OK, so I had day off yesterday. Cleaned up truck and took it to car wash to blow engine off. After I noticed it cranking slower on every start. finally dead. I charged batteries and got it started, put a volmeter on batteries and dam, 12.05 V and no rise. restart it, dropped voltage to 11.97, no rise. Did I ruin alternator washing it?

 

There is some circuitry in the alternator which may have been shorted out. I'd pull the alternator and take it to be tested.

 

You will be lucky if all you wrecked is the alternator , when you wash these engines you can short out coil packs and cause all kinds of problems , dont wash the engine its much happier dirty.

 

You can wash it theres just a couple of things you need to cover, the alternator being one of them. Also the PCM, FICM, and batteries to name a few

 

And all the coil packs.

 

The electronics are not that fragile......unless there are cracked or frayed components under the hood. be careful when washing any modern engine. No longer can you simply stuff a rag in the carb throat and bag the distributor. Leave it dirty, or wash and blow dry.

 

I've been washing my engines with plenty of water for over 30 years and the only problem on older cars was that spark plugs would get wet and for few minutes I had misfire or dead cylinder before the heat dried it out.
On my cars/truck I don' t hesitate to spray alternator directly although I am trying to avoid electric wires. Electronics are well hidden in the boxes, so no worry about them.
If your alternator went bad because of some water - it had to have a problem before. Test the wire connection to it and if it is really bad, just replace it. New alternators run about $200 and they need new brushes every few years anyway.

 

The problem could be the use of high pressure water from the car wash. When I wash an engine, I do it at home with a hose to rinse the dirt off, not to blast it off.

 

You NEVER EVER wash the top of a Ford gas engine with coil over plug ignition unless you want tons of problems. A small amount of wd-40 on a rag will work wonders.

 

Here's your sign...

 

Mine is the diesel. In any case, i pulled the alternator last night and am taking it to NAPA to be tested. Likely getting a new one I assume.

 

No wonder why you were washing it.

 

I found issue. It was the glow plug relay stuck on and pulling voltage down very hard. All fixed.