Sigma AF 35-135mm 4.5 for Nikon- Faulty lens or user error?

[g-fi]

Ok, a little background, I purchased a camera bag of mixed lenses at an estate sale for something like $5. It was a strange assortment of old lenses, but for $5 I figured if nothing else at least I got a spare camera bag. One of the lenses it contained is, I believe, a Sigma AF-a 35-135mm 4.5 push/pull zoom for Nikon. The inspection sticker on the lens reads 81, so I assume this lens is at least that old. The rear body cap says "Sigma for Nikon" so I gave it a go and mounted it on my D50. Now, it seems to mount fine (but I can't be trusted since I've got a history of putting lenses I shouldn't on my camera apparently heh.) but when I start taking pictures, my camera starts flashing through different numbers on screen like the meter is going nuts and can't decide what settings to suggest. The lens auto focuses, the glass is clean, and the lens itself doesn't appear to be damaged. The contacts are not corroded, the aperture ring doesn't appear to be damaged and all the research that I have done on this lens says that I SHOULD be able to use this lens with my camera. So, what's the deal? I really don't want to use this lens if it's shorting something out on my camera, and the lens has so little relative value that it seems pointless to sell it, is this a lens malfunction or am I once again trying to put a lens on my camera that I shouldn't? It's a shame because the lens really is in good shape otherwise. I've googled the hell out of this and still can't figure it out.

 

[chaosrealm93]

sounds like faulty contacts to me. it happens from time to time with my old 18-105 and even my 24-70. try cleaning the contacts on your body and the lens and try again

 

[g-fi]

Well, I finally pulled the Sigma out to clean the contacts and try again and it's STILL doing it. Frustrating. I cleaned the contacts with a lint free cloth and rubbing alcohol and it made no difference, still getting these wildly varying readings as the camera meters. It happens at all the apertures as well, so it's not that issue where the lens only works wide open or stopped completely down. I am going to send an e-mail into Sigma and see how much a repair would cost, but I'm almost positive that it's not worth it. I checked the contacts in my body as well and they're clean, this issue only occurs with this lens. I guess I can't cry too much since the lens was practically free!