Air condition too cold to the point of no air flow

[alex_tdi]

Hi Everyone,

I recently got my A/C compressor replaced because I guess it's just worn out after 136K miles.

After I got the car back, the A/C became super cold. It's like meat locker cold. I was ecstatic.

However, on a long drive I noticed that after around 30 minutes with the A/C on, the air coming out of the vent was as cold as ever, but the strength of the air flow was reduced dramatically. I tried changing the fan speeds and played around with the recirculation on/off. I could hear the fan speed increasing and decreasing, and also the change when I turn recirculation on/off. The airflow was weak even though the temperature was still super cold.

When I finally turned off the A/C, as the air temperature slowly increased, the air flow increased as well. After about 1 - 2 minutes, the airflow returned to normal. I have to keep manually toggle the A/C on/off to prevent the vent from "freezing up".

This is obviously a problem, but I'm not sure what could have caused this. Isn't there a sensor that toggles the A/C compressor on/off based on the temperature? Or do you guys think there's some moisture in the system that's freezing up the vents?

Thanks.

Alex

p.s. I have a 2001 Golf GLS with 136K miles.

 

[speed185187]

they over-charged your a/c system with too much freon.

 

[DanG144]

I do not think overcharging with refrigerant will cause this.
The classic cause is an undercharged system. The boiling downstream of the TXV is located at a small point, instead of in general in the evaporator. That point ices up, then the location of evaporation moves downstream a bit and this cycle keeps up until the whole evaporator is iced up.
Other potential causes are:
TXV malfunction. Many people are tempted by the very low prices of cheaply sourced TXVs. I would use a good one from VW or other known good source. Do you know if they replaced the TXV?
low air flow on the evaporator coil. (Dirty, clogged, plastic bag sucked into the fan)
Malfunction of the RCV (refrigerant control valve) inside your new compressor.

Most pros will replace the filter drier, TXV and compressor when they replace the compressor.

 

[alex_tdi]

When I first had problems with the A/C, the expansion valve was replaced. That didn't really fix the problem, so I had the compressor replaced. The mechanic told me that the dryer has to be replaced at the same time, so I assume he did that as well.

I'm hoping it's just a case of the coolant being too low.

Another thing thing happened today. I noticed that while I'm stopped at a stop light with the A/C turned on, I sometimes hear a very loud noise that sounds like something vibrating/rubbing. It's not a high pitched squeal like a belt that's slipping, but it definitely sounds like something was stuck for a brief moment but then returned to normal after a second or so.

Any guesses?

 

[SoTxBill]

When I first had problems with the A/C, the expansion valve was replaced. That didn't really fix the problem, so I had the compressor replaced. The mechanic told me that the dryer has to be replaced at the same time, so I assume he did that as well.

I'm hoping it's just a case of the coolant being too low.

Another thing thing happened today. I noticed that while I'm stopped at a stop light with the A/C turned on, I sometimes hear a very loud noise that sounds like something vibrating/rubbing. It's not a high pitched squeal like a belt that's slipping, but it definitely sounds like something was stuck for a brief moment but then returned to normal after a second or so.

Any guesses?

compressor is cycling off and on due to low pressure..ie too low on freon..

 

[chewyboy]

after reading this i'm a bit confused, why would any amount of AC work have an affect on the blower motor? it sounds like the airflow is what is wrong here at least with the air flow portion of it.

however the blower motor does not negate the possibility of them doing something strange to your ac system.

 

[DanG144]

Usually our systems will not cycle off and on on low pressure. If there is enough compressor discharge (high side) pressure to allow the compressor to ever kick on, then the pressure is always high enough from then on; the compressor will not lower the discharge pressure. There is no suction pressure switch or sensor at all.

Sometimes the compressor will cycle off on high pressure, or what the High pressure sensor reads as high pressure, if the fans are not running or the condenser coil is fouled - something that produces high temperatures and thus high pressures in the discharge side.

Look at the pdf entitled "May 99 to end of A4 manual air conditioner" in post #1 of this thread Mk IV AC and Fan troubleshooting for the approximate actuation pressures/temperatures.

 

[josh8loop]

after reading this i'm a bit confused, why would any amount of AC work have an affect on the blower motor? it sounds like the airflow is what is wrong here at least with the air flow portion of it.

however the blower motor does not negate the possibility of them doing something strange to your ac system.

