Nikon N90s won't turn on

SOURCE: what does A ERR mean?

There are several situations when this message happens and the camera locks up, and almost none of them has anything to do with the cause stated in the camera manual: film DX coding error. (If it is truly a DX-coding error, manually setting the ISO speed of the film should solve the problem. This could happen in cold weather.) Scenario One: when using Alkaline batteries and the batteries are almost exhausted, and yet one continues to shoot. The battery may not have enough power to complete the shutter firing operation (which usually includes: mirror up, close down diaphragm, shutter fire, mirror down, open diaphragm, advance film, and charge the shutter for next frame). The camera could be lock up in the middle of the operation, left with a dimmed viewfinder. Usually an indication appears quite early if one pays attention: when the batteries are almost exhausted, the film advance becomes noticeably slow. In normal situation film advance is very fast and one cannot distinguish it from other noise such as mirror flipping. When the batteries almost exhausted, the film-advance could take almost 1 second, and the noise of film advancing has been mistakenly identified by some as "beep". I think those is the result of over-adjustment for the Premature Battery Indication problem. This scenario is particular to using alkaline batteries, due to the peculiar behavior of the alkaline battery: even when its power is almost exhausted, it still has a pretty high voltage. Solution: replace the batteries and fire the shutter once should solve the problem. I am pretty sure this is normal, since it happened to me several times, and I once deliberately repeated this happening. Scenario Two: At the end of a roll, when the remaining film is too short for one more frame but long enough to fool the camera, the camera could end up with "Err" message. Solution: rewind the film and load with the new one, and possibly fire the shutter once could solve the problem. (This has never happened to me, but summarized from other’s reports.) Scenario Three: I've heard of two reports: happened in the middle of a roll, with sufficient battery power. I have no idea what’s going on. (Could be really a DX-coding problem, which does not necessarily occur just at the beginning of a roll.) Solution: probably should send the camera in for a check. (Also, both reports of this problem occurs while using Kodachrome films.)

SOURCE: I have a Nikon N90s /film 35mm slr. I haven't

If the switches and contacts are dirty that would do it. If that happens the cost of service may exced the cost of buying a used one.

SOURCE: Nikon Fe meter - warm batteries

If the batteries discharged sufficiently to become very warm in just a few seconds then there's an internal short circuit and the internal circuitry has almost certainly been fried beyond repair. To get warm so fast, those batteries will have shoved some significant current through circuitry designed to handle mere milliamps.

Your camera will be repairable using donor spares, but the repair will cost more than buying another fully functional FE especially when you add on the costs of the CLA (Clean, Lubricate, Adjust) service that it will almost certainly need and the likely need for foam light seal replacement. If you buy another FE it will also most likely need a CLA and seal replacement unless there's proof of it being recently done, but at least you won't have the additional costs of buying a donor FE, stripping it for parts and then doing a heart transplant on it.

On balance, yours is best used as a spares donor; you'll get some of what you spent back if you sell it as a spares/repairs example.

Sorry there's no fix, but I hope that you have still found my reply to be of some use. If so, please rate my answer.