2003 Volkswagen Eurovan AC Troubleshooting

[davevw]

Hello Everybody-

Joined because I'm trying to troubleshoot the AC system in this Eurovan I just bought. At some point, I also plan to install AC in my 1978 Bus, so I kind of figure this will be good practice. Anyway...

Seller told me he stopped driving the van last summer when both the driver side window stopped working (hopefully that is soon to be fixed!) and the AC also stopped working. He said that Midas told him they thought the AC compressor clutch was bad and that was the problem. It is indeed rattly when not engaged and the arms appear to be a bit worn out. However, I don't think this is the issue with the system as a whole because the clutch is engaging. If I can get the whole system operating and just replace the clutch, that would be my preference. Since the clutch is still working to some degree, I figure I can test the other stuff-seems like it is either on or off, not like it could be "slipping," right? Anyway, here is what I found yesterday: The radiator fans do turn on, and the AC clutch does click on and engage. It was in the neighborhood of 65-70 degrees outside while I was working on it. At idle: I get slight cooling inside the van, but definitely not cold air. The low side pipes don't really feel cold in the engine compartment. Pressures: Low side 54 PSI, high side 145 PSI. At 2,000 RPM: The cooling goes away. Pressures: Low side 85 PSI, high side 100 PSI. This system has dual evaporators. So I wasn't sure if the pressures should be higher than what the general ranges on the DIY can gauge I started out with. (It showed the 54 PSI to be too high, so I switched out to my more precise gauge.)

[davevw]

I found this chart for the van on ALLDATA. Does this indicate that perhaps the low side pressure at about 70 degrees ambient temp should be about 68 PSI? (Indicating I should add a bit of refrigerant and see what happens?


Temperature/pressure relationship
R-134a in an enclosed container will have a specific temperature/pressure relationship.

Temperature in °C (°F)

Pressure in bar (psi)

-30 (-22)	0.0 (0.0)
-20 (-4)	0.3 (4.4)
-10 (14)	1.0 (14.5)
0 (32)	1.9 (27.5)
10 (50)	3.1 (45.0)
20 (68)	4.7 (68.2)
30 (86)	6.7 (97.2)
40 (104)	9.1 (132.0)
50 (122)	12.2 (177.0)
60 (140)	15.8 (229.2)
70 (158)	20.2 (293.0)

[Cornbinder89]

Yeah, you got some problems going on there. The low side pressures are way too high and the high side are low. It is going to be way more than a clutch problem.
I don't know where I would start with it, not knowing what equipment you have. I'd be inclined to pull the compressor check how much oil is in it and replace the oil with new, while making sure it can compress holding a thumb over the outlet while turning the crankshaft. This assumes is a normal compressor (clutch is an indicator that it is) an not a variable displacement type. If it passes the "thumb test", re install and evacuate the system, recharge with the correct amount by weight and see where you are.
The high low side doesn't point to a mere "low of refrigerant" problem, more likely air in the system or other problems..

[davevw]

The chart here seems to indicate the same thing to me. I'm just curious why I also see a lot of things kind of generally say shoot for about 35 PSI on the low side.

https://forum.aircondition.com/forum...pressure-chart

[davevw]

Again, the system has dual evaporators, with one in the front in the dash per usual, and a second way back in the back. I'm just unsure if that makes a difference on what pressure to look for on the low side. I did see an indication someplace that you did need higher low-side pressures for dual evaporator systems.

That ALLDATA chart seems to make it look like at 68 degrees F (that is always just the outdoors temp) I want to see about 68 PSI. Unfortunately, ALLDATA doesn't indicate if that is high or low side, or engine running or not.

[Cornbinder89]

I'm not sure what your asking. With the system off, with some refrigerant in it, having sat with the engine not running for a long time, the static pressure of the system should equate to the pressure on the chart for that temp. Running is different. The high side pressure equates to the condensing temp of the refrigerant in the condenser , the low side should indicate the boiling temp in the evaporator

[Cornbinder89]

OK, Lets get really basic here. YOU CANNOT TELL THE AMOUNT OF CHARGE FROM THE PRESSURE. It can tell you if it is way off, but not by how much.

[davevw]

I'm not sure what your asking. With the system off, with some refrigerant in it, having sat with the engine not running for a long time, the static pressure of the system should equate to the pressure on the chart for that temp. Running is different. The high side pressure equates to the condensing temp of the refrigerant in the condenser , the low side should indicate the boiling temp in the evaporator

Ok, this makes sense. I'm somewhat basic in my in-depth knowledge of AC systems. I know just enough to be dangerous! ha.

[Cornbinder89]

Ok, I am going to say something you're not likely going to want to hear, but from your questions I can tell you don't even have the basic understanding of compression cycle refrigeration. It doesn't seam you have a handle on phase charge of refrigerants, and this is very basic to have a handle on.
If you want to learn, it is not something easily taught over the internet. I would suggest that you try and find someone local that can teach you the basics, help diagnose the problem you have and show you how to work SAFELY with refrigerants. You can blind yourself by getting high pressure liquid in your eye and frost burn if it gets on your skin. These are real dangers.

