A/C only works when engine is running

The 2004-2009 Prius (generation 2) and the newer 2010 Prius (generation 3) both have electric A/C compressors, run by motors powered by the high voltage system. There is no mechanical connection to the engine. There's no reason it should not run the compressor when the engine is off. I haven't particularly noticed the cooling going off - in fact I'm certain I've heard the compressor running with the engine off.

It's possible that the car might turn the compressor off if the demand for power is particularly high. It's worth checking the car over for any devices that might be presenting a higher electrical load than they should be.

A weak 12V battery is known to present a high electrical load to the system, as it tries (and fails) to force more charge into it, so I'd start there.

 

Absolutely, although it is unclear why the A/C would work only when the engine is running. I think you should visit one of the Toyota dealer service depts in your area.

One check: open the hood, make the Prius READY, leave in P and with the parking brake engaged, and wait for the engine to turn off. See if you can hear the air conditioner compressor turn on and a radiator fan spin up, when the A/C button is turned on and you've set the cabin air temp to the lowest temp.

 

I recently made a recording of the A/C compressor sound here:
http://www.youtube.com/v/dsh3fPJyRo4
Hope it helps.

 

We are having the same problem with our 2009 Prius. It was also in a front end accident. did u ever find a solution?

 

Wild guess: Can you check to see which direction your radiator fans are blowing the air?

Can you determine if the AC is working if your gliding at like 35mph with the engine OFF?

 

Excellent suggestion! There have been several earlier reports of the A/C fan blades being re-installed backwards after repair work, in which case essentially no air would move past the A/C condenser radiator except perhaps when the engine fan is running. Be certain that the dealer checks for that possibility. Or, perhaps there was wiring damage and the repair shop connected the A/C fan in parallel with the engine radiator fan.

 

My 2008 Prius blows very cold above say 60mph. At low speeds it is hot. Occasionally, at initial start, it blows cold but then gets hot. Dealer says they can troubleshoot for $85. Prefer to keep that in my pocket. A/C fan versus engine fan? Where are the fans and the compressor located? I imagine the fans are in front, but it is hard to see with the tight front end. Car was involved in front end collision, but damage was primarily above engine on hood. I was pushed into the trailer hitch of a Ford expedition. Seems like problem has existed since then, Crash was in Dec 08, and AC has not been right since. Also seems to recover sometimes if I turn AC off for about five to ten minutes or open windows some.

 

The two fans are located behind the radiator. Turn on the AC and set the cabin temp low enough so that the compressor is running. Get in front of the car, open the hood, and see if you can hear and see at least one fan running. If not, that is your problem.

If the fan or fans are running, see if you can feel air blowing at you as you stand in front of the car. If so, this means the fans need to be swapped so that they are sucking air from the radiator rather than blowing air at it.

The AC compressor is located in front of the engine, mounted low, and has an orange high voltage cable running to it from the inverter.

 

I have the same problem with my 05 Prius (60K). It was involved in a front end collision two years ago. The condenser was replaced with an after market unit. The A/C worked fine for two summers. Last month we started having problems similar to those above. The dealer diagnosed an expansion valve problem and replaced it for $1K. Problems persisted, so they diagnosed the compressor and condenser at an additional $2.3K. I'm having an interesting talk with my insurance company. Any thoughts on relation to the accident and/or appropriateness of the repairs? Any record of this problem apart from a collision? Thanks!

 

Patrick,
Thanks, the driver's side fan is blowing out through the front of the car. What does it take to get the other fan to run? I don't think it was running, but they are hard to see on the road side. That would explain why the AC seems to only work at high speed? Enough incoming air to overtake the fan? However, I did notice this morning, while it was cooler (80-85, it has been in the 90s during the day here) that the AC was blowing cold air while stopped at a light. I will be adding a post about the relationship of "outside air temp", coolant level and AC that may be related to this issue. Now to get my hands in there and reverse the fan flow. Kinda tight at first glance.

 

Yes, you will need to remove the assembly that the two fans live in. Then reverse the mounting position of the two fans, then reinstall.

Note that the two fans have differing blade count. I understand that the fans spin in opposite directions. If they are installed incorrectly, that they will spin in the reverse direction.

The other fan will probably run when the engine gets sufficiently hot.

 

Ok, my A/C problems were finally fixed when the compressor was replaced. Turns out the failure was a result of the front-end collision repair that occurred two years earlier. The body shop improperly recharged the system, most likely using the wrong oil. The hybrid system needs ND 11, a non-conductive oil. The oil most shops use will poison the hybrid system.