptop screen, so I really need to resolve this.

Thanks.

posted by FencingGal to Computers & Internet (20 answers total)

If the monitor is four-and-half years old, it should still be fine. I would suspect a problem with the cable that connects the monitor to the laptop. Make sure it's seated firmly on both ends. Also, if you have another computer somewhere, try connecting the monitor to the other computer so you can see if the problem lies with your monitor or your MacBook. And if you have another cable somewhere, try swapping-out the cable.

I'm not familiar with MacBooks, but I wonder if there is a software setting somewhere that determines whether the computer should use just the built-in screen or the external monitor.
posted by alex1965 at 7:18 AM on January 15, 2023

Response by poster: FYI, I've tried plugging the monitor into several different outlets without connecting it to a computer, and the on light fading in and out continues to happen. I unplugged and replugged the cord connected to the outlet, but it still happens. That's why I'm thinking the problem is with the monitor rather than how it connects to the computer.
posted by FencingGal at 7:28 AM on January 15, 2023

Is the power cable firmly plugged in to the back of the monitor?
posted by outfielder at 7:41 AM on January 15, 2023

Response by poster: Yes, I've checked it twice. I also followed the directions on this page.
posted by FencingGal at 7:42 AM on January 15, 2023

I've seen the power light slowly cycle between brighter and dimmer when the monitor isn't receiving any video signal. Not sure if it happens on this particular monitor.

Does your MacBook work fine without the monitor plugged into it?
posted by alex1965 at 7:47 AM on January 15, 2023

Can you try a different computer, or a different monitor connected to your laptop? My guess would be that you've got the video out on your laptop disabled somehow.
posted by sagc at 8:12 AM on January 15, 2023 [3 favorites]

I see five possibilities here:

1. The monitor itself is broken.
2. There's a setting on the monitor that was switched from HDMI to DVI or VGA (assuming that you're using an HDMI cable to connect the monitor to the MacBook).
3. The monitor works, but the video cable is defective.
4. The monitor and the cable are both fine, but there's a problem with the connector where the cable plugs into the MacBook (or possibly a problem with the connector on the other end, where the cable plugs into the monitor).
5. A setting on the MacBook was changed, and the MacBook is no longer sending a video signal to the external monitor.

If it were me, I would look for another computer (or a PlayStation or DVD player or some such thing) that you can use to test the monitor and the cable by connecting them to the other device. If the monitor works, then you can rule out a hardware problem with the monitor and the cable.
posted by alex1965 at 8:14 AM on January 15, 2023 [1 favorite]

Response by poster: The Macbook is working fine.

I have another computer that I haven't opened in about five years. I'll see if it's still working.

Thanks for your help.
posted by FencingGal at 8:42 AM on January 15, 2023

Some of my monitors do the pulsing power light when they are in power save mode, and they don't detect a computer connection.

I have this exact problem with Macbooks (and Windows laptops, when I had them) every few years. There was nothing wrong with the monitor.

Unplug the monitor entirely from the laptop, but keep it powered on. Make sure the monitor has the right connection (HDMI / DVI / etc) selected. Log in to the laptop as normal. Make sure the screen is on. Plug the monitor into the laptop. What happens?

Sometimes, this "wakes up" the monitor, after a few seconds. Sometimes, I need to close the laptop lid and this forces the computer to turn off the laptop display - and thus only use the external display.
posted by meowzilla at 10:04 AM on January 15, 2023

Response by poster: My old computer isn't working, but a friend brought over a different monitor. I've hooked it up to my laptop, and it's working fine.
posted by FencingGal at 10:06 AM on January 15, 2023

Which cable did you use to connect your friend's monitor to your MacBook? Was it his/her cable, or your cable? There's a small chance that the problem lies with your cable, though it's unlikely.
posted by alex1965 at 10:16 AM on January 15, 2023

Response by poster: It's his cable.
posted by FencingGal at 10:39 AM on January 15, 2023

Response by poster: So I decided to hook it up to the Macbook one more time in case the pulsing power light was because it wasn't connected to a computer (thanks meowzilla), and it seems to be working now. I am very confused.

Thank you for all of the help and suggestions.
posted by FencingGal at 10:53 AM on January 15, 2023

Response by poster: However, when I put the laptop back in its vertical stand, it stopped working. So it seems like it only works when the laptop is flat on the desk. Does that make sense for some reason? I've been using this stand for at least a year. It's kind of like this one, but it only holds one laptop.
posted by FencingGal at 11:01 AM on January 15, 2023

However, when I put the laptop back in its vertical stand, it stopped working. So it seems like it only works when the laptop is flat on the desk.

Does it work when the laptop is flat on the desk and closed, or only when it is open?

If it works only when the laptop is open, then the problem is that the computer is going to sleep when you close its lid. While the MacBook is running, make sure it is plugged into both its power cord and the external monitor, and is connected to an external keyboard and mouse. That should prevent the computer from sleeping when you close its lid.

If it works when the laptop is flat and closed, but not when it is vertical and closed, then the problem might be a loose connection between the computer and the monitor cable. You could test this by putting pressure on the connector in various directions to see if you can get it to work.

(The pulsing light means the monitor is in its own low-power "sleep" mode. It’s normal for the monitor to go to sleep automatically if it is not connected to a computer, or if the computer is off or asleep or otherwise not sending signals to the monitor.)
posted by mbrubeck at 11:19 AM on January 15, 2023 [1 favorite]

(And if you’re using a wireless keyboard and/or mouse and/or trackpad, make sure to test them while the computer is running. You might need to recharge them or change their batteries.)
posted by mbrubeck at 11:27 AM on January 15, 2023

Response by poster: It works when the laptop is closed, but I've gotten a power strip with a longer cord and moved it closer to the laptop. It now works when the laptop is in the vertical stand, so I think that maybe the plug was slightly pulled out before.
posted by FencingGal at 11:33 AM on January 15, 2023

The term you are looking for is "clamshell mode". There have been lots of issues with macbooks in this mode.


Google "macbook clamshell mode problem"
For better results, add the model of your macbook, and possibly the model of your monitor.
posted by soylent00FF00 at 4:38 PM on January 15, 2023 [1 favorite]

If it works only when the laptop is open, then the problem is that the computer is going to sleep when you close its lid.

Recentish Macbook models do have to be plugged in to external power to support a monitor when closed. You're not alone; it took me a while to figure out that one!
posted by praemunire at 8:56 PM on January 15, 2023 [1 favorite]

CMOS battery.
posted by Oyéah at 4:39 PM on January 18, 2023