On mine all connections are watertight and the generator is a sealed unit. Because of that, if all of the connections, etc. are intact and good this should not have happened. You might look for any connections that might not have been tightened securely enough to keep out the water including the cover of the regulator. If you find this to be the case, disconnect it and dry it out.
There is always the chance that good old Murphy is at work here, just a pure coincidence the system quit at the same time you rinsed it down. If you have the point type regulator on the firewall you might try firm but non-destructive taps on it with a hammer to see if you can jar the points in it, getting it working again.
On the elementary but have to ask side, has the anti-freeze and/or water caused your fan belt to slip, does it need tightened or replaced? Antifreeze can be "slippery". The generator pulley is small so the belt has to be right to drive it as it should.
Good luck! Regards Martin
