HI i'm new to this forum so please be gentle with me , i have a 12volt car radio that is 12volt dc input will this run ok on a transformer that has 12volt ac output ?
No, and bad things would happen. The 12 VAC needs to be rectified to DC and also filtered. Therefore, you would need to add full wave rectification to the output of your transformer and then filter it with some capacitors to get what the radio would see from a battery.
Also, the transformer would need to be able to supply the current required by the radio. So there is more to it.
Since you didn't put in a location when you registered for this web site, I don't know how to help you. Around here, I would purchase a ready-made 12Vdc regulated power supply for a surplus electronics store for a few $