'05 Vibe/Matrix A/C

Take a pocket thermometer and measure the A/C outlet temperature after it has been running for 20 minutes or more. Then drive by your Pontiac dealer and take a test drive in their demo Vibe. If the temperatures vary widely, then I'd say it was time for warranty service.

Back in the late 80's/early 90's, they made the switch from R-12 Freon to R-134a refrigerant. The R-134 was terrible. It took a few years but they found by increasing the size of the compressor they could compensate for the lack of 'cool' from the R-12 used previously. BUT it STILL wasn't as cold as R-12. I have found with my newer cars, the longer the compressor is running (longer trips) the colder the AC gets. A 20 minute ride never reached the cold levels an hour ride would. It seems in both my cars,

You can also increase the effectiveness by using RECIRC (although this can fog the windows up) or by adding tint to the windows. Check local laws; I had a green car with green tint, perfectly see-through, and I had to remove it to pass the state inspection.

Sorry, this doesn't make sense. Running on Recirculate means that you are circulating the same (dehumidified) air through the A/C system instead of bringing higher humidity air in as you would with the system set to 'Outside'. The only reason that windows would fog up in Recirculate mode would be if the drain line for the evaporator was plugged.

Nevertheless, that's what happens. I'd guess recirc mode also prevents the air from leaving the cabin. That plus people exhaling puts more moisture in the cabin than is in the outside air. Also, in defog mode if that's used to keep the windows from fogging up, the windshield gets so cold condensation forms on the outside.

Pat

Bing-go! You have to take into account the Human factor. Just like seeing your breath on a cold day...the moisture has to go somewhere, and is generally condenses on the glass.

Also, if you notice, there is a point to which the AC clears the glass...after that condensation starts on the OUTside of the window.

That is true. However, here in Florida the in car humidity is always lower with the A/C on and in recirculate, even if the car is full of people. Something about the swamp....

"Travis Jordan" wrote: snip

It shouldn't be...what takes the moisture out of the air is when the moist warm air blows over the cold surfaces of the heat exchanger the moisture condenses on the cold fins and runs off overboard. When the air becomes cold (and picks up moisture from the people) then there's not much difference in temperature between it and the cold surfaces of the fins and little moisture will be condensed on them. So you end up with cold moist air.

Don't you?...T'would seem so to me anyway...

Gord,

What you're saying is true unless the outside humidity is really high, like over 80%. Then, the humidity outside the car could be greater than the humidity inside the car. Hot days with 80+% humidity are not uncommon in the southeast and Asia.

The problem with continually running the AC in recirc mode is that the interior air gets stale and the evaporator compartment gets musty so except for the initial cool-down period, it is better to run the car in fresh mode.

You don't know any more about AC then you do about politics, it appears.

It is far more efficient to further dehumidify the dehumidified interior air than to try to dehumidify humid outside air. Do some research before you post on a subject of which you obviously have little of no knowledge, WBMA. LOL

mike hunt

Gourd Seaman wrote:

ALL A/C systems exchange the interior air, even when run on recirc.

Drive any vehicle with automatic climate control, where one sets a desired temperature. Observe how it operates. Once the coil is cooled the blower comes to full on. It starts on outside air to move the hot air from inside the vehicle via the built in rear vents. When the interior reaches a predetermined temperature it switches to inside air. As the temperature you selected is reached the blower speed reduces so that the RATE of cooling is increased as the slower moving air passes over the coil. It will only switch to outside air if the outside air temperature drops below your selected temperature. If the humidastat determines the outside air is too humid it will switch back to inside air as needed to maintain temperature and humidity. Recirc is the most efficient mode of operation albeit it a bit noisier. Automatic system have overrides for those that chose to operate their system differently however. If one read their owners manual it will describe a similar manual selection, for those HVAC systems are manually operated.

mike hunt

Ray O wrote:

I don't think anyone was implying that any A/C system did not exchange interior air

Our 97 Avalon, 00 LS 400, and 03 Sequoia all normally use outside air in auto AC mode unless the inside is really hot after being parked, in which case it runs on high fan speed/recirc for a few minutes and then switches to outside air. The Lexus will also switch to recirc if the system is sucking in fumes, like when you are following a diesel bus or truck.

If the humidastat

I have not read the owner's manual for a Vibe or Matrix, but Toyota usually recommends using recirc for initial cool-down or extreme conditions, otherwise, use outside air to keep the air fresher.

Do you run you home air conditioning system with the windows open to keep the air in you home 'fresh' as well?

I suggest you actually READ the owner manual. Just think you will save some money on fuel once you learn how to operate your HVAC system properly. LOL

mike hunt

Ray O wrote: