AC not blowing cold

Hopefully this is the last issue I have to face on this dang car for awhile.

Just did a new turbo and now the AC isn't blowing cold.

2006 Beetle TDI with DSG. 135,000 miles.

Compressor clutch is kicking in and both fans on the condenser/radiator are working.

Pressures with AC off:
High:120
Low: 120
Pressures with AC on:
High: 150
Low: 75

When the compressor kicks on, the Low drops to around 65, moves up to 79, and then settles to 75. This takes about 10 seconds total and about 3 seconds for the drop from 120 to 65.

Should I just go straight for a new compressor and dryer or is there some other things I can do to try and narrow this down to a different issue?

THANKS!!!

Refrigerant Control Valve (RCV).

Pressure on the low side should be no less than 35 psi up to about 45 psi with the high side 175 psi or higher, depending on ambient temp, etc.

I'm not sure if the RCV is an internal mechanical or an external electrically controlled on your vehicle. If there is more than one electrical connection on the AC compressor, well it would be the latter.

To replace the mechanical RCV requires disassembling the compressor to access...

Andy,

Very much appreciate the reply. I’ll look into this valve.

Thanks!

AndyBees said:

Refrigerant Control Valve (RCV).

Pressure on the low side should be no less than 35 psi up to about 45 psi with the high side 175 psi or higher, depending on ambient temp, etc.

I'm not sure if the RCV is an internal mechanical or an external electrically controlled on your vehicle. If there is more than one electrical connection on the AC compressor, well it would be the latter.

To replace the mechanical RCV requires disassembling the compressor to access...

Click to expand...

I thought to replace the valve you need to discharge the system, remove the valve from the end of the compressor, reinstall the new one, recharge the freon. Disassembling not needed.

Suck and blow.

The compressors job is to SUCK the low side down (brings the approximate charge of 70 psi down to 30-40), and BLOW more pressure into the high side (pressurize the approximate 70 psi up to much more depending on ambient)

If the low side isn't low enough and the high side isn't high enough then the compressor isn't sucking and blowing good enough. But, mk4 compressors have a Refridgerant control valve (RCV) as others have mentioned, and its job is to regulate low to high side, so if compressor isn't doing its job, then a RCV will probably fix it. What happens is the valve sticks allowing high side pressure to leak into the low side.

Only complication is you don't really know the condition of the compressor but you should try the RCV. Freon will need to be evacuated and compressor will need to be removed and disassembled to replace the RCV.

On the mkiv’s you have to disassemble the compressor but I don’t think you have to on mk5’s. Still have to r&r freon.

The SD 7V16 AC compressor that come on MK4s has an internal mechanical RCV that is not accessible from the outside. Yes, the refrigerant has to be evacuated and disassembly of the unit is required to remove and replace the RCV. The mechanical RCV is pressure operated vs a semi-external RCV which is electronically operated.

As I alluded to previously, I am not familiar with the AC compressor that come on the MK5s.

Below are some pics of an RCV in the SD 7V16 AC Compressor. (I'm sure many of you have seen these pics.)



Below is the RCV. The nut is used to bolt it to the reed valve assembly.



Below you can see the reed valve assembly and the hole in the center where the RCV goes.



Below, you can see that I replaced the RCV with a bolt and nut. This makes the compressor a fixed displacement unit which I am using on the ALH in my Vanagon.



Lastly, the purpose of the RCV is to allow a controlled flow of refrigerant to constantly be circulated providing a continuous flow of cool air from the vents without the AC compressor kicking On and Off. The RCVs action of bleeding refrigerant internal to the housing changes the displacement of the compressor (affects the angle of the swash plate). In a nut shell, once the AC is turned On, the AC Compressor never cycles Off and On. So, if the RCV begins to malfunction, as CoolAirVW alluded, well, the system won't cool properly! I've seen them work just fine one day and not the next, etc., or right before my eyes with Manifold Gauges set up watching it misbehave!

