1993 jaguar shorted its electrical out, alternator belt was loose and wasnt charging at idle.

Not a short.
Either the circuit to the battery light is bad, or the fuseable link on the starter solenoid is toast. There is a 30 amp fuse in addition to the fuseable link, plus a 15 amp fuse on the circuit for the battery light.
All of these circuits need to be tested.

The light means a no-charge malfunction. You need to have the alternator tested. Or, possibly, the belt running the alternator is too loose to allow the alternator to work properly. As long as the light is on and engine is running, you are drawing power to run the car's electricals from the battery (not the alternator, as is normal). It won't be long before the battery is run too low to keep the car running.
Good luck.

Vehicles: any failing to keep its battery charged.

A vehicle unable to charge its own battery has one of 4 problems:
(a) alternator failure
(b) voltage regulator failure
(c) battery failure
(d) wiring problem between battery and alternator/voltage regulator.

One most modern vehicles (including 2002 Lexus RX300 - 2WD and AWD), the voltage regulator is an integral component of the alternator and is not separately serviceable.

In the US, one can get a free "charging system diagnosis" from the popular auto parts chains: AutoZone, Advance Auto Parts & Pep Boys. You needn't remove any parts from the car to get this diagnostic, since they can attach a diagnostic meter to the charging system in the parking lot. This diagnostic aid will tell you exactly which component has failed - battery, alternator or voltage regulator.

In case the vehicle is immobile, one can DIY (do it yourself) the diagnosis.
(a) inspect the wiring for corrosion/loose connections/loose connectors/etc.
(b) check alternator belt/pulley - if drive belt is properly turning the alternator pulley (no slippage/misrouting/etc.), then the mechanical tests are complete, and you'll need to continue testing the electrical performance of the charging system components.
(c) first component to test: battery
DIY test 1: remove battery from car and put battery on a 120VAC automotive battery charger and charge it fully (or just check it in the car with motor off, since the car's charging system is a type of automotive battery charger).
test parameter: a fully charged lead-acid automotive battery should read 12.45 volts on a VOM/DMM
DIY test 2: disassemble battery out of car after driving it to one of the auto parts chain stores (Advance/AutoZone/Pep Boys) for a free battery test. These testers will test the battery under load, which is not possible with just a DMM.
(d) if wiring is good, and battery tests good under load, then
the failed component is the alternator/voltage regulator - by process of elimination.
(e) DIY test 3: direct alternator/voltage regulator test (car must start and idle successfully to perform this test)
Start the car, and put a VOM/DMM across the terminals of the battery. Since the car is running, you'll be reading the output voltage of the alternator and not the output voltage of the battery. The acceptable ranges for alternator/voltage regulator output are:

ALTERNATOR CHARGING VOLTAGE

Most alternators that are charging properly should produce a voltage of about 13.8 to 14.2 volts at idle with the lights and accessories off. Always refer to the vehicle manufacturer's specifications. Many Asian vehicles, for example, have higher charging voltages of around 15 volts.

When the engine is first started, the charging voltage should rise quickly to about two volts above base battery voltage, then taper off, leveling out at the specified voltage.

The exact charging voltage will vary according to the battery's state of charge, the load on the vehicle's electrical system, and temperature. The lower the temperature the higher the charging voltage, and the higher the temperature the lower the charging voltage. The "normal" charging voltage on a typical application might be 13.9 to 15.1 volts at 77 degrees F. But at 20 degrees F. below zero, the charging voltage might be 14.9 to 15.8 volts. On a hot engine on a hot day, the normal charging voltage might drop to 13.5 to 14.3 volts.

Here are the full specs for installation of the 2002 Lexus RX300 alternator - you may be able to check these specs yourself (with a torque wrench), or pass them along to your mechanic.

Note: the VIN 8th digit should be "F" for the 2002 Lexus RX300 (2WD & AWD)

2002 Lexus RX300 (2WD and AWD) - 3.0L Engine, VIN "F" SFI DOHC

Alternator

Drive belt. Tension the belt to 170-180 lbs. for a new belt or 95-135 lbs. for a used belt.
Adjusting alternator lockbolt. Tighten the bolt to 13 ft.-lbs. (18 Nm).
Alternator pivot bolt. Tighten the bolt to 41 ft.-lbs. (56 Nm).

