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2008 XC90 V8 AC problems

Help, Advice, Owners' Discussion and DIY Tutorials on Volvo XC90s. The XC90 proved to be very popular, and very good for Volvo's sales numbers, since its introduction in model year 2003 (North America).
shaneb
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2008 XC90 V8 AC problems

Post by shaneb » Sun Aug 05, 2018 5:07 pm

New to the forum, been lurking for a while.
On the list of things I am working on, on our 2008 XC90 V8 we purchased a little over a year ago is the AC not working as well as I believe it should.

With manifold gauges I am getting up to 55 Low but only 150-200 Hi side. It never blows much better than 59 or 60 in 90-100 degree weather. Rarely that well. Also experienced the 10-15 min issue in cooler weather where it wouldn't even blow that cold of air when you start the vehicle.
I recently got VIDA working.

I get a EVAP temp of 60 degrees, and the pressure is reading very similar to my gauges at about 150 on the hi side.
I have seen others reference Compressor Duty as a point of data in VIDA but I have looked under all the control modules (ECM, CCM) and cannot find a data point that seems to relate to the compressors valve position or how much it is supposedly engaged.

Is there a value in Vida that will tell me what the compressor is actually trying to do?

I have a new solenoid control valve on hand, and I have a receiver/drier coming. I plan to swap those out because from all the searching that seems to be the common issue.
I would like a way to measure this when I'm done replacing, so i can actually compare results with old/new parts.

Ideas?



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oragex
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Re: 2008 XC90 V8 AC problems

Post by oragex » Sun Aug 05, 2018 5:15 pm

Welcome.

200psi high is actually a little bit too much. Even the 50 low side is actually too much, maybe overfilled by a previous owner? The compressor will work too hard and may not be efficient. I'd try removing until it stays at no more than 35 on the low side.

Also, I'm assuming the radiator fan kicks in at low speed when the a/c runs ?



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Re: 2008 XC90 V8 AC problems

Post by shaneb » Sun Aug 05, 2018 7:08 pm

I have tried evacuating some. If it is any lower than it is right now, the discharge temps and EVAP goes up to 80ish.
I did not evacuate it below 45 or so though. Are you saying if I go further it will get better after it gets worse as it releases?

The reason I assume 200 is low for the HI side is that each 134A chart I can find, at these ambient temps, should be well above 200, as high as 330 on the extreme? I am talking 95-105 ambient temps at time of measuring.

Do you have a reference for what the HI and LO should be at ambient temp? I'm all about learning what it should be if my charts are wrong.

Thanks in advance



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Re: 2008 XC90 V8 AC problems

Post by oragex » Tue Aug 07, 2018 4:25 am

These guys seem to say that high pressure would be somewhere between 150-200 (hot, humid day, perhaps some 90F or more) at around 27:30 in the video www.youtube.com/watch?v=xBuAQuWezMY

I just don't get why with this pressure it cools this little. Don't think there's a blockage as the pressure balance between low and high seems fine. Maybe there's air in the refrigerant? Is the radiator fan spinning - it should spin to cool down the condenser.



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Re: 2008 XC90 V8 AC problems

Post by jimmy57 » Tue Aug 07, 2018 7:37 am

All V8 XC90s have variable displacement compressors. There is a solenoid on the compressor to control the displacement that is operated by the ECM. The solenoids do fail and the compressor can have no pumping or less than full pumping when the solenoid binds and does regulated pressure in compressor crankcase. Often the solenoids will not function until the engine warming up heats the compressor and the solenoid expands and the armature no longer binds in the bore.

The solenoid can be replaced but on a V8 with higher mileage it may be wiser to replace compressor.

