Worn out A/C Compressor?

325_Guy

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Jun 21, 2011
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West Central Texas
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MkV Jetta
2006 BRM w/ 370k. Driven in West Texas so A/C use pretty much continuous from March-October. Recently I've noticed the A/C performing getting weak at idle, the air from the vents becomes noticably warm and humid. The fans are running and the car does not overheat.

I evacuated and recharged the system with the proper charge of R-134a and get system pressures both before and after recharge of about 55 low / 250 high at 100* ambient.

If I increase engine speed to 2000rpm or above, the A/C cools down to the way it used to be.

The compressor is on its 3rd RCV with last replacement in 2015 at about 175k.

I don't want to throw another RCV at it if that's not the problem, as the symptoms don't match (no delay in A/C cooling at startup, etc).

Is it possible the compressor is just worn out, given mileage and use?
 

Mongler98

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Mar 23, 2011
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98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
55 low 250 high seems fine.. you would ideally want 45 low with that temp and high side pressure but definatly not a indication of a bad compressor.
Dirty coil or not enough air movment is my guess here.
How often is the cabin air filter changed?
You may just have a dirty evap
How many micron did you vac it down to? New dryer filter? Nitrogen? Or did you just swag it for 30 minutes and just slap parts at it in the hot moisture air?
 

Rx7145

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Ohio
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2006 Jetta BRM
My current Theory is that the compressor gets weak over time and the condensers get damaged which affects efficiency. Of course the refrigerant control valves are prone to go bad as well which sounds like yours may be failing again.
 

325_Guy

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West Central Texas
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MkV Jetta
@Mongler98 - cabin filter changed every 40k since I bought it in 2011. Last time I had the system open in 2016 I vac'd it for 12 hours and got down to 250 or so micron. This time around I evac'ed, vacuumed for an hour down to 29mm, and recharged. Didn't open the system so didn't see a need for an extended process.

The air's pretty dry here, we see humidity in the teens most days ;)

@DivineChaos - didn't think of that, today I'll take a look and run some water through it.

So here's what got me on the compressor track also, I was measuring pressure, temps, and radiator fan activation with VCDS and even with doors open, A/C on max, I never got over 78% of fan activation. Idk how much a difference that would make or if that's even a concern since I don't have another Jetta to baseline this off of.
 

oilhammer

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outside St Louis, MO
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There are just too many to list....
You sure both the temp blend door and air recirc door are working correctly in the car? That may make the cooling not feel as good as it should, even of the system (compressor, etc.) is working fine.

Almost need to watch the duty cycle command of the RCV alongside another car to know *exactly* what to expect, they vary so much. FWIW, the original RCVs don't last forever, and the replacement Chinacool ones that most of us are using as replacements often last even less time, and in some cases are not consistent right out of the box.
 

325_Guy

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@oilhammer - I'm pretty sure, as the A/C will freeze you out of the car when I'm driving. It's only a problem when sitting still.

So here's another observation. I did some VCDS logging. At idle rpm and no change of conditions (doors open, a/c on high, no recirc), the reported system pressure varies from 215 to 265 psi. The commanded current is constant, 0.82A. Could that be the RCV? The RCV I have in there now has 200k on it.
 

oilhammer

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outside St Louis, MO
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There are just too many to list....
Every automotive A/C system is going to be more efficient while driving. The ram air effect is better, and the higher RPM of the engine means the displacement potential for the compressor is higher. However, the system should be able to keep the cabin comfortable at idle. Since these compressors do not cycle, you need to watch the refrigerant pressure value in the HVAC data to see if it is staying high enough, or getting TOO high.

If it is 90+ F degrees out, even at idle, the compressor should be capable of getting the pressure high enough to command the fans run on high speed (it may take a minute or two). I'd lean towards trying a new RCV at this point. They can tend to fail in a manner that makes the system only about 30% efficient, which is fine when driving down the road, but inadequate at idle speeds, especially in hot weather.
 

FlyingFin

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UK
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A4 Avant AFN
I had very similar symptoms on my A4 B5 1.9 Tdi Avant after it had done about 250k...

Eventually, I changed the internal heater blower and the issue disappeared...

I didn't feel any difference in the fan output, before or after, but it did sort the aircon issue out.


