Strange Issue With Memory

[PCBudgetSolutions]

So I was working on a customers PC and it would not post video despite the video card turning on.  The motherboard threw an error code: 55 which meant bad memory.  So I swapped memory from my PC, also corsair Vengeance 1600MHz but it's the set I've used for a year.  See the customer sent the PC back to me because it kept freezing.  I redid the OS, changed the memory and it's fine.  So now his memory is in my PC and it seems to be working fine, no beeps or codes during boot, display is fine etc.  I would presume I may have issues down the road when I'll need to RMA this memory, but memory is being weird lol.

[mybeat]

You can run memtest for around 24hrs to check if there's something wrong with mem sticks.

[Leonard]

Have you checked the motherboards memory-QVL for that motherboard?

[mgsstar]

I would run memtest on the ram individually and in a group to see if it creates any errors. I would run each one for at least 12 hours: www.memtest.org