How to remove the 100 amp Alternator relay fuse on 2.4 4cyl 2003 Camry?

That's because this fuse is bolted on inside the fuse box, you'll need to remove the fuse box and turn it upside down to take the lower cover off and the electrical connectors, then you can access the 8mm bolts that connect the fuse to the main wires

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Why was the battery replaced? Theres no reason the the 100 amp fuse to blow unless the alternator is shorted or you hooked up the battery backwards. I think the 100 amp fuse goes to the alternator. If it was hooked up backwards then you may have engine computer damage.

you can check the alternator by using a digital voltage meter (usually can be found for less than $15)-voltage at rest (after sitting overnight) should be about 12.5 volts, running should be around 15 volts at startup, dropping down to around 14 at idle. Measure at the battery terminals and the back of the alternator, readings should be pretty much identical. I suspect your alternator is bad-you have a Nipondenso alternator, I just replaced my neighbor's and got a rebuilt unit for less than $100, they are very easy to replace by the way. You should check a few things first before getting another alternator-there are charging fuses and relays in the power center under the hood and by the driver's left foot-check them, just in case one has blown. Also, there is an 80 amp fuse right off the positive terminal of the battery-it is bolted into place, you have to disconnect the battery and the sides of the housing for this fuse has plastic 'doors' on the side you pop open for access to the bolts that hold the 80 amp fuse-remove the outer fuses, remove the bolts, it then just pulls out. You can find these fuses at most parts stores for less than $4.

To get yourself by if you can't get an alternator or don't want to replace it yourself, you can buy a battery charger (needs to be a 10 amp charger, automatic is better since it will not overcharge your battery, about $30 or less)-hook it up to your battery when you are not going anywhere, and you will be able to take SHORT trips, running strictly off the battery. If you use lights your ability to travel will be shortened considerably-even using the radio is using battery reserve, so limit all accessories (heater fan too) and don't travel too far, you can only do this for a brief time.

When this happens, there is no charging system voltage (from the alternator). Several possible causes

1. Alternator's regulator has stopped working
2. Alternator fuse (100 to 120 amp) is blown (at battery post or inside Fuse/Relay box under the hood)
3. Wiring between alternator & battery &/or fuse/relay box.

did u check the main fuses. these are the 80 & 100 amps fuse found in the hood of your car. if they are blown, it is possible that it was the result of improper battery connection.

not taped in harness it is bolted into fuseblock on outside of fuse block are 4 little locks holding in part of fuse block using small screwdriver release locks by prying outwards while pulling up on 100 amp fuse when it has released enough it will expsoe the bolts holding in the 100 amp fuse one side is an 10mm the other is a 8mm MAKE SURE YOU DISSCONECT THE BATTERY 1ST

you may connecting it wrongly , please check +ve and-ve both pole are to be fix with proper wire, if will do wrong it will blow fuse.

Look in the fusebox under the hood, at all of the larger 30 amp and up fuses. You probably have a blown 100 amp fuse. If it is blown, note that this fuse is BOLTED in; you cannot remove it without removing the bolts.

Try disconnecting your alternator temporarily. It may have a shorted diode but that would also normally drain the battery too unless it charges over a relay.
The starter relay can't cause this alone and the currents through the ignition switch mostly control relays. If removing the alternator cable didn't work, I would remove the starter (only a few bolts) after disconnecting the ground cable from your battery and try turning it by hand. It should be stiff but not impossible and if it refuses to turn, it may have a short from the field to the case.  It isn't really possible to use a multimeter to check the starter's windings because they are very low resistance when normal (the beast draws 120-200 amps to start) and would look like shorts on a standard meter anyhow.