i pick up this charger used
is there a self diagnose?
it seems to be working fine what are some problems hat happen to these chargers?
what are they worth?

any info would be great

I don't know of a self diagnosis test, but why would you want to do this if it's working fine?

These chargers are fairly reliable. Sometimes they will blow the soldered in fuses. Other times they will burn out the FET's, but not that often.

What are they worth? I'll give you $40 for it right now!

search results... https://www.rctech.net/forum/search....31154083&pp=25
manual... https://icharger.pl/manuals/4010DUO_en.pdf

When things go wrong with the iCharger duos, you usually know right away: won't power on, one channel doesn't show proper battery voltage when connected, won't properly charge, etc. Check ebay completed items for an idea on current prices.