ALH AC Compressor Help

markward

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Jul 5, 2007
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82 Vanagon and 2011 JSW
This is sort of a cross post. I have the aftermarket AC system installed into my Vanagon. It is an aftermarket vintage air unit. I was not exactly happy with the vent temperatures and decided to dig into it further. I am using the Sanden SD7 V16 compressor that came stock in the New Beetle TDI. The low side does not seem low enough. The high side is also lower than it should be. I contacted tech support at vintage air and we went through the usual suspects and in the end determined the problem maybe that the compressor is not compatible with the vintage air system. He was not familiar with this compressor, but said it will not work with a variable displacement compressor. The expansion valve is not compatible. The Vintage Air unit uses a old style expansion valve. The type that looks like a mushroom. Needless to say I am bummed. They say the fix is to install a fixed rate compressor. That means I am going to have to figure out a way to adapt one to the factory bracket. It looks like the New Beetle used an H type of expansion valve. Not looking for a lecture, but if you have some experience with this, I would appreciate it. I don't have a lot of experience with this type of compressor. The reading I have done says it is a variable displacement compressor, but I don't see anything external to regulate the compressor pressure. There is just the electromagnetic clutch on or off.

Also, if you know what the working pressures should be, that would help. The Bentley manual can just come out and tell you in psi what the high and low sides should be. Thank you. mark
 

DanG144

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Chapin, South Carolina, USA
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2005 A4 Jetta 5spd
You can convert this to a fixed displacement compressor, fairly simply.

Google search:

Decreased Cooling In GM And VW
Cars And Trucks Could Mean A
Faulty Refrigerant Control Valve,​
Not A Failed Compressor
 

AndyBees

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Southeast Kentucky
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Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
Wow! Dan, that is an excellent link to a very informative write-up on the GM and VW AC Compressors with the Refrigerant Control Valve (RCV).

Also, thanks to Mark for bringing this circumstance to the board and starting a Thread on it!

So, Mark, as I understand the write-up, a Thermostat (as already installed in the VW Vanagon AC Systems) is all that's necessary once the RCV has been eliminated. The Thermostat (sensor) cuts-off AC compressor when the temp reaches the desired setting.

You know, the inside of the back on that VW Compressor (TDI model), looks just like the inside of the old '84 Vanagon model...........too bad the bolt holes, etc., are not the same!

EDIT: However, if there's no problem with the RCV, I assume it would be best to just leave it alone! Is that right?
 
Last edited:

jjordan11

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1988 Audi 80 quattro PD130, 1982 Westfalia TDI
Going from what I can remember from my past experience the low side sits between 28-32 psi and the high side is between 240-260 psi. It could get a little higher on a really hot day.
 

AndyBees

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Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
Mark, I just did some "measurements" and it appears the compressor from the '84 Vanagon will fit up to the TDI mounting bracket.

The bolt holes are approximately 0.003 smaller on the older compressor. The distance from mounting holes (both directions) is the same on center.

As I've stated previously, my '84 AC Compressor's line fittings are both the same size and are #12. The 508s are #8 and #10 on some models.

In my case, a Serpentine pulley set-up would be perfect. But, at this point, I believe cutting the fittings off/out of the old compressor and having them welded to the TDI compressor blocks is the best way to go!

And, it is sure good to know about the RCV valve!
 

DanG144

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2005 A4 Jetta 5spd
I am not sure why you would need to make the compressor a fixed displacement one for the system to work.

I did not understand why the type of expansion valve was signifigant.


Even in an old orifice tube sytem.
The compressor's mechanical RCV will try to maintain about 25 psig or so. If you put it in a system that was intended to cycle on low pressure at a point above that - the compressor will cycle off before it can load. But if the low suction pressure cutout is low enough, then the compressor can just start and run, feeding the orifice tube.
 

AndyBees

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Location
Southeast Kentucky
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Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
Dan, Mark was having cooling issues with his set-up. He is using the TDI Compressor with the old Vanagon system. Seems the pressures did stack up according to what they should. So, he was doing research and discovered this RCV thingy and was thinking that may be why his AC does get cold enough to hang meat.

Now, that's my assumption based on this Thread and comments in my conversion Thread.

