Prius Gen III AC recharging

Check around, but let a pro do it...someone with a good rep for doing honest quality work.

I doubt your A/C should be bad in 5 years, but a professional can drain the system and leak test. If he finds a leak, it needs to be fixed. If it's solid, it just needs to be recharged to spec.

I'm normally a DIY guy, but most times when you "recharge" it yourself with the stuff you get from the auto parts store, you're just doing a short-term fix, and possibly damaging the system long term. Overcharging because you lacked professional grade equipment (and adequate know how) could ruin your A/C.

More so, if you pay a shop to do the work, and the A/C fails because they did it wrong, it's on their head.

 

See if you can find the sight glass in your A/C piping out under the hood. For my generation (gen 1), the proper behavior in the sight glass is to look almost perfectly clear while the compressor is running, but show a brief burst of bubbles each time the compressor stops.

Don't take my word for that being the correct behavior for your Gen 3, because your generation introduced ejector cycle A/C and that could change the criteria for what "correct" is. Where you should really look for the correct criteria will be in your service manual on techinfo.toyota.com.

That's important too because the "correct" sight glass behavior depends on a bunch of variables you need to control: the A/C settings, engine RPM, ambient temperature, even whether the doors are open. Get the conditions wrong, and you can misinterpret what you see.

But anyway, this quick test (and several others you can find in the manual) would be your first order of business, before you even start to wonder if refrigerant charge is your problem.

How do the fins on the condenser look? When's the last time the cabin air filter was changed?

-Chap

 

... ok, it's likely engine RPM isn't on the list any more, as your compressor's electric ... another reason you should definitely be checking the manual yourself and not relying too much on us.

-Chap

 

Chapman's description of sight glass bubbles sounds spot-on, at least that's how it was in the past. I tried looking through the repair manual, for the sort of test where you hold a thermometer at the vent, quantify performance. Without success. But, what I did find: there's REAMS of instruction, assessing and dealing with AC is not trivial, not shade-tree stuff anymore. I would not just get a can and jump in. Talk to your dealership?

My hunch is your AC is fine, you're just expecting too much of it, say with a car parked in hot sun, expecting quick cool-down. I'd suggest:

1. Leave AC off for the first few blocks, drive with the windows down.
2. Then roll up windows, start AC, on Auto, and set temperature high enough that fan doesn't race more than half-speed. This may necessitate a high temperature, 75~80F. Even at this setting you will feel it cooling.
3. As the cabin starts to cool, drop temperature setting gradually, never so much that the fan races. Aim for a final temp around 75F, which should be cool/comfortable.

 

Mmm, since it hasn't been mentioned:

1. Check condition of the cabin air filter.
2. Check cabin air intake (around wiper blades) is clear of leaves and junk.
3. Check front of radiator is clear, undamaged.

If you have ANY grill blocking, get it out.

 

I'm going to second the recommendation to leave Prius A/C service and repair to Toyota Dealerships...but qualify a shop that has a person who is fully experienced specifically on Prius. To add, Texas summers get HOT and on the worst days my 2010 is adequate, but I wish it put out more.

 

It really wasn't trivial ever, there were reams of AC diagnosis instructions for my friend's 1965, and there have always been plenty of people driving around with overcharged AC, contaminated AC, you-name-how-they-fubared-it-up AC, but maybe what was different then was everybody had the excuse that the service manuals and proper tools were expensive/hard-to-get, etc.

These days, with the manuals right there on techinfo, manifold gauge sets fairly easy to buy, and the diagnostic info you can read from the car, there's probably less excuse for just jumping into it like a bull in a china shop. Somebody who wanted to learn a bit and do it right would not find it impossible to do. But knowing a good shop would save that trouble.

In looking through the manual, did you happen to notice whether Gen 3 even still has a sight glass on the liquid line? If so, were the diagnostic guidelines for viewing it simple enough to give a quick summary here? (If the answer is "hard to summarize, better to read the original" I understand - I'm mostly just curious whether there is a sight glass on Gen 3.)

-Chap

 

Pretty sure that's her, in between grey cap with "H" and the black connector. Engine coolant reservoir is on the left, for orientation.

I've never checked it, think you'd have to put the car in mtenance mode, to keep it running when warmed up.

 

Yup, that's it. About maintenance mode, I would expect more of that kind of thing for my Gen 1 (where the engine drives the compressor - though Gen 1 also has a MAX button that does everything needed for that). The Gen 2 and Gen 3 electric compressor being independent of the engine, I'd think the procedure might be simpler ... though it's also a variable speed compressor so maybe there's some control panel setting you need to make sure it's running at a particular speed for the test. Or even a command from Techstream. Does the manual give a test procedure?

-Chap

 

You got me in gear.

 

Thanks! What's on those first few pages is most useful, because that's the stuff anybody, who doesn't even have a manifold gauge set, can easily check before going all my-AC-doesn't-work-so-it-must-need-refrigerant.

It's good to know that the basics (no bubbles in normal operation below 95°F in cabin, brief bubble burst right when compressor stops) are still the same in Gen 3 as Gen 1. I even see later on that the Gen 3 charging routine (charge to 100 grams more ±50 after the bubbles disappear) is still just the same as for Gen 1, even with all the newfangled ejector cycle technology and whatnot.

I wonder if it's the same for the plug-in too. I got lost in the parts drawings for the A/C in the plug-in and it seems to be a lot more complex than the regular Prius....

-Chap

 

Thank you very much!
That info is very helpful if I ever have to diagnose the AC system.
FWIW, recently read typical automobile AC systems leak 10% of refrigerant per year (CU article?). If correct, those of us keeping our Prii over 5 years will quite likely run into this situation.
Cheers!

 

??!!

Ok, that just made me go outside and check my own sight glass under the specified test conditions. My Prius is a 2001, fourteen years old with 225,000 miles on the clock. This is the first time I've bothered to watch the sight glass, because I've never noticed any problem with A/C capacity. I did have to re-shim the compressor clutch a couple years ago, which cost about a buck.

I did see some continuing bubbles in the glass with the compressor running, and it was less than 95°F in the cabin, so it is probably true that here in year 14 my refrigerant charge is borderline low. For my Gen 1, the specified charge is 500 g, and the charging method is to add 100 g more past the point where the bubbles stop. So, as I'm seeing bubbles, I might have lost at least 100 g leaving it at 80% or slightly below. (I don't really know how much lower than that it could still go with me having no complaints about the cooling.)

I've had the car 8 years and know none was added in that time ... assuming in the worst case the prior owner topped it off just before selling (you'd think they'd have mentioned), then at a 10% per year leak rate I'd be down by 285 g by now, more than half.

If nobody ever topped off in these 14 years, I should need 390 g by now.

I guess I should top it off, find out how much it actually takes, and come up with a leakage rate from that.

It also would not hurt me to spend an hour or two straightening fins on my condenser. The Gen 1 design with the HV radiator in front kind of protects the bottom half, and my grille block protects the whole thing in the winter. But the top half is looking pretty restricted by now....

-Chap

 

In various vehicles we've had over the years, I'd always see a FEW bubbles whisking by, while the compressor was running. FWIW