High side pressure is temp, humidity, and engine speed dependent. If you elevate engine speed according to std a/c diagnostic procedures (1200-1500RPM, fan speed 1 less than full, recirculation selected) you will see almost 300 psi on a perfectly working system initially on hotter and/or humid days until interior temp falls. System with two evaporators will have higher high side pressure also. Of course, blocked airflow through condenser or condenser fan problems make the high side pressure high when it shouldn't be. Once the car cools down the 30/180 for the pressures would be good targets. On a vehicle with variable compressor the pressures will not abide by the chart too well. The compressors used in this arrangement often have a bit more capacity so at idle speed with 100% solenoid activity the a/c will be better. Compressor capacity falls off below 1200 RPM and that is why so many cars have poor a/c in stop n go traffic or if sitting still idling. When the interior temp cools (as measured by evaporator discharge air temp sensor) the ECM will decrease the compressor solenoid signal % and the compressor will lose pumping capacity. On a well cooled vehicle with fan speed lowered the lo/hi pressures can be 48/150. The evaporator temp is prevented from falling below 3C-5C to avoid having evaporator freeze.

The evaporator temp probes are reliable but do fail but it is rare.
Your listing of it not cooling at all for 10 min on some occasions puts you squarely in the solenoid sticking category as that is a hallmark failure for the solenoid.
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Re: 2008 XC90 V8 AC problems

Post by wanderdüne » Tue Aug 07, 2018 8:38 am

Given recent experience with my a/c, which turned out to be overfilled by the previous owner; I would highly suggest that it is worth the fifty bucks to have a professional diagnose a/c problems, even if the repair or replacement is done by you. Any shop like a Tunex is going to have sophisticated equipment and experience to do a proper and rapid diagnosis. Leave this to the pros. That's my opinion.

Eric The Car Guy video on the topic:
Last edited by wanderdüne on Tue Aug 07, 2018 8:53 am, edited 1 time in total.



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Re: 2008 XC90 V8 AC problems

Post by abscate » Tue Aug 07, 2018 8:41 am

With a new-to-you vehicle it is easy to be a victim of a top-off-er, who 'puts a can in' every once in a while to fix a leak, which is now overcharged.

If AC is mission critical to you, which Im guessing it is in TX, evacuate it for 2 hours, charge by weight, then evaluate performance.

Hold off on the receiver until you decide if you need a new compressor or evap, or both


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Re: 2008 XC90 V8 AC problems

Post by shaneb » Tue Aug 07, 2018 11:39 am

@jimmy57 - Thank you. Your expectations are similar to what I thought I should be seeing. Car has like 140,000 on it, and though I may be replacing the compressor sometime in the near future, the 120 dollar valve (given the abundance of others having the issue) seemed like a simpler (cheaper) first go. In cooler weather, (when the "resting" temp of the vehicle isn't already 115) I noticed the delayed cooling issue described.

@abscate - Thank you. I had already ordered the valve, too late to return. And I was about to install it but decided to listen to everyone saying you should replace the receiver too? If that isn't really necessary, I will send it back.
I agree with your opinion on the evac - there is just NO way to know for sure unless it is re-filled with the appropriate known weight...all this guessing on "is it overcharged, is it undercharged, is compressor valve stuck" starts to make me crazy when that is always in the back of my head.

If i evacuate, I will go ahead with the valve as it seems simple enough while the system is empty.
Do I have to (or should I) do the receiver as well before refilling and testing with proper charge? Better to just do it all while its empty. Or you would just do the recharge by weight before replacing anything?

Thanks again



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Re: 2008 XC90 V8 AC problems

Post by abscate » Tue Aug 07, 2018 12:15 pm

Volvo recommendation on the models I work on (not the XC90) is drier replacement is recommended for a blown system or one open to air for more than 24 hours.

The internet tends to bleat that you should replace it whenever you crack the system, but thats because people love to spend others' money.

You should be able to find an AC shop that will evacuate your system for free or low cost. Then each fill costs you about $10. Almost nothing. If you fill it to spec by weight and don't get good performance, then you know you need more.
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Re: 2008 XC90 V8 AC problems

Post by jimmy57 » Tue Aug 07, 2018 2:37 pm

The receiver/drier replacement is recommended but if you replace the valve the system will still be outgassing if you drain system immediately prior to pulling out the valve and replacing it. That would make the amount of moisture intrusion minimal and there should be no issues with not changing the receiver/drier. Add some refrigerant oil to system either with injector or an oil charge can.



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