Found this forum today and the threads help me with my changing transmission fluid research.

My unusual problem: When I start my car, a high pitch turning squeak comes from under the hood. It only happens after it has rained or very high humility is in the air, not when it has been sunny and dry. The sound seems like it's coming from one of the components turning by the belts. As I drive, I hear it whenever I stop. The sound eventually away after a bit of driving.

It started a while back. Since it only shows up when it's wet, then goes away, I have ignored it.

Any ideas what this may be?

 

It sounds like the belt tensioner pully is causing the noise. Belts require adjustment for tension after a while so one of your belts could be a little loose. If you have a Haynes manual check it for instuction on how to check the belt tension yourself, I have a different model galant to you so I'm afraid my Haynes manual is different.

If the belt has the correct tension then the pully itself could need replacing.

 

Unless the tensioner pully is loose, thats not the issue. Most every Galant has this problem. First scan and ck the altenator voltage out put. It should be 13.5 to 13.8 volts, if thats ok, check the crank pully, they tend to seperate which causes the belts to be miss aligned.Last check the belt tension. on both belt, if there is any slack they will squell. You will find and adjustment on the power steering pump 14 mil bolts, one under the pump the other on the front of the pump, for one belt and on the alternator for the other belt, that one has a bolt on the side between the alt and the frame rail and one on the back.