Hi Kukana73, welcome to the forum. I can see you posted about your trailer in the truck campers forum. No worries though the mod will probably move it to a more appropriate forum like tech issues.
Until then though we can most likely answer your question on the blinking light but might need more information from you.
What year is the trailer, does the AC look like it's probably the original or possibly replaced?
Where is the blinking light? Is it up on the ceiling, or inside the filter housing or up on the roof?
Does the AC work when the light is blinking? or if not working or not cooling does it make any noises?
Does the AC blow air but just not cold air?
Any additional information you can give us will help us figure out what's going on.