I put a new alternater in and as soon as I start it up the alternater fails. Alternater is installed properly and belt is installed properly but still fails. 84 toyota pickup 22r engine

If the alternator is on the top in the open, just loosen the alternator bolts a little bit. Then push the alternator to loosen the belt to remove it. Do the opposite to put the new belt on.

If the alternator is buried under a lot of other things, it's a lot tougher job.
Hope this helps.

check the tension on the drive belt can be adjusted to be slack a good indication is when you start up you get a squealing noise from the loose belt, so re adjust, clean the battery terminals

some use just the alternater with a worm screw to put tenso on the belt or the alternater will have a slider where the screwis located that allows you to tilt the alternater up and down to put tenson on the belt

I would have the whole charging system tested with a Volt Meter before you change anything else. You can test the Alternator with a Volt Meter while the engine is running. The Alternator should be putting out between 13-14 volts, anything less and you have a bad Alternator. Check all Battery, Starter, Ground connections for loose or corroded wires and tighten or clean as needed.

Yes, sounds like alternater.Most cars run off battery and the alternater replaces the voltage your using.If alternater is not putting out the car will kill battery very quickly.If you have some basic tools you can change this out yourself.If you have a digital voltmeter to verify the alt is putting out you can charge battery read battery cold,start car and read battery voltage with car running should be between 13.2 to 14.5 volts DC.If battery is reading 12 volts and dropping rapidly,your alt is shot.

Just cause its a new alternator does mean it should work. I would check the charge when running cause it could just be a bad alternator.

There is a spring loaded tensioner on the belt line. You can put a wrrench or socket, usually 15mm, on the bolt and put pressure to turn the tensioner. Then carefully remove the belt from the pulley and gently allow the tensioner to release. When re-installing it. be very careful not to have your fingers under the belt, there is a large amount of pressure on the pulley.

THE ALTERNATER IS DEFECTIVE.
CHANGE THE ALTERNATER.--REMOVE THE SERPENTINE BELT BY PUSHING THE TENSIONER PULLEY WITH A CROW BAR OR BIG SCREWDRIVER. BE CAREFULL TO NOTE THE ROUTING OF THE BELT FIRST, THEN REMOVE THE ALTERNATER BOLTS. INSTALLATION IS THE REVERSE OF THE REMOVAL.

slacken the alternator bolts then slip the belt on the pulleys,using a long screwdiver behind the alternator,lever it out to tighten belt so that the longest part of the belt between pulleys has 1/2 inch movement(too tight and your alternator will need new bearings very soon...)then do up the bolts,check belt tension after all bolts tight to confirm not to tight/loose.

From the top of the car remove the slide and anchor bolt from the alternater bracket. remove your 3 or 4 pin plug and diconnect the pos power line beside the 3 or 4 pin plug ( on the back of the alternater). now raise the car and from below remove the lower bolt that allows the alternater to swing back and forth. the bolt fits through the housing of the alternater. remove the belt. now the alternater is free. this lower bolt that was just removed attaches to a bracket bolted to the block. remove this bracket and the alternater will slide out of the bottom of the car. complete the above steps in reverse to install new part.