Hello everyone,

I am new here, and I have a 1990 F150 with the 4.9 300 I6 5 speed. Everytime I start the truck, my voltage gauge sits on the lower side and my belt squeals. As the voltage climbs back up, the squeal goes away. Any ideas as to what this could be? I have changed the alternator, the belt several times, and the tensioner with no change.

Thank you

 

Is the belt the correct one and is it tight enough? If mine isn't pretty tight it will do that.

 

Are u certain its the belt? If u do think its the belt, try one size smaller. It maybe too large and not enough tension on the pulleys. Also make sure theres no oil in the grooves of the pulley

 

I'll have to check the belt size and tension, I can spin the alternator pulley with the truck off by hand. My belt may be too loose. I'll look into it more tomorrow, all the pulleys were degreased and wire brushed.

 

Ya if you can spin the altenator pulley by hand with the belt attached it is way to loose. The belt should have about a inch of deflection when the belt is tight

 

Have you tried to see if you have play in pulley up down in and out for alternator it may spin free with belt off but be binding bears with belt on plus what name brand belt you running ive had 4 different ones advanced-napa-autozone and motorcraft is on now and doesn't squeal now before it would chirp squeal sound bad ...lol

 

I'm not sure as to the brand of belt that's on there now. And the alternator is perfect along with all other pulleys, power steering chatters a bit, but not a worry. The squeal comes off the alternator. Not sure if the fact that when the alternator is unplugged the squeal goes away is relevant to the bad belt, or if it's the cause of the squeal

 

Never unplug an alt while running.

The squeal is slip. Slip indicates looseness.

The alt works hardest at start. There is an actual increase in resistance to turning when it is working hardest. I bet if you turn on every electrical device, it will squall too.

If you have a parts store that will work with you, you might be able get a fractionally smaller belt. As in a half-inch to inch shorter to start.

Good luck & welcome to FTE