And at about £55.00 for a replacement from EuroCarparts, it was a cheap fix.
 

325_Guy

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West Central Texas
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MkV Jetta
This morning I hooked up VCDS and got the log going before I turned the A/C going and lo and behold! There is a delay as well. About 20 seconds between compressor current commanded and any buildup of pressure.

I'm going to replace the RCV and report back, is there a preferred or recommended source?

Edit: my 200k one is a Sunair EV-019, in case anyone is interested.
 

oilhammer

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outside St Louis, MO
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There are just too many to list....
20 seconds is a pretty long time. There is usually some change within 5 to 10, and it gradually ramps up.
 

borninabus

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Arizona
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-2013 JSW 6MT- -2006 Jetta DSG-
This morning I hooked up VCDS and got the log going before I turned the A/C going and lo and behold! There is a delay as well. About 20 seconds between compressor current commanded and any buildup of pressure.
can you elaborate a little on what measuring blocks you are montoring?
i am interested in collecting this info myself in regards to what i feel is a less than awesome a/c performance condition.
thanks!
 

325_Guy

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West Central Texas
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can you elaborate a little on what measuring blocks you are montoring?
i am interested in collecting this info myself in regards to what i feel is a less than awesome a/c performance condition.
thanks!
I use these blocks to get a decent idea of what's going on:
Engine Speed
Compressor - Current (specified)
Refrigerant - Pressure (bar)
Radiator Fan - Activation (actual)
Outlet Blower - Temperature (c)
Evaporator - Temperature (c)

You can find them easier if you open the module and go to Advanced Measuring Blocks, tick the boxes to enable them.
 

sptsailing

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2006 Jetta Manual, stock with Panzer Plate & Franko6 modified EGR cooler & CAM
Mine is on its 3rd RCV, and I found through experimentation that if I wait to turn the A/C on until the engine is at or above 2,000 RPM, it then seems to work fine thereafter, even at lower RPMs, such as idle. Frank06 had advised me to generally keep the engine near or above 2000 for best overall results. I am in Florida and also need the air almost all the time.
 

kbaisley

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Jul 31, 2002
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Midwest
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2006 Jetta TDI 5spd
Note for those with limited budgets ;-) The late model compressors from wrecked VW's are bolt in on most. I think they are the ones used in the 1.8 motor cars. I have used two of them on the BRMs I have in the current fleet. Both compressors were from late model wrecked cars with sub 15K on the clock. They're still working fine after a few years. I paid less than $50.00 for the compressor plus the freight.
 

325_Guy

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Location
West Central Texas
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MkV Jetta
So, the good news! The problem was the RCV. I replaced it, pulled and held 500 micron, and had the old, cold, awesome AC I was used to.
45psi low/ 320 high @ 100* ambient, evaporator temp 11*c.

The bad news! The snap ring let loose and explosively released the RCV and a full charge of R-134A.

Somehow, even though I verified the placement of the snapring with an inspection mirror and pressure tested the system to 200psi with nitrogen with no issue, it let go at full operating pressure.

Two questions:
1. Anybody have a snapring to measure? Mine is presumed lost and even if I find it I'm not reusing it.
2. Guestimation here, how much PAG 46 do y'all think I should add back in to replace what was blown out?
 

325_Guy

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West Central Texas
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MkV Jetta
For those that are following along, I've met with success.

To answer the oil replacement question, I found literature from Sanden (the compressor manufacturer) that indicated replacement of 44ccs of what they call SP-10 oil in the event of a "major system leak". SP-10 = PAG 46. Use pure oil, many you will find include either stop leak or "performance enhancers" and I wouldn't recommend those.

I've had a bit leak out during RCV replacements and manifold disconnects, etc, so I added 3 more ccs in addition to the 44cc called for and added 47ccs in total.

Here's a link (see page 27): Sanden Service Guide

Vacuum back down, 200 micron was my target and I got down to about 220, then added R-134a and voila! Evap temps of 51*F in 107*F ambient.

On the second round of installing the RCV, I used my snapring pliers and forced the snapring apart and this time I felt it expand out the 1mm or so it needed to to fully seat in its bore. I had never worried about that before when replacing the RCV but it bit my ass this time.

Anywho, hope this saga helps someone else out.
 
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