2009 XC70 Desiccant Bag Replacement

[tancookbelle]

Purpose:

To show how to replace a desiccant bag which created a blockage in an AC system on a 2009 Volvo XC70. (This is applicable to many Volvos 2007+ and Landrover LR2
.
Background:

I have a 2009 XC70 3.2 with 196000 km. I went to use AC for first time since winter and it would not blow cool air. The compressor also made a whining noise when the clutch was engaged and the pitch changed with engine speed. I placed a gage on the LP side and found the pressure to be approximately 55 psi with the engine stopped. I started the engine and the compressor pull a vacuum on the system which indicated to me that there was a blockage. After looking at the AC circuit design I concluded that I had either a block thermal expansion valve or an exploded desiccant bag. I had the gas removed and the following describes the repair. It is noted that desiccant bag was only plugged and the fix was low cost.

Repair

First I needed to verify where the blockage was located. I removed both AC hoses at the compressor. I then opened the HP piping connection on passenger side in front of radiator expansion tank.

Using an air hose I blew air thru LP hose at compressor and air came out at HP pipe connection indicating thermal expansion valve was OK. I then blew air into HP hose at compressor and nothing came out at HP pipe connection, which indicated a blockage in the condenser. I first reconnected both compressor hoses and then the HP hose. I Googled desiccant bag failures and did not like what I saw. Failed bag with desiccant thru the system. This caused me to take the condenser out of car which in hindsight I did not need to do. Further on you will see I only needed to replace the bag.

I put the car up on ramps and removed the plastic panel in way of the oil pan. I then removed the plastic panel attached to the bumper (three plastic clips, 10 screws)

The last removal will be the four bolts for the metal cross-member that supports the radiator, condenser and oil cooler. Before you remove the bolts release the ¼” vent pipe from its bracket on passenger side of radiator. This pipe sees to much strain when you release the radiator support bracket.

At this point you should you removed the plastic plug (T-70 Torq) from the driver side of condenser which houses the desiccant bag. Below is a picture of the old and new bag and plug showing the blockage.

Install the new bag (3076238) and plug (30776239) and then reassemble everything.

Once everything is back together you will need to pull a vacuum on the system for an hour to remove any moisture in the systems. I purchased a vacuum pump that also came with AC gages (FJC KIT6 from Amazon).

At this point you are ready to recharge the systems with R-134A (0.8kg).

In my case I refilled the system with a product called R12A RedTek available in Canada at various repair locations. The two six ounce bottles and changing hose cost $58. My only problem was that I overcharge the system trying to install the 10.5 ounces of R12A recommended by the manufacture. The LP pressure went to 70 PSI and caused the compressor to make a very noticeable whining noise. Once I reduced the LP pressure to 30-38 psi; also a manufacture recommendation; the whining noise was gone and it was blowing cool air again (14C vent on a 28C day).

Summary

If your 2007+ Volvo AC system experiences no cooling, compressor whining and the LP side pulls a vacuum then you probably have a desiccant bag causing a blckage. Have the gas removed in accordance with environmental regulation. You can probably do the repair yourself and then have the system recharged making cold air once again.

[toma nova]

Great write up! What was the cost for parts and to pull the old refrigerant?

Does anyone know if this is a preventative maintenance item? We run climate control in auto year round, so the a/c is cycling all the time (extremely humid in Houston most of the year). That old desiccant bag looks nasty - I may pre-emptively replace ours.

Thanks,
Tom

[tancookbelle]

The desiccant bag and plug cost $30 and gas removal one hours shop time. The replacement will take about two hours. The vacuum pump and gage set cost $230. The vacuum pump was run for one hour to de-hydrate system. In the USA R134a is available from auto parts store thus you can re-fill yourself. Make sure you add the correct amount by weight slowly and do not over fill system.

[slayer8870]

Great job tancookbelle - very impressive DIY!!!
I have one question:
You are mentioning that your compressor was doing whining noise, which changes along with the engine RPM...I have the same problem, but mine A/C works fine - just wondering could it be due to the level/pressure of refrigerant in the system? and just refilling the system might address the noise issue?
Thanks in advance.

[tancookbelle]

There is a Volvo service bulletin concerning lowering the refrigerant level on 2008+ vehicles if requested by the customer based on a compressor whining noise. The 2008+ A/C compressor is a variable displacement design that seem to exhibit a whining noise issue if the HP pressure is too high. I overfilled my A/C system during the repair and got the whining noise. When I reduced the pressure to LP 36 psi and HP 170 psi on a 24C degree day the noise went away and has not returned. You will note that because the compressor is variable displacement it does not cycle the clutch on/off with the engine at idle which how older fixed displacement compressors function.

