How do i setup my iMac to display on TWO monitors?

It should just work but if it doesn’t this might solve the issue:
1. Launch System Preferences
2. Go to Displays
3. Click “Detect Displays” button.

@timtrueman tried that. clicking that button isnt doing anything at all. its just clicking it lol. no window, no difference, no nothing.

Are you sure everything is plugged in properly? Are any lights on the external one working?

@johnpowell the external is my PC monitor. it has TWO vga inputs..one is currently my pc (working fine and displaying my PC desktop at the moment) the second is the imac plugged in and ready to go, but when i autodetect inputs it says “no input” and kicks me back to the PC. my luck.

What make/model is the monitor?

Sounds like it’s your monitor – not the Mac. Can you disconnect your PC and try it with only the Mac plugged into it? The Mac might not be sending a signal if it detects the monitor is already in use.

its an HP monitor, would that make a difference? its VGA input

@simpleD but what would the point of TWO inputs be then? it HAS two VGA inputs

It shouldn’t matter. What is the exact model number of the monitor?

It would depend on how the monitor controls which input is active at any given point. The Mac may not be sending a signal if the monitor doesn’t detect a connected port – it’s a catch 22.

@simpleD its the “HP w2007”

It is a simple way to test if the iMac is sending a signal. Take the 60 seconds to disconnect the PC and plug the iMac into the VGA port we know works.

It only has one VGA port. If there’s another one it’s probably a pass through or something. Try getting a mini-to-DVI adapter or unplugging the PC’s VGA connection to make it work.

@timtrueman sorry, you are correct, the PC is using a DVI port, and the mac is extended over using the VGA..so still same issue though correct?

the monitor has 1 VGA and 1 DVI. so both are being used. but only 1 is working.

Googling reveals notorious problems with “no input signal” for that specific monitor. I’m not sure what to recommend…

could it be the VGA cable is no good? or is it seeming that the problem is the monitor?

i just spend $30 on the stupid adapter for no reason then!

Try a different cable if you can. Or if you can test the iMac with another display. Any test to limit the variables in play will help. My guess is it’s the monitor (see this).

We still don’t know if you tried plugging in the Mac by itself. If it works by itself, then the monitor is not capable of switching between two incoming signals simultaneously.

@simpleD let me try that now. hold on

didnt work. unplugged it and the monitor went black and said “check video cable.” it doesnt show the mac even with the PC unplugged. when the monitor turns on it shows the inputs and the signals and it says “VGA – no signal” “DVI – Active”

so it looks like the cable is no good then?

Did you disconnect the cable from the Mac? If it failed to make a connection with the monitor, it might have shut off the port. Reconnect or restart the Mac.

@simpleD i plugged the PC back in. are you saying to just restart the Mac as is now and see if that helps?

Unplug everything but the Mac, leave the monitor on, and restart the Mac. In fact, shut down the Mac completely, then restart.

And try turning the monitor off and back on when you restart the iMac. Unplug the PC from the monitor and turn everything off for a few seconds and bring them both back on.

ok guys i appreciate the help. the thing is, i only want this to work with both in at the same time….theres no way im going to keep unplugging and screwing these cables everytime i switch back and forth. the entire reason i bought the adapter was because the monitor had TWO inputs and i wanted to be able to SWITCH back and forth between them when i needed to.

ill restart the Mac, and if that doesnt work, i guess ill return the adapter and get my $30 back. thanks!

I think you’d need an external KVM switch to do what you want to do.

got it working guys. shut down the mac with BOTH plugged in and it worked on the reboot. dont kno why it wasnt working before but it is now with MAC and PC BOTH in and switching is working. thanks for the help…ill never understand electronics. lol.

@futurelaker88 Sometimes things get finicky when you try to hot swap them, especially monitors and the like. I have to put my MBP to sleep/reboot it to get it see my other monitor when it is acting up.