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Overheating problem adding more details

I’m resubmitting this problem with more info. Hopefully this will pinpoint the problem more clearly. Thanks for indulging a senior citizen on a fixed income. My 2003 Sienna minivan overheats when the AC is on. After about 10-20 minutes of running the AC, the air starts blowing warm.(then it cools a bit, and gets warm again. There is a humid and musty quality to the air, and then the temperature gage quickly rises. When I turn off the AC the temperature quickly cools and the car runs with the gage positioned right in the middle range. I have recently had fans replaced, which fixed the problem for three weeks. It started again. I was then told it needed a new radiator and thermostat. These were replaced,even though I told the mechanic the car runs fine with the AC off. Again problem was fixed for two weeks. Now it’s starting again. (When running the heater, not the AC, the air gets warm and then it starts blowing out neutral or slightly cool air and then fluctuates for a while, before the car gage rises and shows the car is overheating. Going up a hill seems to speed the process along.) Besides getting to the bottom of what is really wrong and fixing it, one of the things I find strange is that both times the mechanics worked on the car the symptoms temporarily stopped. If they have not addressed the problem, why would this happen, and could it be a clue as to what is wrong?

Your best bet would be to have added the information to the original thread. You loose a lot when you split up threads.

Also I suggest splitting up paragraphs. Paragraphs help make reading a lot easier and you are more likely to read and reply.

Just a guess, (I could not read all through your jumbo paragraph) but I would make sure the radiator fans are working, that you don’t have a clogged drain for the A/C condensation and that the blend doors are functioning properly.

One other thought, make sure the air intake is clear, look for animal nests.

I think you have a coolant leak,when they put in the new fans they probably refilled the radiator, when they replaced the radiator of course they filled it. It is taking 2-3 weeks to lose enough coolant to overheat.
Given the warm musty smell in the car I would suspect a leaking heater core.

 PS, I think you need a new mechanic, a local independent shop with a good reputation. Not a chain, and not someone with pretty ads or coupons.

Thank you for all the logistical and automotive advice. It is greatly appreciated

Thank you for considering what may be causing my car problems. The mechanic I’m using actually does have a good reputation and is a small independent shop. For some reason, I believe they have been looking for the obvious reasons for my car’s overheating and jumping to the wong conclusions. Armed with the info you and others have supplied, I’ll have them do a thorough job in diagnosing the underlying problem.