Also, I'm attempting to do the same MOD with the AC system on my '84 Vanagon. I don't think the Vanagon system (at least the early models) had low or high side sensors. I cannot find one on mine!
 

markward

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Location
Loxahatchee, Florida
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82 Vanagon and 2011 JSW
I am back from the shop and here is what I found. For the record. My AC system is not a VW system. It is an aftermarket unit from Vintage Air for custom cars and hot rods. Their specs are 6 - 12 psi steady state at 1500 rpm on the suction side. High side should be 160 - 250 psi depending on ambient and condensor efficency. The vintage air expansion valve is designed to operate at the lower pressures which would have the effect of lowering the evaportator core temp. So better cooling. There is a relationship between the low side pressure and the evaporator core temp. The system has a conventional ac thermostat with a pig tail into the evaporator core that shuts the compressor off before the evap ices up. The expansion valve also has a pig tail attached to the low side of the evap line externally to regulate the opening in the expansion valve.

I could not get below 25 psi even with recovering half of the freon out of the system. I contacted Vintage Air Tech support and we were going over the usual problems when I mentioned the Compressor was not a fixed displacement system. The tech advised their a/c systems will not work with variable displacement compressors. The TDI compressor seems to keep compensating for what it thinks the low side should be.

As luck would have it, we had no 7/16ths bolts in the shop. I decided to chuck the valve mentioned in the article into a lathe, cut it down removed the innards tapped the inner bore and installed a 1/4 20 set screw to plug it. To make it solid. It is machined with a shoulder to center the highside reed plate and the reed plate retainer. We also took the time to examine the compressor. There is another peice in the very center of the compressor that seems to be a part of the displacement valve that is not mentioned in the article. So, I put it all back together with my disabled valve. It was a bit difficult to tighten the center bolt because it holds the high side reed plate and the retainer. Nothing to keep it from spinning as you tighten it. After a couple tries, I did get it centered and tight. For now, I reused the gaskets.

I pulled a vacumn on the system for about an hour and charged the system with the recommended 2 pounds of r134. There is definitely an improvement in the pressures. I can now get down to 10 psi on the low side and was seeing 40 degress at the center vents. Not sure why, but the high side was creeping up to the point the the radiator fan went to the second speed, which means high side is above 260 psi. I let a little freon out to drop the high side and then noticed that when the radiator is on the second speed, it is back feeding power to the relay that turns the compressor on an off and the 1st speed fan. That bypasses the compressor thermostat. So, I may need to add a diode or an additional relay to isolate the two. Seemed like a good idea when I wired it. Did not take into consideration power back feeding.

Andy, I am still not exactly 100% sure if the TDI compressor is still compatible even with the valve disabled. Doing my reading, The Sanden 508 and the later Sanden SD-709 for r12 and the SD-7H15 for r134 all have the same external dimensions. Some have ears and some are bolt through. Nostalgic Air in Tampa lists a lot of different head plate options. I emailed them to ask if the had a compressor that might be adapted. That was late Friday. Supposedly the SD 7 series fixed rate compressors are an improvement over originial SD 508. I am going to sort out my electical problem tomorrow and also bypass the heater core to be sure that is not causing the higher than expected vent temps.

Andy, thank you for checking the compressor ear dimensions. We had a bad TDI compressor at the shop. I pulled it apart before working on mine. Sort of a trial run. So I have the mounting bushings to adapt to a replacement compressor and if you have a problem, a spare TDI rear compressor cover plate. If I can't get my pressures to Vintage Air specs, I may go ahead and adapt the SD-7H15 to my engine. Since you are using the Vanagon AC system, you may not run into the same pressure problem I am seeing. My back is killing me. Time to hit the showers. p.s. DanG, you were a tremendous amount of help and if we make it to TDI fest and you are there, I owe you a drink. mark
 

DanG144

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Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
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2005 A4 Jetta 5spd
I am back from the shop and here is what I found. For the record. My AC system is not a VW system. It is an aftermarket unit from Vintage Air for custom cars and hot rods. Their specs are 6 - 12 psi steady state at 1500 rpm on the suction side. High side should be 160 - 250 psi depending on ambient and condensor efficency. The vintage air expansion valve is designed to operate at the lower pressures which would have the effect of lowering the evaportator core temp. So better cooling. There is a relationship between the low side pressure and the evaporator core temp. The system has a conventional ac thermostat with a pig tail into the evaporator core that shuts the compressor off before the evap ices up. The expansion valve also has a pig tail attached to the low side of the evap line externally to regulate the opening in the expansion valve.