Hope this helps!

AndyBees said:

I've seen them work just fine one day and not the next, etc., or right before my eyes with Manifold Gauges set up watching it misbehave!

Click to expand...

I had one that was NOT working and started working right before my eyes (watching gauges on AC machine). I was "training" my employee and we both saw the pressures (higher than normal on low side and lower than normal on high side) then both high ad low side the needles flicker erratically then jump to normal pressures on both high and low side.

We have replaced bunches of RCVs on mk4, and its been successful everytime. But you still always wonder if the compressor is ok or not.

Did RCV on friday, and made a video about it. It was on a 2.0L gas but 1.9L ALH compressor is the same compressor and removal is even easier, from the bottom.

https://www.youtube.com/watch?v=qtrXyrHfScM

CoolAirVw ........... awesome! Fantastic !

I love photos and YouTubes! They remove most doubts and questions. A visual is great for filling in all the perceived missing pieces! Thanks for posting!

Question/comments..

Pressures are affected by temperature and volume of refrigerant in the system (not enough or too much). Do you measure (weigh) the volume or just go by the sticker spec? I've noticed on some vehicles the sticker spec has a + or - that is almost a 10% swing up/down.

I ask and comment because with my Vanagon, I have no clue what the required amount of R134a is necessary for optimum cooling. So, I just add refrigerant until the high side pressure is about 275 psi with ambient temp in the range of 78 to 85f (low side 35 to 45 psi). Also, I use a box fan out front of van to add extra air. With this scenario, I'm getting temps in the low 40s out of the vents. Generally, it takes slightly more than two 12 ounce cans to achieve these numbers. What's your thoughts on those pressure ranges?

That's a great video. Does the RCV come with the gasket kit too?

AndyBees said:

CoolAirVw ........... awesome! Fantastic !

I love photos and YouTubes! They remove most doubts and questions. A visual is great for filling in all the perceived missing pieces! Thanks for posting!

Click to expand...

Thanks so much. All I get for making these videos is a thank you every once in awhile. I get some negative comments too, which is ok, I understand its the internet.

AndyBees said:

Question/comments..

Pressures are affected by temperature and volume of refrigerant in the system (not enough or too much). Do you measure (weigh) the volume or just go by the sticker spec? I've noticed on some vehicles the sticker spec has a + or - that is almost a 10% swing up/down.

I ask and comment because with my Vanagon, I have no clue what the required amount of R134a is necessary for optimum cooling. So, I just add refrigerant until the high side pressure is about 275 psi with ambient temp in the range of 78 to 85f (low side 35 to 45 psi). Also, I use a box fan out front of van to add extra air. With this scenario, I'm getting temps in the low 40s out of the vents. Generally, it takes slightly more than two 12 ounce cans to achieve these numbers. What's your thoughts on those pressure ranges?

Click to expand...

I like your pressures, but honestly it would be best to find a weight spec and have someone put the exact quantity in that it requires, but I'll bet yours leaks a bit, and then you would have to have them do it every year, so if yours is working fine I guess if it ain't broke then don't fix it. On most systems the way your doing it is accurate enough. Obviously if your getting 40 degrees out of the vents then its probably just fine.

AC machines are required by law for a shop to service AC systems. Those machines weigh the freon and that is the only way to accurately know the quantity. So of course we add based on weight.

I tried to look up how much freon your Vanagon would take but its too old and my tech service info doesn't show it. Maybe your Bentley would?

I would assume that yours originally was a R12 system? How did you convert? I had a discussion with a customer regarding his plans to upgrade his system and this is what we came up with.
1. Upgrade rubber hoses to solid lines where possible (under van) to slow down "yearly leaks". And of course replace the rubber hoses that are necessary.
2. Upgrade to a compatible condenser for R134 since there is major design difference from R12 and R134 there that could hinder performance.
3. Fabricate rear air system.
4. Upgrade to a modern compressor, whether aftermarket or from a later vehicle (Caravan or a big Suv) with rear air.
5. Tint windows to keep the sun out.

