Improve A/C cooling in 04 Prius.

if the air doesn't come out as hard, you should check the fan and filter.

 

Dude... it's been >110°F EVERY DAY! You can't expect it to blow frost at you.

Replace your cabin filter just because it probably needs it.

ALWAYS run A/C in recirculate mode to allow it to cool optimally.

To check your A/C system w/o tools:

Turn car on. Set A/C to full blast, windows open, fresh air intake.

Open hood. Find sight glass at high pressure connection on left (circled in red). Wipe it off. If you see bubbles, you need to add R-134a obtained from wal-mart or a parts store. I recommend wal-mart... about $4.88/can last time I bought it a couple weeks ago. MAKE SURE IT IS STRAIGHT 134a. NO OIL. NO O-RING SEAL. NO DYE. JUST PLAIN R-134a. PERIOD. UNDER NO CIRCUMSTANCES ARE YOU TO USE SOME KIT OR OTHER SUCH ITEM THAT CLAIMS TO IMPROVE YOUR A/C. Those kids contain PAG oil that will potentially damage your expensive compressor.

The low side is indicated by the blue arrow. You have to look down in there. You'll either see a gray cap that says "L" or what looks like an oversized tire valve. That's the low side. You only put it in there.

You'll need a hose and can tap. Again, readily available from Walmart or an auto parts store.

All three of my Prius' needed about half a can this summer... 03, 07 and 08 models.

If that doesn't get you where you want to go, the only thing you can do without replacing parts is to get a full system evacuation and recharge. Either go to a Toyota Dealer, or go to a shop that knows Prius systems inside and out. The equipment shouldn't even be used on non-hybrd cars to prevent contamination of the system with non-hybrid oil.

 

1. Check the cabin air filter and replace if necessary.
2. The refrigerant level may be slightly low due to a minor leak, which results in less efficient AC operation.
3. Do not add refrigerant oil since the special ND-11 oil is required. There is no need to add oil unless you have a major leak or are replacing the air conditioner compressor.
4. If it is necessary to add R-134a refrigerant, make sure that the can only contains refrigerant (and not oil or leak sealant). Use a low pressure gauge and observe the spec which is 29 psi. Do not overfill as generic instructions would have you do.

 

Patrick, I have immense respect for you and your Prius knowledge; however, this is not sound advice. It contradicts the repair manual procedure, which is as I describe above (in part). R-134a high/low side pressures are completely dependent on ambient air. 29psi low side would only be appropriate if ambient air temperatures were 65°F.

The sight glass method ensures proper refrigerant phase regardless of ambient conditions.

Under no circumstances should you use this on your Prius.

Steve

 

The spec assumes the following conditions:

Temperature at air inlet 86 to 95 degrees F, recirculation on.
Blower speed high.
Temperature MAX COLD.
AC switch on.
Fully open doors.

The last four conditions are normal procedure when recharging refrigerant in a typical vehicle.

 

I agree completely; however, the 29psi low side pressure for R-134a is completely off the mark. Low and high side pressures for R-134a CHANGE with ambient temperature.

The first thing they say to check is the site glass. If bubbles, "add refrigerant until bubbles disappear".

The range Toyota gives is not accurate according to their own sight-glass criteria and way off the mark per most other. While 29 psi is the average of the listed 22-36psi, it is misleading to establish this as a limit. It also doesn't account for a compressor that may not be operating at max efficiency due to age or other wear factors.

I can tell you from experience that in almost every case, you will be at or a little above the upper limits for the low side pressure at the prescribed ambient temperature when you add sufficient R-134a to get rid of the bubbles.

Are you basing this on data or "feel?" You're complaining about your A/C on the hottest weather we've had in the last few years...

You're also aging. You might be putting on weight - all subjective things that could influence it.

Point is that without actual data, you can't really say that it's working any differently than the last two summers, particularly when the last two summers were a little cooler than this one.

Best to "keep 'em separated" to drive it home that they should never be interchanged.

No. Sight glass per the manual. You will probably go over 29 psi.

