Coin mechanism keeps spitting out nickels - what's wrong

[Tandemdad]

Recently, my coin machine started spitting out a few extra nickels whenever you'd stick a quarter in the machine. The machine is set to dispense sodas for ten cents. Instead of three nickels, it would toss out five or six. Now, when a quarter is inserted, it empties both sleeves of nickels and keeps running trying to dispense more until I unplug it. When I plug it back in, it seems ok and handles nickels and dimes just fine. But stick another quarter in and it spits nickels until it is unplugged. What's going on and how do I fix this problem? Thanks for your help.

A pic of the coin machine is attached.

Btw: this machine is on an old coke machine, css-8-64.

[johnieG]

looks like an early version of a coinco 75-9800/A model. could be a bad quarter micro-switch. or a defective CPU circuit board and/or power supply regulator, I used to fix these, now I just replace them.

cheaper in the long run.