We never did this but would be excellent to see someone who did.

jokila said:

That's a great video. Does the RCV come with the gasket kit too?

Click to expand...

No, but you can order from same place (polar bear)

Well, I suppose we've hi-jacked the OP's Thread ... I do apologize, but there is some good info here.

CoolAirVw, here are the things I've done to the AC in my Vanagon.

1. Replaced the rubber hoses and O-rings
2. Flushed the Condenser and Evaporator
3. Installed a new accumulator/dryer
4. New expansion valve
5. Modified the SD 7V16 compressor as shown in the pics (4 ounces of oil in compressor)
6. During charging I added 5 ounces of oil

I did the above last July after years of leaks and breakdowns. I had no choice but to replace the hoses (coldhose.com). So, while into it, I did the flush. Previously, I had removed the evaporator and gave it a good cleaning on the outside (lots of lint).

Anyway, it would hold 29 plus inches of vacuum when I finished.

After two cans of refrigerant, from there it's all but impossible with my manifold gauges to determine the amount I've installed, unless I can put in a complete third can.

Well, since it is cooling, I'm leaving it alone.

AndyBees said:

After two cans of refrigerant, from there it's all but impossible with my manifold gauges to determine the amount I've installed, unless I can put in a complete third can.

Click to expand...

I did find a spec on how much for your Vanagon. It's in a booklet put out by "Murry climate control" that shows most makes and models freon type and capacity and oil type and capacity. Murry makes AC parts that are sold by Oreilly auto parts and other auto parts stores. I've made comparisons between this booklet, my tech service, and the AC sticker on the cars that I service and it has been accurate except for one Toyota.

It says.....

89-91 Vanagon All engines 51 oz R12, 8.oz mineral oil

CoolAirVW...thanks for the video. I was looking all over youtube for something like that.

I pulled the compressor yesterday and the insides and oil look perfect. I'll be placing an order with PolarBear today and see if I can get this fixed next weekend.

Should flush the whole system and start with new oil? I captured all of the oil I could from the compressor. I assume I'll lose some when replacing the dryer too?

Thanks again to everyone!

wmcclendon said:

CoolAirVW...thanks for the video. I was looking all over youtube for something like that.

I pulled the compressor yesterday and the insides and oil look perfect. I'll be placing an order with PolarBear today and see if I can get this fixed next weekend.

Should flush the whole system and start with new oil? I captured all of the oil I could from the compressor. I assume I'll lose some when replacing the dryer too?

Thanks again to everyone!

Click to expand...

if you didn't have a "metal failure" then no flushing required. Honestly I dont know how effective any type of flushing is anyway.

Replacing the drier is always a good thing, just measure the amount of oil that comes out and install that amount. Of course do the same with whatever oil came out of the compressor.

I flushed (and flushed and flushed) the evaporator and condenser in my 34 year old Vanagon when I was replacing the hoses. The liquid that come out was only slightly discolored (no metal or chunks of anything).

I'd say I wasted my time and cash. As CoolAirVw said, unless the compressor failed resulting in metal particles, flushing is most likely not necessary. And, as he suggested, replace the dryer and add the correct amount of oil.

My Vanagon has the ALH with the SD 7V16 compressor. Seems I come to the conclusion that my system needed 8 ounces of oil........ 4 in the compressor and the balance out in the system. I may have induced 9 or 10... anyway, it works fine! A smidge over is not going to hurt anything. I'd rather be a bit over than under with oil.

Got everything put back together Sunday and charged up and I have COLD AIR!!!!

Extra thanks to everyone here for the help. The pictures and videos really helped out a lot.

Now to get the rear brake pads done and hopefully not touch this car again for a long time!

round of applause for another vehicle fixed and another tdi kept working good!