A/C only works one hour

Strange... What kind of car do you have Gen 3 or 4 ? 4 cyl or 6 cyl ? Is it manual or automatic a/c ?
When it is " not working", can you hear the fans running under the hood ? Can you hear them start and stop all the time as they should ?
The only thing I can tell you for sure at this stage is that I don't see why it would be related to a an engine temperature problem ...

looks like he has a 96 avalon, they only came in automatic. With only one engine- 1mz-fe v6.

Check the cabin filter. It sounds like your evaporator coil is freezing up, blocking air flow. VERY common problem in the A/C business.
MCTOY

Do you have a XLS. I know the '99 had some AC problems according to MSN, which I thought didn't know shit till what was wrong with my car showed up in there list. You can check it out:

http://autos.msn.com/research/vip/reliability.aspx?modelid=1563

I'd be willing to belive it's the same system. If you don't have climate control you can rule this out. Did you check your AC system pressure? If they are low (on refrigerant) they will kick the compresssor off (clutch disengages), but it wouldn't take a hour to find this out, it would kick off within 5 minutes. Does your A/C light blink when it kicks off?

By the way it can't be the cabin air filter as your car doesn't have one. 2000 was the first year for cabin filter in Avalon, tried to change mine that didn't exist in my '99. That's ruled out.

Ooops! My bad!
Didnt know if it had one or not (cabin filter). A dirty evaporator coil will cause the same ice-up effect. Really anything that slows the flow of air across the evaporator coil can cause ice-up: Dirty filter, coil, dirty or slow fan, crushed or otherwise blocked ducts.....
MCTOY

Yep that's right it's the evaporator that is freezing : one way to prevent that is to not blow too much air with your fans in it (but you can only do that with manual a/c systems...)

wow.....i ahve a 96 camry 5sfe 5spd...my ac wasnt working either....so i charged it today and well....it doesnt seem to work at all...but the condenser or compressor or whatever is engaging....any ideas on that?

EDIT: Oh ya....not working means no cold air at all

96camry4dr,.....
Is your fan (inside) working? I'm not clear on that part. If the system has enough of a (Correct refrigerant type) charge to keep the low pressure switch engaged (ie: compressor runs) and the site glass (usually found on or near the accumulator; looks like small round glass window) is clear, (No bubbles or streaks) I'd say check to make sure the condenser coil is clean. (Dirt/bugs act as insulation, ie: no way for it to get rid of the heat) If there is no cold air at all with the charge correct and fans running, coils clean etc. then you may have bad valves in the compressor, so it cannot develop pressure....new comp. time
MCTOY

Dodo,...
Only other thing (Other than restricted air flow) that might cause it to work for a short time then quit, is if you were SLIGHTLY low on refrigerant charge. As the cabin cools down, the air across the evap. coil is cooler, therefore creating less pressure: ie, there may not be enough heat to create the needed operating pressure to keep the low pressure switch engaged, which would then disengage the clutch. Try running it with 'outside air' selected rather than recirculate. The outside air of course, will be warmer than your cabin and keep the evaporator pressure up.
MCTOY

Thanks everyone!

My car is XLS. Should I change the evaporator valve? When A/C gone (after it used more than hour), the A/C light still is on. How do I test evaporator value?