I could not get below 25 psi even with recovering half of the freon out of the system. I contacted Vintage Air Tech support and we were going over the usual problems when I mentioned the Compressor was not a fixed displacement system. The tech advised their a/c systems will not work with variable displacement compressors. The TDI compressor seems to keep compensating for what it thinks the low side should be.

As luck would have it, we had no 7/16ths bolts in the shop. I decided to chuck the valve mentioned in the article into a lathe, cut it down removed the innards tapped the inner bore and installed a 1/4 20 set screw to plug it. To make it solid. It is machined with a shoulder to center the highside reed plate and the reed plate retainer. We also took the time to examine the compressor. There is another peice in the very center of the compressor that seems to be a part of the displacement valve that is not mentioned in the article. So, I put it all back together with my disabled valve. It was a bit difficult to tighten the center bolt because it holds the high side reed plate and the retainer. Nothing to keep it from spinning as you tighten it. After a couple tries, I did get it centered and tight. For now, I reused the gaskets.

I pulled a vacumn on the system for about an hour and charged the system with the recommended 2 pounds of r134. There is definitely an improvement in the pressures. I can now get down to 10 psi on the low side and was seeing 40 degress at the center vents. Not sure why, but the high side was creeping up to the point the the radiator fan went to the second speed, which means high side is above 260 psi. I let a little freon out to drop the high side and then noticed that when the radiator is on the second speed, it is back feeding power to the relay that turns the compressor on an off and the 1st speed fan. That bypasses the compressor thermostat. So, I may need to add a diode or an additional relay to isolate the two. Seemed like a good idea when I wired it. Did not take into consideration power back feeding.

Andy, I am still not exactly 100% sure if the TDI compressor is still compatible even with the valve disabled. Doing my reading, The Sanden 508 and the later Sanden SD-709 for r12 and the SD-7H15 for r134 all have the same external dimensions. Some have ears and some are bolt through. Nostalgic Air in Tampa lists a lot of different head plate options. I emailed them to ask if the had a compressor that might be adapted. That was late Friday. Supposedly the SD 7 series fixed rate compressors are an improvement over originial SD 508. I am going to sort out my electical problem tomorrow and also bypass the heater core to be sure that is not causing the higher than expected vent temps.

Andy, thank you for checking the compressor ear dimensions. We had a bad TDI compressor at the shop. I pulled it apart before working on mine. Sort of a trial run. So I have the mounting bushings to adapt to a replacement compressor and if you have a problem, a spare TDI rear compressor cover plate. If I can't get my pressures to Vintage Air specs, I may go ahead and adapt the SD-7H15 to my engine. Since you are using the Vanagon AC system, you may not run into the same pressure problem I am seeing. My back is killing me. Time to hit the showers. p.s. DanG, you were a tremendous amount of help and if we make it to TDI fest and you are there, I owe you a drink. mark

Mark,
Good job on the workaround.

As you probably know, unless you have two much refrigerant in the system (and thus go to pure liquid on the compressor discharge) the pressure of the discharge corresponds directly to the temperature of the discharge.

You may simply have to get better cooling. Better fan, larger surface area on the condenser. You can pretty much tell what is going on by spraying water on the condenser. This drops temperature, and thus pressure, unless you are 100% liquid. The pressure/temperature relationship is at the hottest point of the system.

Mark,
I have an annual trip to Colorado with all my brothers and my son. It is always the time period for the Fest. So I never get to go.

There will undoubtedly be some tidbit of info that you provide that helps me sometime.

Good luck. Great project.

Dan
 

AndyBees

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Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
Mark, thanks for all your research. Yes, I knew your system is from Vintage Air....I was running in and out today checking an eBay item and wasn't thinking straight when I made that comment!

Well, the Mud Bogg event went off pretty good. All funds taken in is for Shop with A COP come Christmas for the kids!

Now, my welder will get back to those welding jobs I have lined up for him.....motor mounts, heater pipe, exhaust system, etc.

Well, I really like a nice AC system. So, hopefully I will be able to keep the old system and adapt it to the TDI compressor! I'm going to do a junk yard run Tuesday to see if I can come up with some parts that will be of use in doing Mods on the AC connections!

