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I recently posted a topic discussing that my A/C was not working very well as the cold air would only happen for a few minutes then it would shut off and only air would blow (or air would blow for a while then the cold air would blow). I appreciate all the replies and went to my dealer to discuss the problem. Of course everything checked out ok and of course the A/C was working great when I brought the car in.

Over the last few weeks I have noticed a trend. When my car sits in the sun and gets hot (interior), I have noticed that the A/C will not come on immediatley even when set to max (only blowing warm air). It usually takes a few minutes for it to start. If I open my windows to cool the interior, the A/C will respond and turn on, thus blowing cool air. This will only happen on Hot days when I am running errands and my car sits outside in the direct heat.

So I am thining that the A/C is reacting to the heat of the interior and will not fully come on until the interior temp has cooled down a bit, thus having to open the windows to cool down. Does this make any sense, and if this is the function of the car. I have never experienced this issue with any other car that I have owned
 

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I've never noticed that second problem in Dallas. (Yes, it does get warm here in the summer.) Are you sure that the A/C compressor is not running immediately, in contrast to simply taking a few minutes to start blowing noticeably cold air?

The next time you take it to a dealer for diagnosis, convince them to re-create the failure conditions by leaving it out in the Sun for a while, and have the tech try it while it's still out in the Sun. Of course they don't need to fix it outside, but initially testing it outside can make a difference. I'd bet that previously either someone other than the tech drove it into the shop with the A/C running before the tech saw it, or that it sat for some time indoors before the tech saw it.
 

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Well it's the same with heat. It will not blow air and in fact will stay off till sufficient heat is available then blow that warm air to the cabin during winter. Never knew it works for A/C in the summer too.
 

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This car like most of our new environmental enclosures (new bldgs, houses, offices, etc) is really "tight". So it may be as simple as you need to open a window at least couple of inches (whether air or heat) for the air being forced into the cabin by the AC to have somewhere to go.

You may be seeing this effect by opening the windows to cool the car, when if fact you are allowing the compression of air in the cabin to be released and let the fan operate at max efficiency.

I always crack a rear window an inch or two when I put on heat or air.
 

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An04Prius said:
This car like most of our new environmental enclosures (new bldgs, houses, offices, etc) is really "tight". So it may be as simple as you need to open a window at least couple of inches (whether air or heat) for the air being forced into the cabin by the AC to have somewhere to go.

You may be seeing this effect by opening the windows to cool the car, when if fact you are allowing the compression of air in the cabin to be released and let the fan operate at max efficiency.

I always crack a rear window an inch or two when I put on heat or air.
In the 2001-2003 model, there is a direct path for free air flow from the cabin past the HV battery to the outside. So this model was not at all "tight". Was this eliminated for the 2004-2005? I thought there was a vent to the battery compartment near one of the rear passengers. Is there also a vent from the battery compartment to the outside?
 

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RSnyder said:
An04Prius said:
This car like most of our new environmental enclosures (new bldgs, houses, offices, etc) is really "tight". So it may be as simple as you need to open a window at least couple of inches (whether air or heat) for the air being forced into the cabin by the AC to have somewhere to go.

You may be seeing this effect by opening the windows to cool the car, when if fact you are allowing the compression of air in the cabin to be released and let the fan operate at max efficiency.

I always crack a rear window an inch or two when I put on heat or air.
In the 2001-2003 model, there is a direct path for free air flow from the cabin past the HV battery to the outside. So this model was not at all "tight". Was this eliminated for the 2004-2005? I thought there was a vent to the battery compartment near one of the rear passengers. Is there also a vent from the battery compartment to the outside?
Ah yes, good point. Yes on 04 there is vent for the battery, that you are cautioned not to block, on the passenger side rear, about shoulder high. I wonder, since of course battery has to be cooled regardless of whether AC is on, if it has a fan of its own ?? or what it relies on for cooling. ??

But, you are right, a vent path past the battery would nix my "tight" description...unless there is some mechanism at the outlet to prevent suction back into the cabin.
 

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I wonder, since of course battery has to be cooled regardless of whether AC is on, if it has a fan of its own ??
Yes, it does have a fan of its own. Sometimes on the drive to Vegas, after going over the hills at a high speed, where it takes pretty much the whole battery, on the downhill part, I can hear the fan in there blowing pretty hard. Its pretty loud sometimes, but only on those drives, I have never heard it any other times.
 

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Brian said:
I wonder, since of course battery has to be cooled regardless of whether AC is on, if it has a fan of its own ??
Yes, it does have a fan of its own. Sometimes on the drive to Vegas, after going over the hills at a high speed, where it takes pretty much the whole battery, on the downhill part, I can hear the fan in there blowing pretty hard. Its pretty loud sometimes, but only on those drives, I have never heard it any other times.
Aha ! Thanks for the info. I also suspect then, that the battery cooling system has to have some way of preventing "back flow" into the cabin which might draw noxious fumes into the people compartment. Perhaps the battery fan works continuously to insure a positive ariflow to cool the battery & out of the cabin whenever the car is operating.
 

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Yes, it blows the warm air out of the car down in front of the right rear tire somewhere. Evan posted a picture that showed the path of the air through the cooler. I will try to find it.
 

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