Pi Zero W, won’t boot on new card or existing. (Both cards OK in a different Pi Zero)
The Pi, I think, suffered water ingress along the area of the GPIO pins.
Now it just does three short green flashes and one long(er) green flash.
Is there any hope of a fix for a freshly bathed Pi, or is it knackered?
Three short green flashes is the generic boot error, four short flashes is a failure to find or load the start.elf file. There isn’t a set code for three short and one long. (The full list is at Raspberry Pi Documentation - Configuration )
Did the water get in at the sd card end? If so its probably a short/fault caused by water under the sd card connector.
There are a fair few components near the sd card connector and any one could have failed or shorted out.
I’d start with a good visual inspection to see if there is any obvious damage.
Next dry out the Zero, a hairdryer should do.
Then flash fresh image and try to reboot. (Cards that work on one Pi dont always work on another)
If this doesn’t work then without some serious testing equipment, it probably time to join the queue to buy a new one.
One of ours did get wet. We used a microscope to find out that water had got into the layers. A couple of months later it just sprang back into life.
Good luck.
Four months later, tried it again out of curiosity.
Nah, it’s still dead!