05 Ac troubles - Bad compressor?

Hi Folks,

I have a 2005 Prius, purchased 5 months ago with 100k miles, and it currently has 106,000 miles.

The air conditioning blows cool, but not cold. When the A/C is turned on, it makes an unpleasant whining noise. I have a recording of it, but can't upload it or post a URL... if anyone wants to hear it, just message me and I'll send you a link.

It did not make this noise 5 months ago, and the A/C output was colder then. I haven't used the A/C that much over the winter, but it's starting to warm up now and I've noticed it's not doing as well as it used to, and it isn't sounding very good either.

I attached manifold gauges this evening, when the ambient temperature was 80 degrees F (27 degrees C) and noted that with the A/C off, both high and low sides read 7 bar (.7 MPa.) I then turned on the A/C on maximum cooling for a couple of minutes and read the following pressures:

Low side: 4 bar (.4 MPa)
High side: 10 bar (1 MPa)

From the Toyota shop manual I see that the desired pressures (apparently at an assumed ambient temperature of 86-95 degrees F) are:

Low side: 1.5-2.5 bar (.15-.25 MPa)
High side: 13.7-15.7 bar (1.37-1.57 MPa)

Even after adjusting for my slightly low ambient air temperature, it seems to me that these numbers are saying that my A/C compressor is:

1. not lowering the pressure on the low side nearly as much as it should, and
2. not raising the pressure on the high side as much as it should.

Given the noise that it's making and the pressure readings I've found, it seems to me like it's time to start shopping for a new compressor... what do you think?

Thanks,
Silver_05

 

It's at ghostlodgemusic
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Thanks for your responses!
1. I have never seen a mention of vacuuming out the hoses before attaching a manifold gauge in the instructions to this or any other manifold gauge or car. Doing so would cause more refrigerant to be lost each time the gauges are hooked up, and since the pressure of the air in the lines (1 bar) is lower than the pressure in the A/C system (7 bar) it is unlikely that any moisture or air present in the manifold would make it back into the A/C system. If I see manufacturer's instructions indicating that vacuuming out the manifold before pressure testing is a good idea, I'll start doing it. For now I'll follow my manufacturer's instructions.
2. I take cars to a local shop to have the refrigerant removed, then drive home and replace the necessary parts, flush if necessary, vacuum out the system for 45 minutes and recharge it myself.
3. Given the noise it's making and the apparent ineffectiveness of the compressor based on the pressure readings, it seems to me that if I'm going to take the time to evacuate and re-charge the system, I might as well take it apart, install a different compressor ($100 used / $200 rebuilt / $666 new) and dryer element ($20) and maybe more depending on whether I find any shredded compressor guts in the system. I'll also replace the O-rings and keep an eye out for potential leak sites.
As far as I know this car has never been involved in an accident or had the A/C worked on.
Regards,
Silver_05

 

Update: I replaced the compressor, O-rings, and dryer element, and now it sounds like it should and cools like it should.

I found the replacement compressor, ND-11 compatible hybrid compressor oil (which I didn't end up needing because the compressor came with oil) and dryer element for good prices on EBay. Two cans of R134 and O-rings (pack of 24 HNBR green in various metric sizes for $5) were purchased at my local Autozone. Tools required were 10mm, 12mm, and 14mm socket wrenches, 3" socket wrench extension, 14mm hex driver, manifold gauge, refrigerant can tap, vacuum pump, and blacklight to check for leaks.

What I did: take car to local shop to have refrigerant recovered, bring it home, lift the front of the car onto jack stands, remove the left and right black plastic pieces that go from the back of the front bumper to below the front of the engine (extending into the wheel wells,) remove the plastic piece that covers the top of the upper radiator support, unplug orange electrical connector from above, free orange cable from retainers, remove one bolt each from high-side and low side connections to compressor, remove three bolts holding compressor to engine, remove upper radiator support (and a bracket that was attached to it) in order to get access to the plastic dryer housing on the driver's side of the condenser mounted to the front of the radiator, unscrew dryer housing cap from below with a 14mm hex driver (the inverse of a 14mm 6-point socket - a 14mm hex key would also work) to replace the dryer element, then measure 4 oz of oil into new compressor, reassemble, vacuum out, and recharge with 16 oz of R134 with UV dye and no other additives.

 

I was thinking the same thing... why mount the compressor to the engine where it is subject to extra heat, vibration, and movement, when it could be mounted to the frame somewhere out of the way. I'm guessing they just put it on the engine so they could use refrigerant lines similar to those that were used in the previous belt-driven compressor.

I had the refrigerant recovered at JayBee's in Tucson. They didn't charge me for the service, maybe because I've been a long-time customer of the shop. (They did get to keep the $20 worth of R134, but that doesn't really make it worth their time.) JayBees has a top-notch team of professional mechanics who have always done excellent work for me, and they are one of the few shops in town where I can send non-mechanically-inclined female friends to get work done, knowing that they won't be ripped off. The only other place in Tucson I'd take the Prius is Falconworks. They are a shop that specializes in two things: British cars, and the Prius. So if there were ever a serious problem with my inverter or battery pack, the sort of thing you'd want a Prius specialist for, I'd probably take it to Falconworks.