AC problems in TDI

Trapper

Trapper

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Joined
Aug 5, 2006
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2,878
Can anyone help me with my TDI. The compressor keeps going on and off, and when I put a gauge to it the pressure goes up to 110 psi when its off and 45psi when it starts to cool, its nuts. I put a thead in at the TDI.com and the responce I got is the condensor might be good but the compressor,drier, and pressure switch need to be replaced because it what happened to thier friends car. Thier has to be an AC tech in here somewhere.
 
I am an ac man first thing to try is washing out the condenser. The low side pressure you describe is normal sounds like the high side is probably getting to high and causing the compressor to cycle. If that doesnt get it straight then you have a restriction somewhere in the system. More than likely the metering device. This is either an orifice tube or and expansion valve. Hope this helps.
 
So I shoud vac the system and flush the condenser, then maybe check the expansion valve. SOme one told me that they have heard of the compresor in the tdi to crap out on them and trash the system, I never worked on little car ac, just big trucks mostly. Everything is kinda cramed in thier. I was planning on selling this car, but I can't sell it like this.
 
Thats what i would do. The compressor will do that when is goes south inside it fills the system with metal. its kind of hard to diagnose without being there. Do yo know what the high side reading is?
 
No I don't have a fitting for the high side. but I could here in a few weeks. I have a bunch more tools back in Texas where I will be in the middle of august. I hope it hangs in thier for a while.
 
I hate to say it but its probably going to get exspensive. Did you take a garden hose and wash out the condensor?
 
I didn't think about washing out the condenser yet. I can install most of the parts myself, it just sucks to put in this money and then sell it or trade it in soon. I will see if my neighbor has a gage for the high side. Its just weird that it runs normal when going down the road most of the time, and the when you stop for a few minutes it goes in and out? I was hopping it was just a sensor.
 
i had a car do that before and it was a can low on freon and then after that its was ice cold,
 
Yea but the way the pressure reading 110psi on the low side I would be afraid of this thing blowing.
 
Mine has a problem with the AC whenever the outside temp is less than 70 degrees it won't turn on. Whenever the you push the AC button on the dash the compressor will turn on for about 3 seconds and then kick off. As I drive, and the air warms up as the day goes on, it will kick on.

Is this the same problem you are having?

Are the fans coming on when your compressor kicks on?
 
No the fans aren't turning on when the ac comes on, only one of them comes on not both. But would that effect the low side pressure?
 
Both fans should come on and then the compressor will kick in.

My wife's '00 Jetta TDI recently had AC problems as well. It turned out to be the fan switch (also known as a thrust sensor) - it usually has a 3-wire connector on it. The fan switch was actually allowing refrigerant to leak out AND it wasn't doing it's job of informing the other components that there was enough pressure in the system. The switch is an easy swap (~$65 at the dealer) and is mounted back by the firewall on a schrader valve - so when you replace it, you don't loose any refrigerant...a WISE move on VW's part I think. I replaced the switch, added refrigerant and now the AC works really well.

There is also a fan control module mounted under the battery - this could also be bad. Be sure to check fuses as well - there are more than one that could affect the AC operation as well as the radiator/condensor fans. If the fans don't come on - the compressor won't come on.

Here are the fuse identifications (since the little card provided on the fuse panel is useless) for a '98+ New Beetle, '99.5+ Golf/Jetta/Etc.:

MKIV FUSE LIST
1. Washer nozzle heaters, glove compartment light, memory seat control module (10A).
2. Turn signal lights (10A).
3. Fog light relay, instrument panel light dimmer switch (5A).
4. License plate light (5A).
5. Comfort system, cruise control, Climatronic, A/C, heated seat control modules, automatic day/night interior mirror, control module for multi-function steering wheel, control unit in steering wheel ( 7.5A).
6. Central locking system (5A).
7. Back-up lights, speedometer vehicle speed sensor (VSS) (10A).
8. Open
9. Anti-lock brake system (ABS) (5A).
10. Engine control module (ECM): gasoline engine (10A); diesel engine, Model Year 2000 > (5A).
11. Instrument cluster, shift lock solenoid (5A).
12. Data Link Connector (DLC) power supply (7.5A).
13. Brake tail lights (10A).
14. Interior lights, central locking system (10A).
15. Instrument cluster, transmission control module (TCM) (5A).
16. A/C clutch, after-run coolant pump (10A).
17. Open.
18. Headlight high beam, right (10A).
19. Headlight high beam, left (10A).
20. Headlight low beam, right (15A).
21. Headlight low beam, left (15A).
22. Parking lights right, side marker right (5A).
23. Parking lights left, side marker left (5A).
24. Windshield and rear window washer pump, windshield wiper motor (20A).
25. Fresh air blower, Climatronic, A/C (25A).
26. Rear window defogger (25A).
27. Motor for rear windshield wiper (15A).
28. Fuel pump (FP) (15A).
29. Engine control module (ECM) gasoline engine (15A); diesel engine (10A).
30. Power sunroof control module (20A).
31. Transmission control module (TCM) (20A).
32. Injectors: gasoline engine (10A); diesel engine (15A).
33. Headlight washer system (20A).
34. Engine control elements (10A).
35. 12 V power outlet (in luggage compartment) (30A).
36. Fog lights (15A).
37. Terminal (86S) on radio, Instrument cluster (10A).
38. Central locking system (with power windows), luggage compartment light, remote/fuel tank door, motor to unlock rear lid (15A).
39. Emergency flashers (15A).
40. Dual tone horn (20A).
41. Cigarette lighter (15A).
42. Radio (25A).
43. Engine control elements (10A).
44. Heated seats (15A).

Fuse arangements in fuse bracket/battery:
S162. Glow plugs (coolant) (50A).
S163. Fuel pump (FP) relay/glow plug relay (50A).
S164. Coolant fan control (FC) control module/coolant fan (40A).
S176. Relays panel interior (110A).
S177. Generator (GEN) (90 Amp.) (110A).
Generator (GEN) (120 Amp.) (150A).
S178. ABS (hydraulic pump) (30A).
S179. ABS (30A).
S180. Coolant fan (30A).

Beers,

Matt
 
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