Thanks Mark and Dan!
 

AndyBees

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Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
Here are some photos of the SD7V16 ('02 TDI) AC Compressor and the Sanden (one of the 508 models) from the '84 Vanagon. I'm not sure what the model number is of the Vanagon compressor due to a defaced sticker. It does have U508 S58 on the body!

The measurements indicate that only some minor reaming/boring out of the bolt holes will allow mounting the earlier model Sandens on the TDI engine bracket. Of course, the pulley and clutch assembly would need to be for a Serpentine Belt!

This is the TDI compressor showing the distance between the front and rear mounting holes (about 3.230 inches)


This is a similar view of the AC Compressor from the '84 Vanagon. The measurement is roughly the same


This is a view of the TDI compressor showing the center-to-center distance of the bolt holes from one side to the other. It looks to be about 4.15 inches.


This is a similar view of the Vanagon compressor. If you look closely, you can see the measurement is about the same as the TDI compressor.
 

markward

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Location
Loxahatchee, Florida
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82 Vanagon and 2011 JSW
Andy, thank you for taking the time to make the measurements. Here is a link to the updated SD508 compressor called a SD- 7H15. It has a serpentine belt option, but is still a fixed rate compressor. There are a lot of options for mounting, hose fittings, and pulley arrangements. http://www.acpartsguys.com/rv__motorhome_compressors

Here is a link to Nostalgic Air. I have not dealt with them other than calling once to find out about their aftermarket air system. I was not impressed by there willingness to help in my project. Here is a list of some of the compressor covers they sell. You might be able to come up with one to fit your #12 lines. Are both the high and low sides #12? http://www.nostalgicairparts.com/ac/sanden-compressor-backs-heads-19.php

I corrected the electrical backfeeding by adding a second relay for the low speed radiator fan. Now when the rad fan is kicked up to the second speed by High Side Pressure or Engine Temp, 12 volts is not back fed to the AC compressor circuit. Road test to and from town seeing 40 degrees out the center vents. This is a sizable improvement in cooling vs the unmolested TDI compressor.

In my heart of hearts, I think the best solution would be to install a proper compressor suited to the AC system. I can understand what I have done by disabling the internal valve, but don't think that is the best fix. I will let it rock for now, but maybe if it fails, go to a more conventional compressor.

mark
 

markward

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Dan, the amount of oil was a little confusing. Vintage Air says their systems do not require the addition of any oil during the installation. Their new compressors also come filled with oil. I missed that instruction originally and blew about 8 oz's into the system on top of what I filled into the compressor originally. The compressor came with the engine and had been sitting in the shop for years and was empty.

For this repair, I made a dipstick for checking the oil level with the compressor installed, since I did not remove it this time. The manual called for around 6 ounces of compressor oil. I added about 5 ozs. There is not really a passage between the reed plate and the compressor case that would allow the oil in the compressor to run out. I think that evacuating it may have removed the original oil. Because when I pulled the rear plate only a few drops of oil came out.

We use a compatible oil for R134 systems. It has the uv die mixed in as well. I don't think it is PAG or Esther. It comes from the parts house and is supposed to be compatible with all 134 systems. The system has been charged and evacuated twice now, so the oil should be ok. mark
 

AndyBees

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Joined
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Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
Yes, Mark, both of the connections on the '84 Vanagon AC Compressor are #12. I feel really dumb not noticing that they were the same size and also not the normal #10 and #8 as on most SD 508 models!
 

AndyBees

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Southeast Kentucky
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Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
Dead link

Dan, I check my cross post reply. I found the link in your earlier thread. I had skipped over it, thinking it covered GM. If anyone else comes across this thread. From Dan. http://www.aircondition.com/tech/get...9WYWx2ZXMucGRm I will report how it works. Going to give it a shot tomorrow. mark

Since the above link no longer works, try this one: www.aircondition.com

Once there, do a search on Internal Control Valve (takes a few seconds to load)......then scroll down until you see the article/link on Decreased cooling in GM and VW cars and trucks...... The write-up about the valve is in Adobe. The ICV must be eliminated in order to work properly on an old VW vintage system.

Also, read Dan and Mark's comments in this Thread!
 
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