I wouldn't think so. amps is like water pressure. you must always have enough, but more doesn't hurt.
now, I fried a fan because I hooked a .85 amp (850 MA) fan up to a 450 MA 12vDC adapter. I should of used a 1A (1000MA) 12vDC adapter and I would of been fine.
Sorry to resurrect this thread, but I was having the same problem and came across this... which I'm sorry to say is exactly wrong. Well, you're using the right analogy, but drawing the opposite conclusion.
Consider the water pipe. The pressure of the water is analagous to voltage, not amperage. Amperage (often called current) is the
speed of water that is passing by at any time. The amount of water that comes out of the pipe in a given amount of time is then the speed times the pressure; consequentially, the power of the circuit to do work (i.e. apply power to an inductive load such as a motor) is wattage, volts times amps.
With that, consider we want to turn a water wheel, and to do that we need to put 500 gallons of water per minute on it. We have a pipe capable of delivering enough water to turn the wheel. If we send the water down the line at too high a pressure, say 100psi, the pressure will crack the pipe; in electrical terms, the EM field of the wiring will become unstable and break free, often manifested by sparks, arcs, and the blue smoke of death. But if we send it down the pipe at too low a pressure, the wheel won't turn. So, undervoltage = nothing happens, overvoltage = something happens alright, and it's very bad juju.
With amps, say we have a main water line from the city that is capable of delivering 1000 gallons/min. We're only using 500, so the other 500 stay in reserve. But say it can only deliver 50 gallons/min...again, no workee. So with amps, overamperage is okay, because the component will only draw what it requires. Your house's main line from the grid is capable of delivering tens of thousands of amps, but it only actually draws as much as you do. Underamperage yields the same as undervoltage, namely, nada.
So you are correct that you should've used a higher-amperage transformer of at LEAST 1A, but using an underamped supply wouldn't have killed your fan. Maybe it's not a 12V fan? 12V is pretty beefy for a case fan, you may have killed it there by overvolting it. Or it was dead to begin with. But underamping it was not the COD.
i have a 13.5v ac/dc adapter and a 12v fan is it ok to wire it to that?
No! This is a recipe for a dead fan. See above.
This is why you shouldn't post advice that you know little to nothing about, especially when it comes to electricity which, need I remind you, is very freakin' dangerous when you don't know what you're doing. Stay smart, stay safe, and never cross the streams.

As for my problem, I'm sure it's just a bum fan. Aw, darn, I have to go peruse computer parts. Tragedy.