I have a 1994 Flareside and when I drive through a large puddle when it rains my alternator will drop as well as my pickup will stall. I have replaced belt, tensioner and idler pulley. In dry conditions no issues at all just when wet. My question is I have the lower trim pieces all installed but is there a piece that perhaps is not around the wheel wells or under the radiator?

 

What exactly do you mean by "alternator will drop"? Does that happen at the same moment that the engine stalls; just before; or just after? How long after hitting the puddle does the engine stall? How long did you own it before this symptom appeared? Was it ever able to go through a puddle? What was wrong with the belt, tensioner, & pulley that made you replace them? What did you replace them with (brand, PN, source)? Did each replacement pass the same test that the previous part failed? What happens if you have the engine idling, and you run water onto the belt?

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Let me qualify this, the voltage will drop and battery light will come on. This will happen before the truck stalls. Now my wife had it stall on her after going through standing water or (puddle on steroids) during a hard rain. It is my everyday driver but I do not drive it everyday and when it did happen to me i was mindful for standing water during a hard rain so feel safe to say it has always done it. What concerned me was it shut off and no steering, now it did start right back up.I replaced the belt and tensioner and idler pulley about a year ago as I was in the driveway and went to leave no power steering, looked at my volt gauge and 8 volts. Opened the hood belt was off which I thought was odd put belt back on started truck, belt came off. So I replaced these components and no issues.

 

There might be a bad place on one or more wires that go to the alternator..or that are part of the charging circuit. There may not be any issues unless water gets to them and either shorts two or more together..or shorts one or more to ground. Most direct shorts should blow a fuse but if there is somethin that may serve as a resistance between the shorted wires or wires and ground..but still allows current to be flowing where it shouldnt be..it may not blow a fuse. My opinion..having a slightly different diameter pulley on a device or the tensioner wont make much difference..or enough of a difference to cause your issue. I also doubt that enough water is gettin on the belt to make it slip longer that a second or two..unless youre crossing a shallow river. Then I would slow down. I would check for damaged wires..wires laying in places that might hold water but doesnt normally. Electrical plugs that might catch and hold water if water gets to it. I would also try to figure out why the water would be getting up so far into engine compartment. Im sure that this truck hasn't " Always" had this problem. Ford does a better job than that. I have 12.5 x 33s on mine. I live in MB and water stands here often..during and after it rains. Puddles might pull the wheel out of my hands where the water hits the inner fenders..very little water gets as high up as the oil filter in engine compartment. Look at the simple things 1st. Some "tests" that others refer to are hard to do unless you have extra parts..or the correct tools. Over time there are some things that bend..lean..open..close..change that can cause other things to work different than it did from the factory. The key word is "work". An example is..I just changed the clutch on mine..two months ago. Over time the bushings on the clutch pivot shaft had worn also. The last clutch change Im sure the bushings were worn then too. This time I could barely make the truck change gears. I never touched the pivot shaft with anything except the clutch master cylinder plunger shaft. Some folks aint rich and cant afford to replace every little part as soon as there's an issue with it. Also..with the bushings..I didnt replace with a whole new assembly..nor did I use the Ford modification deal that is supposed to permanently solve the issue. The shaft holes were worn too far to get by with only using the mod. I used JB weld steel stick to repair old assembly and still usin the same old bushings. Can't see it workin better back in 91. If you dont have one..get a multimeter and learn how to do the basics with it. I try to use Motorcraft and Ford stuff..but a lot of the time it doesn't matter. Many direct fit parts made by established companies with good reputations are just as good or better than even the factory part. Not tryin to act like a know it all..or teach you nothin..just tryin to take up for you. Things aint always black and white. I have a nice pickup with very little rust and factory paint. 300k+ miles. Stands out in MB. I look after it best I can. Dude I got it from did the same. You do things like you do them. Myself..I have better things to do with my $$ than to spend $180 for a new smog pump. Got a new..shorter belt..free from a bud. Its a gates belt..not Motorcraft but does the same job. W/O smog pump..Truck runs slightly slower..weight from $$ in my pocket I saved losing smog pump is the problem. But runs faster from losing the useless smog pump. I dont care what the codes say or what a meter reads. If it uses an ounce more gas a day..I dont notice. I know it dont smoke or skip..has good power. Federal Law? Like Mary Jane..there are some things that are legal that cause more harm to the O-Zone than me not usin a smog pump. I also think theyre like air filters..if tryin to do right..smog pumps s/b replaced b4 the bearings wear out. An old one is as bad as not havin one at all..just harder on the vehicle. Oh..and I thought the alternator pully bearing was bad..changed alternator..which needed it..but it was smog pump makin racket. It didnt hurt a thing changing the alternator. It made juice..how could I test the rest of it to see if it needed changin? Some people also have to drive the same vehicle theyre workin on to go get parts for that vehicle. Remove a hard to get to part..put it back on..possibly bad..drive to parts store..come home and do all that bs again? Not me. Youre not hurting a thing replacing a part with another thats made to fit that vehicle. You dont have to test nothing.