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Discussion Starter #1
Howdy,

AC in my 2007 Sienna isn't working. I don't know if the compressor is bad or if it's just low on freon type stuff. What's the easiest way to figure that out?

If I pop the hood with the A/C off and then turn it on, should I hear an audible difference as the compressor kicks in? Will the compressor kick in if it's low on freon?

I can pick up one of those recharge canister kit things but that obviously won't work if the compressor isn't running... right?

Just want to self diagnose it as far as I can before I end up taking it in somewhere.

Thanks!!
 

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a/c lines are on the passenger side under the hood and run up to the condenser which is behind the front bumper cover. on those lines you'll see a cap labeled H and one labeled L. unscrew the cap and take a little pocket screw driver and press down briefly on the shrader valve. If nothing hisses out you have a major leak and all refrigerant has leaked out.
After that:
-locate the a/c compressor and check to see if the outside of the clutch is always stationary or does it ever spin with the pulley?
-you can check with an auto parts store to see if they'll loan you an a/c manifold gauge set to see what the actual pressures are.
 

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Discussion Starter #3
Do I press the valve on the L or the H or does it not matter?

If nothing hisses out then I assume I can go pick up one of those recharge kit things and see if that will get it going again at least temporarily.

Should the compressor pulley spin even if there's no refrigerant left or is there some sort of safety mechanism that would make that not run? Just wondering if I get no hiss and no movement from the compressor.

I'll check this out after work tonight.

Thanks!
 

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Either the high or low side caps/valves are ok to test. The pulley will always be spinning but the clutch will not spin if there's not enough refrigerant.
 

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First check if the compressor's clutch is engaging. The system is equipped with a high/low pressure switch that will stop the compressor if the system is low on gas. Many times it will start and stop after a few seconds. Turn on the engine with the AC off and ask someone to turn it on while you watch the clutch, if it engages and then stops most likely you are low on gas. Purging the Schrader valves will only tell you if the system is fully empty (massive leak) if no gas comes out and in that case you should take it to a shop. If some gas comes out you could just be low or have an electrical problem.
You could buy a kit and recharge it to the recommended pressure, its quite easy to do (do not overcharge it) but keep in mind that depending on the size of the leak, this repair might not last.


If the clutch doesn't engage at all you could have a massive leak or an electrical problem. I'd start by checking the clutch relay (labelled as MG CLT) located in the engine bay junction box; you can swap it with the horn relay (they are the same) and test the compressor one simply by blowing the horn.


Good luck and let us know what you find.








 

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First thing you need to know is if there is any pressure in the system. Even off, you should have the same static pressure on both the low and high side. The actual pressure is temperature dependent, but I'd say you should see at least 50 psi on an 80'F day or your system might not turn on due to the low pressure safety switch. You'll need a pressure gauge (full manifold set is best....) to test for this.
 

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would think one of the first things to check is the compressor clutch relay...... before messing with the cold stuff. the simplest way to test this is to look up a pic of the relay box on google... simple...search 2007 sienna compressor relay images. several pics will pop up. one should show the A/C Compressor relay location Pull it, its easy. In the same box is a similar relay, the Horn Relay. Search on google for testing Compressor Relay. you should find a couple bits on taking that second relay out and putting it into the A/C Compressor Clutch relay slot. Turn on your van and turn on the AC... you should hear an audible click coming from the motor when you A/C Compressor Clutch engages. The relay is about 15 bucks from Auto Zone etc. If don't hear the click... go the route of the Refrigerant

found this on this web for my 2004. Suspect 2007 is similar.

http://www.siennachat.com/forum/66-problems-maintenance-repair/3370-04-c-problems.html
 

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jman1200 had already mentioned the compressor clutch relay (MG CLT) but it's always good to reinforce this as the first logical step. This is a picture from my old '08 van, and it's the grey relay located above the 10A & 7.5A fuses.
 

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Discussion Starter #9
Sorry for the late response...

I pressed on the valve on the H and L spots and did get a "hiss" when I did that but it didn't sound overly strong.
Last time I bought a recharge for a previous vehicle, it came with a hose and gauge like this one:
http://www.autozone.com/a-c-charging-and-refrigerant-freon/r134a-refrigerant/quest-r-134a-sub-zero-refrigerant-not-for-hybrid-vehicles-with-electrical-driven-compressors/244634/?_requestid=2908757

I kept the hose and gauge and just put it on the L connector and it only shows about 10 pounds of pressure.

Is my best bet to go pick up one of those little cans of stuff and go through the recharge process and see what happens?

Thanks!
 

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With the engine off and thus compressor off, pressures equalize on high and low sides to something like 60-80 psi. So if its 10 psi with the engine off then you're very low. Adding a can or two plus some UV dye might help you find the leak. Ultimately I try use sight, sound, and touch when looking for the leak. After you've filled it up with the engine running, and the air starts blowing cold, shut the engine off and quickly start looking and listening. Follow the lines and look through the grill at the condenser, especially if you see dents from rocks. I actually had the shrader valve itself go bad on mine and thankfully saw it (little bubble's) early on.
Generally speaking, a/c work is pretty advanced so don't beat yourself up if you can't find the leak and take it to a shop.
 

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I think I might have a similar issue. The AC seems to work fine at anything over idle (quite cold actually).
When I drop down to idle...say, coasting up to a corner and applying the breaks. The idle will surge slightly and the AC will no longer be cold. Once I get back on the gas the AC becomes cold again. Every now and then though it will not kick back "on" when I pick up the throttle and I have to turn the system off / on and it'll be cold again. While sitting in the driveway I could hear the compressor clutch going "click...click...click....click" and it seemed to correspond with the surging in the idle. Going down the freeway on a 2 hour drive? Works fantastic, nice and cold.

General consensus that I might need a recharge due to slightly low pressure triggering the high/low switch?

Appreciate the help.
 

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I think I might have a similar issue. The AC seems to work fine at anything over idle (quite cold actually).
When I drop down to idle...say, coasting up to a corner and applying the breaks. The idle will surge slightly and the AC will no longer be cold. Once I get back on the gas the AC becomes cold again. Every now and then though it will not kick back "on" when I pick up the throttle and I have to turn the system off / on and it'll be cold again. While sitting in the driveway I could hear the compressor clutch going "click...click...click....click" and it seemed to correspond with the surging in the idle. Going down the freeway on a 2 hour drive? Works fantastic, nice and cold.

General consensus that I might need a recharge due to slightly low pressure triggering the high/low switch?

Appreciate the help.
 

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I am having the same issue, my ac compressor does not engage. I have a 2008 Toyota Sienna LE with 67K miles. I already replaced the relay for the compressor and it did not help. I am trying to find the low pressure switch so I can jump the compressor to see if it works. I have seen people doing that on youtube but I cannot find the low pressure switch. One more question, when the engine is on and the A/C is on as well, should the cooling fan has to be spinning?

Thanks guys in advance!
 

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Typical modern vehicles have two electric fans. One is thermostatically controlled and runs only when the engine coolant temperature is high enough. The other is connected to the air conditioning system and runs whenever the AC is on. Some vehicles may have additional logic to run the second fan even if the AC is off, if the coolant temperature gets too high (vehicle is overheating or nearly so).
 
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