Procedure for rebuilding AC system...how much refrigerant, oil, torque specs?

Drewser

Veteran Member
Joined
Jul 19, 2002
Location
Mesa, AZ USA
TDI
'04 Jetta TDI Wagon, '04 Passat TDI, several in past
I really miss having a Bentley for the Passat. Not sure what gives with that...it was my bible with my Jetta's. Most of what I've done so far has pretty decent write-ups. Other than compressor and condenser removal, haven't found any for this. I do have a Bentley for my 04 Jetta...not sure how similar the AC system is.

So need some help here. Ordered parts to fix the AC system and here's my plan. Anything I should check before digging in? I heard the relay can go bad...do I just check for 12v at the compressor to know it's ok?

1. System has already been evacuated, refrigerant recovered (you're welcome, environment).
2. Going to hook vacuum pump up to system and see if it holds vacuum.
3. If yes, going to remove compressor, orifice tube (where is this?), dryer, and condenser.
4. Flush evaporator core with AC flush. Hoses too.
5. Fill new parts with oil (how much oil in each part? Total? Drain oil from compressor first?) Put stuff back together, install new parts including o-rings. (anyone have torque specs?)
6. Pull vacuum on system and check for leaks.
7. Recharge system with R134a. Was going to use a kitchen scale and go by weight, but how much does system take? Will have gauges attached...do I go to a certain pressure?

It's been years since I've messed with AC, and then I had a friend showing me what to do. I'm borrowing the gauges and vacuum pump from a friend and doing O'Reilly tool rental/borrow on the flush gun. I'm just sick of paying so much money to have the car worked on. $2600 for the mechanic to do this is crazy talk, at least for an '04 with 238k miles on it.
 
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zzdiesel

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Dec 10, 2010
Location
sask. mostly now Wa.
TDI
05 passat tdi Geared BSM and Bewcam 2nd 2005 deleted ,converted and bew cam stage 2 Malone3 tune.
Where was the original leak?
High side is the smaller diameter pipe.
Orifice tube is in the high side tube at the last connection before the connection to the evaporator, up near the battery.
R134, there should be a sticker on the inside of the hood, Mine says 600 grams.
Not sure on the oil, but the new compressor may come with the required amount.
If the mechanic was also changing the evaporator then the price may not have been too much out of line.
 

Drewser

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Jul 19, 2002
Location
Mesa, AZ USA
TDI
'04 Jetta TDI Wagon, '04 Passat TDI, several in past
Their plan was to just flush the evaporator. But for that much I'll do it myself. Hope the sticker is still there and readable. Thanks for the info.
 

Drewser

Veteran Member
Joined
Jul 19, 2002
Location
Mesa, AZ USA
TDI
'04 Jetta TDI Wagon, '04 Passat TDI, several in past
Oh, and original leak was one of the hoses going to or from compressor. But after replacing and recharging, they couldn't get the clutch to engage. Going to test at connection by power steering reservoir, see what's going on. Maybe relay? Or compressor is seized. Sat for about 3 months before I got back to working on it.
 

TurboABA

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Jul 24, 2010
Location
Kitchener, ON
TDI
2010 Jetta 6spd MT, 2014 Touareg Execline
I'd suggest doing some more troubleshooting before "rebuilding the system", but that's my approach.
Depending what what brands you're working with etc, you should be able to find lots of info on the respective manufacturer's sites....
Here's some I have laying around to give you an idea and get you started in the event that it applies to your setup.

For "missing" manuals, there's always https://erwin.vw.com/erwin/showHome.do
Some of my AC stuff that's laying around:
 

Drewser

Veteran Member
Joined
Jul 19, 2002
Location
Mesa, AZ USA
TDI
'04 Jetta TDI Wagon, '04 Passat TDI, several in past
How different is the B5.5 AC system from the MKIV system? I assume capacity would be different, but troubleshooting and testing procedures? Would the MKIV Bentley help here?
 

TurboABA

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Location
Kitchener, ON
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2010 Jetta 6spd MT, 2014 Touareg Execline
Let's start at the beginning.
What do you know other than "the ac doesn't work"?
Is the system charged and holding a charge? There are pressure sensors which will not allow the compressor to engage if pressure is low.
Is your relay good? Fuses?
Have you checked for power at the compressor? (or loose connections, etc)
Have you visually checked that the compressor clutch isn't engaging or are you only suspecting it?
Did you scan with VCDS for any clues? Looked at any measuring blocks or done any output tests?
 

