Optiplex 745 problem - diagnostic lights 1, 3 & 4


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Optiplex 745 problem - diagnostic lights 1, 3 & 4

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Hi, My son's 2nd hand Optiplex 745 has suddenly stopped working, it wont boot, there is nothing going to the screen but the fan etc all seems to be working.

I checked the diagnostic lights and have 1, 3 & 4 lit.

That specific combination doesn't seem to be detailed anywhere.

From looking about, I think it is a problem with the memory thingys.  I have tried removing them one at a time (I have two) and putting them back in but no change.

I am not very techie, so please be gentle, but I would really appreciate any help you can give.  :o)  


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  • Hi Anne,

    As you have guessed, 1, 3 and 4 most likely indicate a problem with the RAM modules. One suggestion would be to remove both modules (or thingys), then replace one of them in the slot marked DIMM1. If you get the same error, try the other one in the same slot. If one of these enables the computer to start without error, then replace the bad one. However, diagnosing the specific problem can be tricky. Should this not work, I might recommend you bring your son's computer to a local computer shop for diagnosis and repair.

  • Thanks for your help Osprey - I just tried that and no joy - as soon as I press the start button, lights 1,3, & 4 are lit but no light 2.  Is it possible that both modules would go at the same time?  Is it worth buying some new ones and trying that?