[davevw]

OK, Lets get really basic here. YOU CANNOT TELL THE AMOUNT OF CHARGE FROM THE PRESSURE. It can tell you if it is way off, but not by how much.

I understand I cannot tell how much refrigerant is in the system at this moment by the pressures.

What I was thinking of initially trying was getting one of the DIY kits at the FLAPS, hooking it up, and adding refrigerant to see if topping it off would help. It just seemed like being low was the most likely cause of only working a bit-with very little cooling.

When I hooked up the DIY gauge, I saw the needle was in the "yellow" zone at about 55 PSI. That's when I broke out my more precise gauge and took readings at the high and low side.

So I know that in a car, with a car sized system, on a hot day you want to see around 40 PSI on the low side.

What I'm curious about is if the fact that my van has a big ole van-size system with two evaporators means I actually want to see a higher pressure on the low side? Or is it pressure is pressure is pressure so that means always about 40 PSI?

[Cornbinder89]

Pressure = temp at the point it is measured, period! Duel evaporators can effect how well the system handles the heat load, but again, pressure = temp at the point measured.
Alot can depend on how the system is designed. Does it have dual Tx valves, A Tx and orifice tube, variable displacement compressor etc.
Air or other non-condensable gases will throw pressures off. Moisture creates other problems.
Pressure for a given refrigerant doesn't change with the size system.

[davevw]

I appreciate you taking the time to answer my questions. I do understand the theory and principals behind how AC works, as well as the safety issues. But like I said, I'm a bit of a beginner with it and still learning some of the lingo. I've done a lot of shade tree stuff for a long time, to include some VERY basic AC stuff, but this is getting further into it than I have yet to do. (I'm excited to have the chance to build upon the knowledge I do have and learn more!)

Here's a pic where you can see the expansion valve(s) on the right side of the pic. Edit: I did confirm that there are two expansion valves in the Van, one at the front (pictured here, and you can see where the lines Y off to the rear evaporator) and one in the back at it's evaporator.

As you said, I do not believe it is a variable displacement compressor; I don't think VW went to those for a few more years after this was built.

[nickyanc]

I have worked on these vans before,don't know the LHD version but I assume they have the same Sanden compressor and to me it looks like you have a compressor problem. Assuming that you have checked the 13mm nut at the front of the compressor shaft is spinning together with the clutch plate when it's engaged (making sure you don't have stripped splines on the compressor shaft) then you have a faulty mechanical pressure control valve inside the compressor. I have replaced quite a few of these mechanical control valves over the years it's not too hard if you know what are you doing but otherwise you need to replace the compressor and I would fit a new R drier too.Check the oil inside your compressor and if it's black and muddy than flush the system,if you post a picture of the compressor I would be able to tell you if it's the one with built in mechanical control valve.

[davevw]

[davevw]

[davevw]

Hopefully those pics help identify the compressor and type. If it helps with identification, the center nut on the clutch is 14mm. As you can see in those pics, the clutch's "arms" are clearly broken and worn out, but it does still seem to be "clutching" for the moment.

FWIW, I checked pressures the other day prior to turning the engine on (it'd been sitting for a few days) and the pressures on both sides were reading equal and correct for the ambient temp. So I guess that at least means I'm not over-pressured?

Also, the temp in the rear AC wasn't blowing cold yesterday either. I was thinking that if the problem was the front expansion valve, then perhaps the rear valve was working OK and it'd blow cold despite the front not blowing cold. Perhaps I'm way off on that assumption.

I'm thinking that since obviously the clutch needs replaced, I might as well replace the whole compressor, along with the dryer, and just flush the lines to ensure I'm starting with fresh system innards.

On a VW website, I saw a post where they espoused running an AC flush chemical through the system, then filling the system with nitrogen to remove all air, then pull the vacuum, and finally then fill. Thoughts on this approach?

[nickyanc]

That compressor is the one with mechanical pressure regulator inside Remove the compressor (degas and recover gas first) and check oil, if oil is nice and clean do the oil balance with the new compressor (leave @20ml extra in the new compressor due to dryer replacement ) run the system at least 1/2 hr with the vacuum pump (this way you are getting read of the air and moisture inside ) and regas the system. if the oil is black than you have to do a manual system flush

[davevw]

That sounds like a plan. By "oil balance" I want to make sure I understand what you mean.

Are you saying measure what comes out of the old compressor, and measure what is in the new compressor, and then adjust the amount of oil that is in the new compressor to match what I poured out of the old one, plus 20ml of oil to compensate for an approximation of what will be lost by replacing the dryer? And that 20ml would just be added to the new compressor, yes?

[davevw]

Also, are you saying that the nitrogen "flush" the person recommended is unnecessary since I will be pulling the vacuum?

[davevw]

Finally (maybe...) I found this kit. Seems like a decent deal to get all that stuff. But do you think it is worthwhile buying a second expansion valve and replacing the one at the back at the same time? Looks like only one is included.

https://www.buyautoparts.com/buynow/...xoCmmkQAvD_BwE