When it rained yesterday my car started fine, but was spiking to 18V, so I parked it and drove the truck. After it was done raining, the battery was dead and we jumped it. It was just fine and not spiking voltage, but when I got in 3 hours later it was dead again!

Any ideas?

Bad connection somewhere? Putting 18V out is very dangerous to the electronics of the car (and the battery for that matter), be careful.

 

If it is an SC, the regulator is separate. If it is NA, just replace the alternator. It pays to get a Toyota one.

 

I found it I think... the plug for the alternator was missing the O-ring.

For now I have completely sealed the plug with di-electric grease and my brother is going to try to pickup the correct O-ring tomorrow (he is a tech at the dealer).

I'm just glad it wasn't anything too big.