Good question....The answer is that if the evaporator(directly in the air flow) freezes over it doesn't allow air to pass through. The evaporator shouldn't ever freeze over, and the issue must be addressed.

 

[oilhammer]

Wow, reading this thread.... some people really should not post at all until they go read a book on how A/C systems work... sheesh .

The problem is your evaporator core is freezing up, meaning it is actually getting TOO cold, and is dipping BELOW freezing. When this happens, the condensate, that normally will collect on the evaporator coils and drip off and out the drain under the car is actually freezing solid into ice. Over time, this ice blocks off the air flow through the coils, which (no pun intended) creates a snowball effect because it allows the evaporator to get even colder.

Normally, the expansion valve and compressor work in concert to get the pressure drop "just enough" to cause around 35 F or so evaporator coil temps.... meaning, "just above" freezing, so there is no chance the water can actually turn into ice, yet will allow the maximum cooling for heat exchange across the coils.

The expansion valve has a built-in thermo-bulb that is calibrated to keep this pressure from getting out of whack. What probably happened is the "shop" that installed the expansion valve used one from our Communist friends in China, which I assure you is in no way properly calibrated to match the original part on the car (they never are). And you got one that is so far out of whack it is allowing the evaporator core temp to drop below freezing. They may have even put a Chinaloy compressor on, and even worse, one of those rice and bamboo crumb filled things they call a "drier".

Do yourself a favor: your Volkswagen was equipped from the factory with a Sanden compressor, a Parker drier, and usually either a Valeo or Hella expansion valve. If any one of those pieces is NOT the above mentioned brands, replace it with one that is. Your local dealer of course can get all the correct stuff, but many aftermarket places can also get the proper stuff. Then, once Volkswagen parts are installed, your Volkswagen's A/C system will once again function they way it is supposed to.

 

[compu_85]

One easy thing to check: Look at the expansion valve on the firewall. It should have a black plastic heat shield over it. If it doesn't engine heat can affect its performance.

Shouldn't the evap temp switch cut out the compressor if the evap starts freezing?

-J

 

[16vjohn]

...Communist friends in China... Chinaloy compressor on, and even worse, one of those rice and bamboo crumb filled things they call a "drier".

Are you for real, dude? Could you be any more insensitive or racist? HOLY CRAP!!!

To Alex_TDI, even though oilhammer's comments were completely off color, he may be right about the quality of the parts. I think the best thing to do at this point is take it back to the shop that made the repair and ask them to fix it... I would think that an expensive repair and system overhaul like this would come with some kind of expectation that it should work properly. As much as I would like to tell you to go back and put OEM parts in, it's not realistic to ask you to throw $1,000 down the drain and do it all over again. Take it back to the shop and let them figure it out. In the future, learn from this experience and buy OEM parts.

 

[chromeBuddha]

Along with what the insensitive (tut, tut) oilhammer and others have said, the shop that did the work should have a record of how many ounces of 134a they put in the system after they pulled a vacuum. That doesn't grow on trees and any shop should have noted that in the repair notes. It will be a shame if they put some POS compressor in and tossed your Sanden on the scrap heap if it was a $23 control valve that could have saved the compressor...

If they replaced it with a non-variable displacement compressor, or the other mentioned crappy parts... They will not likely be able to stand behind their work, though I agree that they should. They likely charged you $400+ for an inferior compressor, drier and TXV and gouged you on the labor telling you that the whole front end has to come off (it does, to some extent, but it isn't really very time consuming). I am guessing you were in to them for some $700+ and now will have to jury rig a solution, such as adjusting the temp control knob to add enough heat to the equation to leave the blower on continuously (the reverse of what you may in the colder months using a max heat setting while engaging the A/C to help defrost/dehumidify the cabin air). Boy, did I not get enough sleep last night to put a coherent sentence together.

I definitely understand oilhammer's frustration with the trade policies of China and the disolving of our country's manufacturing base. But the same tarrifs I would support to try to move manufacturing back to the US are the ones keeping the VW diesel pickups out of the US market... And I would really like a torquey little truck that gets 30+ mpg...

Good luck with the resolution...

