Reading PS1 disks fine but refuses to play PS2 games

Alright I have been working on a PS2 that I managed to rescue from being used for parts on Ebay, it had been stripped down and sold for not working but I found out that the issue was a broken fan connector which took minutes to fix. I have since reassembled it and its been working fine with older titles like PS1 games, I do have to use a AV cable for them to load since using a composite video cable just gives a disk read error, I would test it with a SCART cable but I don't have one around.