I bought a used ATL-3 a couple of years ago. It is still working ok and I have quite a few spare parts, but if it died, I don't know how far I would go in trying to get it fixed. I am not particularly handy with stuff like this so I am afraid I would have to junk it for parts and get something newer, like a CPP. The two main reasons I bought it were 1) temperature control and 2) processing 8x10 film. If you are processing 8x10, you will have to use Expert Drums and they don't fit on the smaller machines.
If I were you, I would first talk to someone who has a bit of expertise in electronics etc., and can look at the diagrams in the manual. It might be something very simple. If that doesn't work out, you might talk to Omer at Catlabs. If he can't advise you on what is wrong with it, he will certainly have something to replace it.