Check this link for what could have happened to initially degrade your system performance:
http://forums.tdiclub.com/showthread.php?t=283967

 

[oilhammer]

I have nothing against the Chinese, they make great food. But if you spent a week in my shoes, you'd learn to hate the poor quality parts they dump on our shores, too. I do not see how this is "racist". China is a COUNTRY, not a race. Get over it. And yes, they are Communists, which is what many of us do not understand... in the '60s if any store owner in the USA tried to sell anything with "MADE IN USSR" on it they probably would have been arrested. Yet today, our economy seems to run on this very same premise. Wally-world, anyone?

And yes, I am for real... cut open some of those Chinese driers and see what is inside. It seriously looks like ground up oatmeal and cardboard inside a little teabag. Not at all like the original desicant, which is a gray uniform material inside of a nice, formed tube-sock shaped thing with a sturdy frame so it won't spontaneously blow apart and send brown mystery chunks straight into your expansion valve. No, I am not kidding.

Cut open a Prothe fuel filter and see what mess is in there...

 

[visionlogic]

Are you for real, dude? Could you be any more insensitive or racist? HOLY CRAP!!!

And yes, I am for real... cut open some of those Chinese driers and see what is inside. It seriously looks like ground up oatmeal and cardboard inside a little teabag... Cut open a Prothe fuel filter and see what mess is in there...

Sensitivity to those troublesome little things called FACTS doesn't count anymore - it's not the way the game is played. One should only conduct oneself such that whatever the PC offense-de-jour happens to be is not committed.

 

[Keith_J]

This AC system is a beast, 7kW compressor with a maximum CoP of 2.2 means it is a 4 ton unit. That is enough refrigeration to cool a 2400 square foot house in the SW USA. It needs the variable displacement compressor, the proper receiver-dryer and the electronic controls/sensors to operate properly.

Replace the compressor with a fixed displacement compressor in the 150 cc/rev range and it will ice the evaporator. Plus the pressure limit switch will cycle the compressor, causing idle issues. IIRC, the stock specification Sanden compressor has a variation of 10:1 with a max displacement of ~160 cc.

I don't see any issues with knocking inferior Chinese goods. After WWII, Japan adopted the Deming Model, turning their industries into wold class operations. That Sanden compressor? Japanese design at the least.

 

[DanG144]

One easy thing to check: Look at the expansion valve on the firewall. It should have a black plastic heat shield over it. If it doesn't engine heat can affect its performance.

Shouldn't the evap temp switch cut out the compressor if the evap starts freezing?

-J

Unlike the fancier new systems or the older systems, the manual system in the MK IV has no evaporator temperature switch or sensor.

 

[16vjohn]

Weather the Chinese make bad parts or not isn't the point... The point is you should be able to convey an opinion and conduct yourself in a respectful manner when talking about other kinds of people and cultures. I thought we were over that kind of nonsense in this forum, I can see that I am terribly wrong.

The original poster didn't ask to be grilled over his choice for repair venue or parts used (by the way, we don't really know Chinese parts were used and this wouldn't be the first time a shop repaired AC incorrectly). We should be willing to help that person regardless of the circumstances without telling them to throw away a thousand dollars and do the job over again. That's bad advice and just makes you look like an idiot. Are you here purely for your own entertainment or do you actually care about helping a fellow diesel enthusiast? It might be easy for you to sit behind a blanket of anonymity here and act like a total child, but that doesn't mean I have to like it or agree with you.

 

[chromeBuddha]

How is the whether over there??? Sonny?

Honestly...this is an automotive forum. A mechanic expressing his frustration with crappy parts should hardly be the trigger for social or political debate. China is a communist country. Fact. oilH has seen a dryer made in China that had contents that look like rice and bamboo. Bummer. What else was there that could possibly give offense. There was no generic statement about people, just parts.

 

[oilhammer]

... I can see that I am terribly wrong.

....

Yep, we can agree on something. And yes, my frustration is about crappy parts, not people (other than people who choose to use said crappy parts). Not sure how this got turned into some political/race thing. Again, China is a COUNTRY, not a RACE. Unless you are like Hank Hill, and think ALL Asians must come from either China or Japan, in which case I have some Korean and Vietnamese friends who would really like to show you what being insensitive and racist really means. Oh, not all Latinos come from Mexico, too. Did you know that, or should you start calling all the folks here that ***** about Mexican-made Volkswagens racists, too? Sheesh, get a life!