Glossary of acronyms
--------------------------------
DIY = do it yourself
DMM = Digital Multimeter
DOHC = Dual Overhead Cam
SFI = Sequential Fuel Injection
VOM = Volt Ohmmeter

References
----------------
How to test a Car Alternator - todayifoundout.com

Alternator & Charging System Checks - aa1car.com

Hi Closet, I think the problem will be with the voltage regulator or a defective alternator. I believe it will be easier to fit a service exchange unit. That will mean removing the alternator from the vehicle. Remove the keys from the ignition. I believe its a good idea to make sketches all the way through the procedure, that way you'll know what goes where. Disconnect the battery and remove the negative. Loosen the alternator tensioner until the belt can be removed. Disconnect the electrical connections. Remove the through bolt under the alternator and then remove the top bolt. Remove the alternator from the bracket. Fitting is the reverse procedure. Make sure the belt is correctly tightened, and you should be away. Regards Johngee10

SOUND LIKE ALTERNATOR FAULTY, BUT FIRST CHECK FOR LOOSE OR SLIPPING DRIVE BELT. CHECK ALTERNATOR FUSE. CHECK ALTERNATOR BATTERY FEED WIRE AND VOLTAGE REGULATOR WIRES MAKE SURE NONE OF THE WIRES IS LOOSE, DISCONNECTED OR DAMAGED.

It could be a loose negative cable or corrosion INSIDE the cable.
There is a main alt fuse in a black plastic case under the hood marked "FUSES" check that.
I would need to know what the alt is putting out at idle and at driving speed.
I would also need to know the battery state of charge.
Make sure your alt belt is not slipping.
Please let me know what you find.

Ok, i understand that you have replaced the alternator, but there seems to be a non charge state in this case. i recommend checking the charging system. use the procedure below to isolate this issue.

Wear protective eye wear and clothing and remove all jewelry when checking your battery and charging system. Jewelry is a good conductor of electricity and is not recommended. Most batteries wear out every 3 to 5 years and need to be replaced. Always replace your battery with an equal replacement battery to assure proper operation. Automotive batteries have a +positive terminal (red), - negative terminal (black). The battery in this illustration has a protective cover over the positive terminal to prevent short circuit in case of an accident. Electricity is stored in the battery and then supplied to the vehicle when the engine is not running. While the engine is running the vehicles alternator charges the battery for future use. (Note: never disconnect the battery while the engine is running. If the battery cable is disconnected from the battery a spark can be generated which can cause the battery to explode or a major electrical malfunction to occur.)

To check a battery surface voltage, remove the positive terminal protective cover. Connect the +positive side meter lead (red) to the positive side battery terminal. Connect the - negative (black) side meter lead to the negative battery terminal. With the vehicle not running and the car sitting over night the battery voltage should be between 12.5 and 12.8 volts.(You will need to use a voltmeter for this testing procedure)

The alternator is rotated by a drive belt driven by the vehicles engine while it is running. Electrical voltage and amperage are generated to recharge the battery and supply voltage to the electrical system of the car. The alternator is held in place with mounting bolts. There is a main electrical wire on the rear of the alternator that supplies voltage to a main voltage junction box. If your alternator is not charging properly, your battery will slowly drain down from operating all the electrical systems in your car and stop the car from running.(most non charge states will be the cause of a loose belt or a low tension rate, due to a mis-adjusted alternator. make sure you have enough tension in the belt for full rotation of the alt pulley)

Next, you will need to check the alternators output with the Amp meter.

Testing the amperage output of the alternator is good for measuring the amount (not the level) of voltage the alternator can produce. This test can be tricky because if the alternator is weak it can still show it as producing amperage. Which is good, but if the voltage is low, it will still allow the battery to go dead. To check the amperage output of an alternator an amp meter is needed. Once the meter is connected start the engine. Next turn on all electrical accessories and raise the engine idle to about 1200 RPM. The alternator should output the max amperage it was designed to produce. Example: a 90 amp alternator should output about 88 amps. Note: An alternator cannot sustain maximum output for long periods of time. If the alternator is forced to operate at maximum output it will overheat and fail. An alternator is designed to operate at max amperage output only for a reasonable amount of time.

((Connect the voltage meter lead the same way you would in a battery static voltage check, Start engine (do not drive) at engine idle the voltage should be between 13.6 to 14.3 volts. If not the alternator may need replacing.)))

found out that motor mount was missing bolt and other was loose which affected alternaror belt tightness alternator wasnt spinning at high enough rpm onceit goes under 1400 it will triger light to come on

Well, you need to find out what is shorting. You can turn the car off and using a Volt/ohm meter on the amp setting, remove each fuse one at a time. The power across a fuse with the vehicle static should be in the milliamp range. How does he know it is drawing 9 amps? You pull each fuse and check in and reinstall and move on to the next one until you find the short.
Some times the alternator has internal shorts. It's pretty easy to remove it and take it to AutoZone for a free test. Just remember to remove the battery cable when removing it.

Hi first check the alternator belt (is it loose...is it there?) if all is ok there then it could be the alternator, have a multimetre put on it it should read around 13.5 if the alternator is doing its job,
Hope this helps

Regards
Steve