I agree with Roundabout: your best bet likely is to check the refrigerant level. This is very easy -- and there are two routes you could go, depending on how much you want to spend.
The cheaper route (about $20) is to buy a can of R-134a recharge at Walmart or Advance Auto or wherever (a product such as "EZ-Chill") that has a little pressure gauge on it. There are videos on youtube and on the manufacturer websites regarding how to use these products, but basically you'll just locate the LOW pressure port (gray cap marked "L"), start the engine, turn on the AC, and check the pressure via the low pressure port
when the compressor is running. Since you mentioned that your compressor works but isn't running, then you can just add a little refrigerant; if the compressor is disabled by the low-pressure kill switch, then it will kick on for very short spurts as you add refrigerant (and thus disengage the switch).
At that point, you'll know the compressor is okay, but the refrigerant is low. Add refrigerant, while monitoring the pressure when the compressor is running. The pressure will draw down significantly as the compressor runs, and will kill again around 22 psi: be aware that the Rav4's compressor runs on rather short cycles by design, so don't expect it to run continuously, and don't be fooled by this cycling into adding more R-134a than needed! The low side pressure range is 22.8 - 36.3 psi when the compressor is running.
The more expensive route entails the same process, but just requires more precise equipment (long term, this is probably a better way). This route is to go ahead and buy a AC manifold gauge for $50 or so, which will allow you to check both high and low side pressures (again, there are plenty of videos of this process on youtube), and which will allow you to use pure R-134a cans for refilling. The advantages of the gauge set are that you can add pure R-134a and/or compressor oil in a more controlled fashion. (I'm [pretty sure that anything you buy as a "recharge kit" such as EZ-Chill or AC Pro or whatever will have additives, including compressor oil; this is good or bad, depending). If you are going to try to replace any AC components yourself, you'll need to buy the manifold gauge anyway because you'll have to do a full discharge and re-charge. I agree with Roundabout that such an undertaking isn't exactly a beginners DIY, and there are environmental rules for refrigerant collection.
Regarding the coolant, I recommend to use only the Toyota Long-Life "Factory Red" Coolant, part number 00272-1LLAC-01. I say this because I am, honestly, just a Toyota fluids fanatic. I also think that Toyota seals are ultra-finicky and that Toyota fluids are premium and totally worth the extra money. The Toyota coolant last for years and years, so its worth the extra $5 or $10. Please note that this is
not the Toyota "Super Long Life" Coolant, which is pink, and which is a pre-diluted, and which is not appropriate for 4.1's. You'll need the non-diluted Red "Long Life" Coolant.
I also think that using a non-diluted coolant is actually much easier than using a pre-diluted (or 50/50) because you're not going to get all the coolant out, even if you bother to open the block drain (if you want to open the block drain, its on the left rear side of the block -- but I wouldn't bother messing with it if its not leaking). You can save yourself the trouble and get a full flush by just doing this:
1.) Get 10 gallons of distilled water (as eodgator mentioned, this is very important).
2.) If your coolant level with your old coolant is perfect and you know its bled, skip to #3. If its low or you don't know that its bled, bleed it (Lisle funnel recommended, see the DIY below) and add distilled water till you know it is at the proper level -- "proper level" means the coolant will be right up to the "throat" of the radiator opening, about an inch down from the very top where you fasten the cap
when the coolant is cool.
3.) Open the radiator drain valve and record the volume of what you drain. Don't bother with the block drain. You should get about a gallon (3.8 liters) or so.
4.) Refill with distilled water, run the engine to normal temp to open the thermostat and heater core, shut it down, and drain again. Refill and drain doing this process till the distilled water is coming out clean and doesn't smell sweet.
5.) Calculate how much undiluted coolant you need to add: the system capacity is 8.0 liters for manuals and 7.7 liters for automatics. Subtract the volume you recorded in step #3 from the capacity, and that's how much distilled water will still be in the system. For example, if you have an automatic and you got about a gallon (3.8 liters) from radiator, then you know that 3.9 L of water are in the block (7.7L - 3.8L = 3.9L). That's pretty close to 50% water, so just add 3.8L of pure coolant and you'll be just under 50/50. If you want a higher mix, then run the engine again and drain a little of what's been mixed, and add a little more pure coolant (you can do math to get it right where you want it). Then, add 50/50 mixed coolant to the reservoir so its mid-way between the high and low marks.
Here is a DIY for replacing the thermostat, which is a process that requires a coolant drain, so you can see the radiator drain point and coolant system bleeding process:
http://www.rav4world.com/forums/94-...-y-modifications/172553-diy-replace-your-thermostat-get-your-cab-heat-back.html
Please note that it is very important to bleed the system for 20 to 30 minutes after refilling -- you'll be surprised how many little bubbles can hide around that little block. Also, if you have an original radiator cap, I would recommend you replace it at this time: I just had to replace a failed cap on my '00 (17 years ain't bad!) and replaced the cap on a '99 as a precaution. The part number is 16401-7A470 for the 98+, and a lot of people on this forum who have the '96, '97 have switched to the '98+ part because its a 1.1 bar instead of 0.9 bar cap.
A good place to buy Toyota parts is
Local Parts | Local Parts Shop - Auto Parts online wholesale parts - accessories -- they have really good prices.
Good luck and have fun with your Rav!