 

[16vjohn]

Yep, we can agree on something. And yes, my frustration is about crappy parts, not people (other than people who choose to use said crappy parts). Not sure how this got turned into some political/race thing. Again, China is a COUNTRY, not a RACE. Unless you are like Hank Hill, and think ALL Asians must come from either China or Japan, in which case I have some Korean and Vietnamese friends who would really like to show you what being insensitive and racist really means. Oh, not all Latinos come from Mexico, too. Did you know that, or should you start calling all the folks here that ***** about Mexican-made Volkswagens racists, too? Sheesh, get a life!

Huh? Can you remind me where I said anything about all Asians being from China or Japan? ... or Mexicans, Latinos, Vietnamese or Koreans? I'm really trying to figure out what kind of point you're trying to make here besides proving to me how useless you really are. Who is it that needs to get a life here? You've added nothing to this thread but offend me and tell the OP that the parts he just bought should be immediately removed and replaced with OEM without knowing one single fact about them other than the evap is freezing over... Just exactly how much are you trying to take away from this thread? I'm trying to help and you are really just a parasitic drain. It's incredible how long they have allowed your incoherent ramblings to go on. Wow, just wow.

 

[dogdots]

I can't wait to see how this plays out ^^^

Oilhammer is a great person and has contributed more to this automotive community than about any other single person on this site.

If you are offended by his comments, too bad for you. How dare you try to be the PC police here. Last I checked 16VJohn, you are not a moderator here.

If anyone is offended by Oilhammers comments here, just overlook them and value the mechanical advise he provides. If you are offended by what you read from him, spend about 30 minutes in southern Mississippi and see how African Americans (sorry, was I just racist ?) are treated and what they are called on the street.

If you think his comments are racist you need a reality check. He is talking about inferior quality parts, not people. If you find Chinese made parts acceptable for your car, feel free to buy your parts from the lowest priced vendor you find on Ebay.

Grow up or go away.

 

[hevster1]

Are you for real, dude? Could you be any more insensitive or racist? HOLY CRAP!!!
To Alex_TDI, even though oilhammer's comments were completely off color, he may be right about the quality of the parts. I think the best thing to do at this point is take it back to the shop that made the repair and ask them to fix it... I would think that an expensive repair and system overhaul like this would come with some kind of expectation that it should work properly. As much as I would like to tell you to go back and put OEM parts in, it's not realistic to ask you to throw $1,000 down the drain and do it all over again. Take it back to the shop and let them figure it out. In the future, learn from this experience and buy OEM parts.

Brian is right.
His comments were on the nose 100%.
I for one am truly sick and tired of all the bleeding hearts complaining that someone is "insensitive" or whatever. The influx of cheap crap is costing jobs and is increasing the amount of garbage in our landfills tenfold. Junk is junk. Everyone makes it. Trouble is that 99% of the garbage comes from China and India. And if you are offended by someone's comment which clearly weren't directed at you, tough S***. Grow a thicker skin.
Brian is emphasizing quality which is clearly not made in China. If you do not see that or cannot comprehend what he is saying I cannot help you and I doubt if anyone else can.

 

[dogdots]

For clarification, IIRC the metering block on a MKIV is not a TXV ,which denotes a Thermal Expansion Valve, having a capillary tube filled with R134A that expands and contracts "Thermally" to counter act spring/diaphragm pressure and regulate a set temperature of boil off of refrigerant. A TXV requires the sensor (cap tube/bulb) to be in direct contact with the suction line leaving the evaporator, the MKIV's have a brass metering block, which is much more dependent on exact charge than a TXV system.

The charge must be measured exactly, since the only thing metering the flow of the refrigerant thru the expansion valve is the head pressure from the high side of the compressor, there is no bulb/diaphragm to control metering to a set temp.

By default, a metering block or orifice tube system, like in a domestic, will be less efficient and will be much more susceptible to improper charge causing lowered efficiency. The receiver/dryer in a TXV system also acts to store any overcharge liquid refrigerant (to a point of course) so the system can be slightly overcharged with no loss of efficiency. A simple restrictor system will have its efficiency more impacted by ambient temp, a hotter ambient will cause a rise in head pressure, resulting in more refrigerant flow thru a fixed orifice, thus a higher evap temp.

Undercharging a metering block system will result in too low of evap temp, and can cause freeze up, as explained by Oilhammer above.

 

[alex_tdi]

OK, so I went to the mechanic today and we confirmed that the air coming out of the vent was below freezing! (-1.2 degrees C). The plan was then to adjust the freon (R-134) in the system.