There are also other reasons for whining noise such as compressor clutch bearing, compressor internal bearing or belt idler bearing. I would first turn the A/C system off. If the whine remains then it is either the belt idler bearing or a compressor clutch bearing. If the whining stops then problem is with the A/C side and I would look at checking the HP/LP pressures and lowering the LP pressure to no higher than 40 psi on a 25C degree day. Finally the power steering pump is near the AC compressor and will also make a whining noise if starting to get low on fluid.

[slayer8870]

Good thing you mentioned the lowering of the pressure. I tried to do it under VIDA. There is a setting under the CCM (Climate Control Module) that says the following:
================================================== ================================================== ===================
Programming the evaporator, climate control module (CCM)
Programming
Note! This adjustment must only be carried out on the vehicle if the owner requests it.
The noise from the compressor can be reduced by reducing the level in the evaporator.

In order for this change to be possible on model years up to and including 2008, the latest software must be downloaded to the Climate control module (CCM).

Note! This programming is only possible on vehicles with more than 4 cylinders.
================================================== ================================================== ===================


It did not seem to work for me. Noise is there no matter if you have high volume or low in the evaporator. I think it must be the pressure as you've said, because once I turn off the A/C the noise goes away.
BTW do you need any special tool to check LP/HP levels? It seems that I don't have these reading under VIDA, so I guess I have to plug in some pressure gauge into the system...
Thank you very much for the detailed advise.

Kiril

[tancookbelle]

I purchased A/C gauges complete with the quick disconnects on Amazon as shown in the second photo below. When you attach gauges on a cold system not running you should ready approximately 70 psi on a 24C on both gauges. Both my 2001 V40 and 2009 XC70 read the same R134a pressures with the AC system stopped. Start the car and let it run for five minutes. Record the LP and HP pressure and outside temperature. You need to look in R134a table to see what is a normal HP/LP pressures for an outside temperature

[slayer8870]

I am bit lost here...if you can help me that would be great
So where do you find the recommended LP/HP numbers for the car A/C system?
If I look in a R123A property table (one for example here: http://www.ohio.edu/mechanical/therm..._TempSat2.html) it says that if the outside temperature is 24C then the nominal gas pressure would be 645.8 or ~94 psi. With that said how can you tell that LP has to be 36 psi and HP 170 psi as you mentioned in your previous posts? Is this something that comes from Volvo, or it is a trial-and-error approach?
Thanks in advance for your great information!

Kiril

[ssicarman]

R-12 had a wonderful pressure to temperature relationship. Sadly it also had a way with destroying the ozone layer. At 70 degrees F the pressure in a static system the pressure is 70n PSI. At 100 degrees the pressure was 100.
R-134 does not have that direct temp pressure relationship but it is close. So at 70 degrees the pressure in a static system should be around 70 PSI.
It is nice to know info but limited use.

With the system operating the pressures can be different under different temperature and humidity conditions, they affect the load on the system. General rule of thumb for most AC systems is the low side should be 30-40 PSI and the high side shouldn't really be much more than 250 PSI. Each manufacturer should have a table showing what they expect the system pressures should be at X RPM's, X temp and X humidity.

[slayer8870]

so to give you an update - I bought a pair of A/C gauges and plugged them over the weekend to the A/C of the car. Outside temperature was 29C with low humidity and the static pressure in the system was 116 psi on the LP and 105 on the HP side. That is within the limits of the thermobaric properties of R134a - according to the thermal table it should be around 108 -110 psi. Then I started the engine and run for about 30 min. At idle engine which is 700 rpm I recorded 38 psi at LP and 180 psi at HP. At 1500 rpm LP wend down a bit to 28 psi and high did not change - 180 psi. I did observe the pressures at different RPMs and none of the ends tent to go over or under these proposed zones.
From the analysis it seems that the A/C system is good pressure-wise...Everything is within the limits. I went ahead and tested the A/C temperate at the inside vents according to Vida, which btw dictates that if ambient temperature is 30C the air coming out of the central vents inside the car has to be 10-14C. I recorded even 8C at some stage. So long story shorts - the compressors continue to whine along with the RPM of the engine and it seems now that it is the problem itself. For now I am abandoning this project, because A/C works fine and I don't see an immediate need to replace A/C compressor given the fact that the whining is noticed only by me - the wife didn't even bother to try and hear it :-)
Thanks for your support. It was a great technical exercise for me to dig in deeper into the car A/C system.

Kiril