Or the two together. Site glass first. Confirm with pressure. STOP when the bubbles stop.

Early morning/late evening is what it's going to take to get to the 86-95°F range.

Car parked in the sun makes a huge difference. I personally use sun shades and crack all my windows at least half an inch to try and keep interior temps as low as possible. If they're elevated, I'll drive my first 1/4 mile with the windows down about halfway to flush out the searing hot air in the car with the cooler outside air.

 

When it's 110-118°F (or higher), it's not going to cool off in a 20 minute drive. Yes, it will blow cool, but it's going to be on near full blast the whole time even on recirc. The interior will never get uniformly cool where the A/C will turn itself down unless you have the temp set to > 80°F. I leave mine on 78, and it NEVER catches up to the set point on my 25-30 minutes drive home.

It's effin' hot out there, dude...

 

Hey guys,

I've run out my techinfo days for the time being, so I don't have the Gen 2 manual in front of me. But I remember that the Gen 1 A/C was a subcooling condenser design, which meant the proper charge was not right when the bubbles stopped, but so-many-additional-grams-of-refrigerant (100g if I remember right) after the point where the bubbles stop ... which of course involves having a decent scale to rest the refrigerant can on.

Gen 2 is still a subcooling design, is it not? If you've got the manual handy, does it not still say a certain additional weight of refrigerant after the bubbles stop?

If you just stop when the bubbles do, you'll have put in the proper charge for an oldfangled A/C system without subcooling, but it'll be a bit undercharged for the Prius.

But all of that also depends on the exact ambient temperature range and operating conditions (doors open, etc.) specified in the manual ... if you do it when it's really effin' hot out, you'll probably never see the bubbles totally stop, or you'll overcharge the system trying to make them stop.

-Chap

 

one other thing is to make sure your condenser isn't packed full of dirt and bugs. if it looks dirty, you can blow it from the inside out with compressed air. I have used wheel cleaner on my home condenser when it was clogged, I don't know if that would work on a car though.

 

Maybe check out the dealership's charge for an AC service?

 

Yep. Bubbles stop + 100g (75 - 125g), but it's phrased as "may need to be charged after bubbles disappear"

(Total Qty: 450 +-30 g (15.9 +-1.1 oz.) )

For simplicity's sake, I have found the bubble-stop method to be sufficient on all 3 of my cars in Phoenix weather, but I like your idea of a scale. I have a 0-500g scale that would more than suffice. I'll try that next time.

We've discussed the need to do it at lower ambient temperatures (86-95°F per the manual) above.

 

Many opinions expressed here.

The first question is whether the OP's AC system needs help. If he thinks the cooling quality has diminished, it probably has. However that is up to him to determine.

In an effort to be somewhat scientific, I will provide one data point from my 2004, taken at 5:15 PM Mountain Standard Time this afternoon (AZ does not observe DST). The AC system on that car has remained untouched since the car was built in 2003.

The sight glass shows no bubbles. The ambient air temp is 100 degrees F according to the Prius temperature gauge. The car had been driven slightly more than 15 minutes after being parked outside at a local movie theater, returning home. The car is set to Auto AC with the cabin temp set at 78 degrees F. You can see that the air coming out of the center left vent is below freezing temperature. That is how it should be.

Steve correctly cited the spec for refrigerant amount is 15.9 ounces. Since one can of R-134a contains 12 ounces, it is possible to overcharge the system without trying hard. Hence my suggestion that the OP observe the low side pressure when recharging.

However, even if he overcharges the system, if it works better than before that is goodness, and assuming the system has a small leak then the excess charge will leak out as time passes...

Here is a link to the Walmart product that I have bought recently (for my daughter's 2007):
Speed Steed R-134a Auto Air Conditioning Refrigerant, 12 oz - Walmart.com

That car has a very small leak in the AC system which is not obvious after using a dye, so it probably is in the evaporator area. The leak is tiny so I haven't bothered to take apart the dashboard to get to that area yet.

 

Just wow! 220k miles with AC that still works over 10 years old and gets 48 mpg to boot. Kudos to a well maintained vehicle.