The first time he hooked up the car to the machine that he uses to charge / discharge the A/C, the pressure was reading around 40 psi on low and about 100 psi on high I think. He was going to recharge the system, but he said that he freon might have frozen up so we turned off the engine and let it sit for a bit. After about 10 minutes, he reconnected the machine to the car and there was no pressure reading at all.

After trying a few times he looked at the line valve (both the high and low) and he said that the rubber inside the valve was bulging out so they had to be replaced. A quick call to the dealer revealed they were $43 each! He said that the American and Japanese cars uses a metal pin style valve that he has plenty of, but he doesn't have any for VWs so he has to special order from the dealer.

So now I'm looking at spending another $100 bucks on two line valves that really don't get used much, so I don't understand how they could fail so easily.

Is this simply a case where the mechanic is not familiar with how VW parts look like? We don't have another VW to compare it against for reference.

Do you guys think I can use the other style valves? A/C has been around for so long, I find it hard to believe these parts aren't standardized yet. Or do you think they be fixed somehow?

Thanks.

Alex

Here are the parts in question (low side valve = 13, high side valve = 12):

 

[d2305]

4 ton sounds a bit too much. That's 48000 BTUs. As for the chicoms, we will be at each other's throats soon enough. http://en.wikipedia.org/wiki/DF_21D

 

[DanG144]

There has to be another VW in Los Angeles.
Those valves last pretty good.
I don't think I could tell by inspection if one was bad, unless it was spraying in my face.
I would doubt that they both failed at the same time.

I also do not think that you should be adjusting the freon level to try to adjust the evaporator temperature. This pressure/temperature is controlled by the RCV in the compressor varying the displacement of the compressor working with the TXV - either one can be at fault.

While you MIGHT get one operating point that worked ok, I do not think that it would work well for long, or if you changed operating conditions, (fan to low, fan to high, ambient temperature rise or fall.) I would not spend much money, time or effort trying to get to some magical refrigerant volume. A healthy system of this type works well from about 25 to 120% refrigerant charge.

Who supplied the compressor? Was the TXV and the filter-drier replaced?

 

[oilhammer]

Those fittings rarely need attention, seems something else is amiss. I will ask once again what the brand/origin of parts that guy installed on your car.

And 16vjohn, I just wiped more knowledge of Volkswagens off my butthole this morning than you will ever have, so please go fly a Chinese kite, will ya?

Better yet, complain to the mods.

 

[alex_tdi]

I'm going back to the mechanic and will ask for the replacement parts make.

One thing I'v noticed more and more is that when the compressor cycles on and off, there's a big vibration in the refrigerant lines and it's really loud and scary. I thought it was a belt vibrating at first, but I was able to see and feel the lines (cold) vibrating. One thing I did notice is that after I drive on the highway for a while (RPM >= 2000), the noise goes away.

Here is the movie I recorded today (http://www.youtube.com/watch?v=gMA5VVHh8xo). Do you guys think it's just because something wasn't anchored down? (i.e. a bolt is loose) or should I stop using the A/C cuz it signifies something serious like an impending engine failure.

 

[VW_Factor]

Weather the Chinese make bad parts or not isn't the point... The point is you should be able to convey an opinion and conduct yourself in a respectful manner when talking about other kinds of people and cultures.

Were they not talking about chinese parts? I didn't see anything about the Chinese as a people until people started talking about racism.

Regardless of who made the parts, if they are cheap and not working properly, people are going to speak of them (the parts, not the people) negatively.

 

[alex_tdi]

Everyone, please let's just drop the whole "Chinese" part and "Chinese" race back and forth posts. I am of Chinese ancestry and I have no problem using any part, made in any country, made by any people, as long as it performs up to spec. If the parts that were installed were inferior, let's just call it that and leave people/nation/race out of it.

Case in point: my Golf was designed in Germany, assembled in Brazil, and uses parts from all over the VW supply chain in Europe.

Has this car had its troubles? Yes. Do I sometimes think VW parts fail prematurely (window falling (cheap plastic retainer clip), fuel pump replacements, failed 01M transmission, LCA, drive axel, water pump, thermostat, etc.)? Yes.

Am I going to start blaming bad German design, bad Brazilian assembly, poor quality Spanish parts, etc.? No.

I have a problem with my A/C. Can we please just focus on the problem at hand?

Thanks.

Alex