A/C issues checking off the list

09wingates

Well-known member
Joined
Apr 2, 2017
Location
Texas
TDI
2002 Beetle ALH Manual
so First off I do know my system has no charge in it at all. I have read elsewhere that without enough charge the system will not engage the compressor, fans etc. I have hot wired compressor which appears to kick and work fine. Unplugged the fan thermo switch on radiator and both fans work on either speed perfect with jump wire. A/c switch in dash lights up blower works etc. all fuses are good and wiring appears to be fine. So my question is this, until I can charge the system is there anything in else I can troubleshoot first? 02 Beetle ALH with 290k. Thanks fellas
 

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
Not really.

But if it has no charge then odds are there is moisture damage and the compressor is shot. The dryer definitely needs to be replaced any time the system is depressurized for more than a very short period of time (an hour or so).

Obviously the first thing is to find the leak; highest odds are the shaft seal on the compressor but it could be anywhere. If you don't have a refrigerant sniffer a can of refrigerant with UV dye and a black light will find it fast -- just don't use the stuff with sealants in it.
 

jrsride2002

Well-known member
Joined
Apr 18, 2013
Location
Houston, TX
TDI
'02 Jetta Wagon TDI
Yea man.
I might suggest going crazy about replacing ALL of the O-rings. If your dryer is shot, because of no pressure, it will be well worth the time and effort to replace them now.

I myself, am still chasing down my AC gremlin. I already replaced mine, with my new dryer. Leave the new dry plugged up, until you're about to pressurize the system.

Just my two bits,
~Junior

Sent from my SM-G892A using Tapatalk
 

ToxicDoc

Veteran Member
Joined
Mar 1, 2018
Location
Virginia, US
TDI
2001 Jetta, S7, .216
that's about all you can do. Other questions include why is the system empty? Do you have a vacuum to remove the air, moisture, and check for leaks? and the recommendation to change O-rings and dryer is a good idea.
 

red16vdub

Veteran Member
Joined
Aug 26, 2013
Location
(617) City of CHAMPIONS
TDI
03 JSW 5spd
Not really.

But if it has no charge then odds are there is moisture damage and the compressor is shot. The dryer definitely needs to be replaced any time the system is depressurized for more than a very short period of time (an hour or so).

Obviously the first thing is to find the leak; highest odds are the shaft seal on the compressor but it could be anywhere. If you don't have a refrigerant sniffer a can of refrigerant with UV dye and a black light will find it fast -- just don't use the stuff with sealants in it.

If the AC system is depressurize for an hour you need to replace the receiver dryer .
This is simply not true.


Bajan
 

09wingates

Well-known member
Joined
Apr 2, 2017
Location
Texas
TDI
2002 Beetle ALH Manual
So I charged the system and got two cans in. According to the tag under the hood that’s just about all it holds. The compressor and fans kicked in like a champ and blew cold air. So far I don’t have any leaks down but we will see how it is in the morning. To answer the zero charge question, I bought the car without the ac working. I hit a deer last fall and had to swap radiator condnesor etc from a parts car. I just now got around to diagnosing the ac system to find the issue. In the back of my mind I know I probably have a leak but I am hopeful I don’t. Thanks for the advice
 

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
Ah well if you changed the condenser then obviously you had to depressurize the system! :)

If you did not evacuate the system (pull a hard vacuum on it) first then you have trapped moisture in there that WILL eventually get you. The problem is that the refrigerant + moisture forms an acid and eats the system from the inside out. It's one of the "gotchas" with 134a systems; there cannot be ANY moisture (which has other bad effects in all systems anyway, including freezing up the TXV or evaporator's interior tubes, which is why it was considered "ok" in the trade-offs when 134a was designed) in the system or it will eventually be destroyed.

Replacing the evaporator is a five-alarm pain in the butt (same as heater core replacement; the entire dash has to come out of the car to get to it!)

Assuming you just charged it and didn't pull vacuum (I presume you don't have a vacuum pump) I'd take it to an AC place, have them fully evacuate it, replace the dryer and pull vacuum on it for a solid hour first, then recharge it. If you have reason to believe there's a slow leak then use one can of refrigerant with UV dye and one without so you can easily find it when it leaks down some.

SOME of the dryer dessicants used cannot be renewed. There are plenty of people who believe if you pull vacuum on a dryer for a good long time all the moisture it trapped will be released and removed. Maybe, maybe not depending on the exact dessicant in there, so unless you *know* whether the particular one in question has a dessicant that undergoes chemical change (as opposed to simple absorption) you have no way to know if it's ok to do that or not.

The other problem with the dryer is that it's a fairly decent filter for garbage (sludge, etc) that accumulates in the system over time. They can and DO plug up; a partially plugged one will materially lower cooling efficiency by serving as an orifice in front of the TXV and a really badly-plugged one will make the system inop entirely (with very low high-side pressure.) Since they're also cheap it's poor economy to not change it any time the system is at atmospheric pressure. The only bad thing with changing it is that on the MkIv cars it's a five-alarm pain in the butt to get to the mounting bolt for the clamp and the top bolt for the connection, and you have to be careful with that top one too because it's directly connected to the hard-line of the condenser output. Fracture that pipe and you're now tearing the front of the car off and replacing the condenser.

You can detect a partially-plugged dryer by the fact that the pipe on the bottom (the output) will be cooler than the one on the top (input); there should be no material difference in temperature between them.

The capacity on the sticker is 750g with an error of +50; 2 cans is 680, so you're reasonably close to a full charge and it should work fine with that amount in there. If you want to be right in the middle of the error band put another 100g in from a third can.
 
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09wingates

Well-known member
Joined
Apr 2, 2017
Location
Texas
TDI
2002 Beetle ALH Manual
You are correct I didn't have any way to pull a vacuum on the system. So far this morning the system worked perfect and almost froze me out on the way to work. I will probably take it to a shop that can pull a vacuum and check for leaks. Since it didn't leak all the way out overnight I am hopeful its not something too serious. Time will tell but having cold air is a must since it will be triple digits down here in Tx this week.
 

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
Yeah, take it to the shop since it was at ambient pressure and have them both pull a vacuum on it and change the dryer, then recharge it. They may ***** "no warranty!" (probably will, in fact since they're not checking anything else) but do it anyway; it won't cost much money (basically the price of the refrigerant + a dryer and at most an hour of labor) but if you don't odds are good in a year or so you'll be wishing you did.
 
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