Hey guys...Not being very savvy with A/C, can somebody confirm my fear? The air on my 850 has been starting to act up since the end of last summer. It's fairly cold for a while then goes warm for a bit then goes cold again. I charged it last spring and it was fine for a few months. I put a gauge on it today and it is between 25 and 45 psi on the low pressure port but, I noticed that the compressor cycles on and off every 4 seconds or so. Does this mean my compressor is bad?

 

I just recharged my AC system today in my 850 as well cause it was doing the same as your problem, comppressor going off and on quickly and not getting cold in the cabin. Most likely you have low pressure in the system. try not to use it, you can damage the compressor until you put freon on it.

 

1+ with Gaby. Put more freon in it. If it takes longer than 30 days to leak out count your blessings.

 

what they said

 

So, even though I'm at 25-45 psi (which my guage says is in the full range), I'm low? How much more should I add?

 

Has to be low for the compressor to do that. when you add the freon with the car on and AC on, you notice the compressor stabilizing?? also what port are you using to put the freon? is it the one next to the ECU's?

 

Yes, I'm using the port by the ECU. I didn't add any freon yet as my gauge is telling me it's in normal range.

 

You stated you have no cold Air anymore correct?
and the COmpressor keeps shutting off and on really fast right?

thats an indication of low freon on the system. if it isnt low freon which i doubt it you have a short somewhere but thats i dont think possible cause then the compressor wouldnt even activate it. reccomendation take the car to a shop to test for leaks and make sure it does have freon. im at lost here cause i was having the same symptons as you and put freon on mine and problem solved

 

First of all, the pressure should be stable. If it's not solid 45 psi, add some freon. The stuff only cost $8. If you take it to a shop and have them check it out, you'll pay at least $75. Add the freon and if it doesn't fix it, let us know. They system holds what ever the sticker on the strut says it holds and if it's 4 to 8 oz low, it will cause the compressor to cycle.

 

And just to be clear as some people still get this wrong, that's 45 psi with the AC compressor clutch engaged, engine running, AC system on. AC clutch engaged is the main thing as that's the only time the low side pressure you're going to be hooked up to really means anything useable.

 

I've been reading around about this on other websites and reading a lot of conflicting info. One site mentioned that it should be at 60psi and another mentioned that it should be at 45psi and the system won't let you add more once it reaches that.

As I mentioned, it is fairly cold for a bit then goes warm for a bit then fairly cold again (mind you, not freezing cold). That is usually when it is below 80 degrees out. At the end of last summer, when it was over 90, it didn't get very cold at all.

I'll pick up some 134a today and try adding a little bit more and report back on what happens.

 

45 psi is kind of a general pressure. It is not the perfect pressure but it is an accepted general pressure for the DIYer who doesn't have an accurate weight scale or the evacuation equipment.

Depending on the cars type of system (there are variations), the temperature and the humidity the desired pressure on the low side for a properly charged system will vary. There are charts for charging but it's a best guess at an imperfect way of doing an addition. The higher the temperature and humidity the higher the "low" side pressure will be due to more load on the system trying to transfer the heat energy out of the vehicles interior.

If it was really hot, say over a hundred with about the same in humidity it might be correct to go to 60 psi or even a little more but it's unlikely your going to be doing it on a day like that. Some of the cans come with gauges will have a dial that will turn to adjust the sweet spot for the ambient temperature so if you're picking up a can you can check one out. You turn the dial to the days temperature and it has an embossed or raised "V" that gives you an area in psi to aim at. It's still just a guess but it is helpful for the first time DIYer.

It isn't the low side that will cut you off at 60-65 or more psi it's the high side. As you raise the low side by adding freon the high side is the one that is climbing more. What would happen is you would be hitting the high pressure safety switch that would save the compressor from trying to compress an amount of freon it couldn't and either damaging the compressor or blowing a line. The high side safety is somewhere around 550 to 700 psi. I'm not sure the exact pressure but if your pushing 60 low you're likely to be somewhere 450 to 550+ high side depending on temp and humidity.

Trust me, if your charging it on a hot day, 75-90 degrees then 45-50 psi is your best bet unless you break out that chart from the internet and go to a weather channel and get your temp and humidity and plot the pressure for your type of system.

The picture shows a gauge off one of the refill canisters available. It goes red at 55 psi. They don't recommend going above that. The arrow in the center of the two red lines gets placed on the temperature so as the temperature increases so does the recommended pressure for a proper top off of the freon.

 

+1 And the ambient temp will affect the pressure reading also. Should be 45psi at about 75 deg ambient temp. It can be more difficult than you think to get enough freeon in the system if the compressor keeps cycling. I jumped the clutch right to the clutch battery so it would stay on while I filled it. But break the connection every now and then so you don't dmage it. I also put the can of freeon in a pan of warm (almost hot) water which makes the freeon go in very fast. When you have a stable ~45 psi with the compressor running and the air is ice cold your done!

 

Every 850 I have serviced was cycling and took the freon no problem. Just give it a try for the 8th time and see if that helps.

 

If you're in a hurry to get it in, you can just hold on to it with both your hands or put it under your arm and invert the can so the tap is down. With the can upside down you're sending liquid down into the system and using body heat to create vapor/pressure to push it in. Getting a pan of warm water is more trouble than it's worth especially of you don't have that much hose to reach the connector and the pan. Better off paying attention to the gauge than trying to balance that pan of water.

 

Ok, over the weekend I added some 134a with no luck. Went from 45psi up to about 55psi on the low pressure port. Let the car run for about 30 minutes with a A/C cranked up and the compressor still turns on for about 4 or 5 seconds then turns off. Any other suggestions?

 

My guess would be that you have a compressor clutch shim problem.

 

To be sure you should run a wire from the positive battery post directly to the compressor clutch wire. This will bypass any and all pressure switches etc. and energize the clutch directly. Have the fan on high and your gauge attached. The wire you need to access is one that comes directly from the back of the clutch and goes to a clearish rubber connector in a clamp on top of the compressor. If you touch that wire to the one from the battery you should hear the clutch click in and out. Start the car, fan on high, gauge attached and connect the wire.
Does it get cold? What pressure do you have. If it drops and the clutch is still engaged add more freon. If the pressure is high (55 like you said) and not cold, bad compressor or bad clutch ???