Stumped on A/C issues

Trip7

New member
Joined
Jul 16, 2018
Location
Riverside
TDI
2001 golf tdi
Had an issue this year with the A/C on my 01 TDI. There’s no cold air anymore. The climate control switches all work properly. The blend door has been checked and fixed for lost foam. Radiator fans both work. Compressor clutch engages. But still no cold air. Took it to a shop and their diagnosis was that there was no leaks, just needed a recharge. They did that and it still doesn’t blow cold.
Does anybody have any advice where to check from here?
 

ToxicDoc

Veteran Member
Joined
Mar 1, 2018
Location
Virginia, US
TDI
2001 Jetta, S7, .216
What are the system pressures? If every is truly working (clutch engaging, etc) then it could easily be the pressure valve (inside the compressor). I'm guessing the shop you used doesn't do VW/Audi often.
 

Matt-98AHU

Loose Nut Behind the Wheel Vendor
Joined
Apr 23, 2006
Location
Gresham, OR
TDI
2001 Golf TDI, 2005 Passat wagon, 2004 Touareg V10.
In their diagnosis, did they bother taking note of what the pressures did (if anything) when the compressor clutch was switched on and confirmed engaged?

It's not unusual for these old Sanden SD7V16s to have the internal, mechanical refrigerant control valve stick, causing the swash plate to not change angles to make for effective displacement of the refrigerant. Can't move refrigerant well, it doesn't make much if any pressure differential. Having the pressure differential is what makes it cold.

When the compressor is off, the pressures on the high and low side equalize. When the compressor is on and working correctly, the low side should dip to 25-30 PSI and consistently stay there no matter the ambient temperature. The high side can vary greatly to somewhere a little over 100 PSI to 250 PSI depending on ambient temperature.

But if, say, you have 90 PSI (give or take a fair amount depending on ambient temperature and charge level) on both sides and when you switch the compressor on, the pressures don't change or change very minimally... most likely is a bad RCV inside the compressor. Most shops are only going to want to replace the whole compressor since the vast majority of the wholesalers out there don't have internal compressor components.
 

Bengoshi2000

Veteran Member
Joined
Jun 24, 2013
Location
Triad NC, USA
TDI
2002 Golf (0M1)
It's not unusual for these old Sanden SD7V16s to have the internal, mechanical refrigerant control valve stick, causing the swash plate to not change angles to make for effective displacement of the refrigerant. Can't move refrigerant well, it doesn't make much if any pressure differential. Having the pressure

That same control valve failed in my compressor. There's a thread flying around on here somewhere on how to replace it. Seems the part was like $70 shipped. Installing it was tedious but well within the skill set of the average wrencher.
 

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
It's not hard to change the RCV if that's what has failed.

However, frequently the reason it failed is that it got filled up full of gunk that was created in the compressor over time due to overheating (which, in turn, is frequently caused by the fans not working properly.) Once this cycle starts its very destructive because the lack of compression means less refrigerant and oil is circulating and it is that circulation that removes heat from the compressor itself.

A/C shops generally will not do just a swap of a single thing (like the RCV) because they don't want the callbacks on warranty work, so they'll insist on swapping the compressor and a complete flush or replacement of everything -- often including evaporator and condenser. The labor for that (removing the entire dash to get to the evaporator, for example) makes this one darned expensive job at the shop.

If you're up for it go ahead and try the RCV swap, just be aware that there are very good odds that you'll do it and within a very short period of time now that the refrigerant is moving again all the stuff that wasn't moving (including the gunk in the compressor) will now wind up everywhere and the system will shortly fail again. If, when you pull the end plate off the compressor, you find anything that looks black (e.g. carbon) or (much worse!) metallic in the old RCV or the cavity it goes into you may as well stop right there and just do the whole job.
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
TDI
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.
If all the electrical stuff checks out, get a set of gauges. It will be the tool you need to diagnose your issues. Shops are garbage.
 
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