Drewser

Veteran Member
Joined
Jul 19, 2002
Location
Mesa, AZ USA
TDI
'04 Jetta TDI Wagon, '04 Passat TDI, several in past
So here's the situation. Bought the car in May, AC wasn't cold so had mechanic charge the system. AC cold. Then parked the car in June as it needed timing belt and BSM delete and was 120 degrees outside. Pulled it out of storage a week and a half ago to do timing belt and BSM delete. Had lock carrier off, but did not crack AC system (put condenser to the side). Put everything back together and AC wasn't cold, so figured it leaked out during storage.

Since I had just spent 3 days tearing into the car and had it all back together, I took it to my mechanic. He found a leak in one of the hoses going to or from the compressor. Replaced the $250 hose (plus $250 in labor, including recharge) but then couldn't get the compressor to engage.

Now from here out, I'm going off what mechanic told me. System held vacuum, no additional leaks detected. They tested for 12v at the compressor and saw power but couldn't get it to engage. Revved engine, nothing. Told me compressor was bad, that they recommended a whole new system for $2600. I said I wasn't interested and asked them to evacuate the refrigerant so I could replace stuff myself. An issue (another thread) has the car still at mechanic.

So I'm getting the car back Thursday or Friday and will be working on it this weekend. Have a whole system coming tomorrow from RockAuto (compressor, condenser, dryer, orifice, and oil) and am borrowing a friend's vacuum pump and gauges. However, I'm considering first charging the system and checking things. Some of the questions I have are as follows:

1. The green connector by the power steering reservoir...that should have 12v when the AC button is on, right? And if I supply 12v to the compressor side of green connector, it should engage clutch, right?
2. Is there a way to test the pressure switch?
3. Is there a way to test the under dash relay?
4. How much refrigerant does an 04 Passat take? (will look for label when I get car back)
5. How much oil does system take? Or is this based solely on compressor specs, and you divide it among the system (bentley has chart for A4), unless compressor already has oil...but since it's coming with a bottle of oil, I'm guessing it won't.
 
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oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis (where it's safe)
TDI
There are just too many to list....
The B5's A/C system is 100% different that the A4. B5 uses an orifice tube non-cycling system, A4 uses an expansion valve variable compressor.

The B5s (most of them) use a Denso compressor. A few had Zexel, but I am pretty sure every AWM and BHW uses a Denso.

The B5's HVAC has no fan control module, there is no solid state control of anything like the A4. They use the older setup... relays and series resistor. The clutch relay, often called the retardation relay, is in the inside panel, you can get at it by reaching in through the fuse box door. These often fail, and cause no clutch engagement.

The electric cooling fan (there is only one) should come on low speed with the engine running and the A/C switched on, regardless of charge level or clutch engagement. High speed fan is commanded when refrigerant pressure goes beyond a certain threshold. They just use a relay (in the underhood/cowl box, next to the ECU) to bypass the resistor, which is mounted down low on the left (driver) side unibody rail, on the underside, near the intercooler. The fan connector is near the other connectors, in the holder for all the wiring to the lock carrier assembly, under the PS fluid reservoir cover. The connector with the two big wires, brown (always ground) and the red one (power, depending on fan command). The compressor wire also runs across the lock carrier, and is the little green single wire connector in that same group as the fan. It goes down, across, then has another connector before the compressor, on the right charge air tube crossover pipe.

They hold 600 grams.

There is no OBD for the HVAC (unless you have Climatronic, which you do not... no BHW does, that was only on the W8s and the V6 GLX).

The orifice tube is in the line split near the cabin filter, the part where it goes from fat to skinny.

If you have to ask which is low and which is high, you probably should not be working on the A/C system. ;)
 

TurboABA

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Joined
Jul 24, 2010
Location
Kitchener, ON
TDI
2010 Jetta 6spd MT, 2014 Touareg Execline
No idea on any of your specifics as I don't have your service manuals to give you those. Either locate those "free" by spending time to search them, or pay a little at the above suggested source and download specific info to your exact setup... everything from wiring diagrams to maintenance manuals.

That being said, you should be able to look for and potentially test a few things just by assuming that the system has indeed been charged.
If you're going to have gauges on you, you can quickly check that it has pressures.

The following is more or less generic info that applying across a lot of configurations.

Let's assume that the system is charged and not leaking.
Start the car and get under it or to a point where you can see the compressor pulley (after checking that the drive belt is on).
Have someone turn the a/c on and visually check the compressor clutch is engaging (the center portion should start spinning with the pulley)

If that fails, check for "signal" at your clutch connection, or "green connector" as per your #1. It should be getting power when the a/c is activated.
You can also use a jumper to supply it with power bypassing the rest of the system to "validate" that your clutch engages.

If that fails, check the relay where said connector should be getting a signal for..... I want to say it's something like 384 above\behind your fusebox above the pedals......

Also check that you didn't disconnect the 4 wire pressure switch (I wanna say behind your passenger foglight).......

You can just jump the relay terminals to bypass it if you suspect it's fubar.
 

Drewser

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Joined
Jul 19, 2002
Location
Mesa, AZ USA
TDI
'04 Jetta TDI Wagon, '04 Passat TDI, several in past
Thanks...Turbo and OH, you've confirmed I'm on the right track. I know where the relay is and pressure sensor, as well as the "green connector" wire. I've been intimate with those during my latest forays into Passat-land. I should probably check all those connections thoroughly since I've had them all disconnected recently. Since the system has already been evacuated, now I have to make the decision to recharge the system and test, or just flush and put the new parts in and then recharge.

If anyone has tricks for testing components without recharging the system I'm all for it. Maybe short the green wire to see if the clutch at least engages? Will that hurt it on an empty system if only for a few seconds?
 

TurboABA

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Jul 24, 2010
Location
Kitchener, ON
TDI
2010 Jetta 6spd MT, 2014 Touareg Execline
I feel like he's already jumped the gun at this point by evacuating the system, so validating one simple thing won't tell him (us) much.
Since he already had a "weak working" a/c not that long ago, I'd be fairly confident in going out on a limb and saying that his clutch and compressor are fine.
 

Drewser

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Jul 19, 2002
Location
Mesa, AZ USA
TDI
'04 Jetta TDI Wagon, '04 Passat TDI, several in past
Just trying to decide if it's worth charging the system before changing components. Sounds like it might be.
 

Windex

Top Post Dawg
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Apr 1, 2006
Location
Cambridge
TDI
05 B5V 01E FRF
I've read through most of the above... So if I missed a detail, sue me.

You indicated that the shop wants to flush the condenser, why? Do they suapect a restriction? If so, what were the running pressures that made them think that?

Now that the refrigerant has been recovered, how much? Any refrigerant recovery machine should have a scale to weigh the amount taken out...

Also, as indicated above, you're asking questions which are AC 101 level, but you are ordering parts and asking diagnostic advise at a more advanced level... This is fine, it's your money, but that disconnect between levels is a recipe to waste money.
 

Drewser

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Joined
Jul 19, 2002
Location
Mesa, AZ USA
TDI
'04 Jetta TDI Wagon, '04 Passat TDI, several in past
I may have misspoken...they were going to replace all parts except evaporator and just flush the evaporator. I assume due to the work to get it out. And they did the recovery so I'm not sure how much went in or out. As others have said, I'll look for the label when I get the car back. I don't remember seeing it, but I never looked specifically for it either so it's probably there and will answer that question.

As to the AC 101 questions, I'm not sure why I asked which was high side and which was low...that was really a dumb question. I'm going to delete that now out of embarrassment. I know the procedure, how to use gauges, vacuum pump, etc...Just been about 6-7 years. Was really just looking for specific info related to the B5.5 Passat. This is my 5th TDI but first BHW, and first VW I've messed with AC on. Have done basic work on a Jeep and Civic in the past.
 
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Drewser

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Joined
Jul 19, 2002
Location
Mesa, AZ USA
TDI
'04 Jetta TDI Wagon, '04 Passat TDI, several in past
Got car back, jumped the AC wire and could hear clutch engage. So vacuumed system for an hour, then went to draw refrigerant in. Only about 50 grams went in. Car was running, AC on, so I jumped the compressor wire again. I can see the clutch spinning when I do that but it does not draw any more refrigerant in.

Is it safe to say compressor is bad?
 

Drewser

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Jul 19, 2002
Location
Mesa, AZ USA
TDI
'04 Jetta TDI Wagon, '04 Passat TDI, several in past
Yes, adding to low side using ac gauge manifold and cans with the top that screws on, punctures the can and connects to the manifold with yellow hose. However, I'm thinking the blue coupler may not be pushing the valve down in the low side. Going to get a different set and see if that makes a difference.
 

Drewser

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Jul 19, 2002
Location
Mesa, AZ USA
TDI
'04 Jetta TDI Wagon, '04 Passat TDI, several in past
Ok, it's a bad coupler. I pulled vacuum then shut coupler valves and manifold valves. Gauges showed vacuum. Then I opened manifold valves to release vacuum from the lines. Reclosed and opened high coupler, high gauge went back to vacuum. Opened low, no change in gauge. Grabbed a new gauge set from AutoZone and all worked as expected.
 

Drewser

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Joined
Jul 19, 2002
Location
Mesa, AZ USA
TDI
'04 Jetta TDI Wagon, '04 Passat TDI, several in past
That was the problem. Got the system charged and air got cold. However, compressor was making a funny sound so since I already had all the parts from RockAuto, I rebuilt the system. Recharged and have ice cold AC now for way less than mechanic wanted. Wasn't too bad a process either...actually enjoyed it.
 
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