[Benjamin]

AC Issue - 2002 VW Turbo Beetle (not the S Model) – The symptoms are:
• Compressor isn’t coming on (BTW, I replaced the compressor/cluth last year, brand new Behr)
• No cold air and little electrical anomalies like erratic engine idle, or high engine idle, or an occasional sputter.
Here’s what works:
• I tested both cooling fans; they’re fine and operate together
• the 3 fuses on top of the battery tested okay too – additionally, I cleaned them with 320# and reseated them; also, I cleaned (the best I could) the contacts wherein those fuses seat.
• R134 checked okay
This may help the diagnosis:
A mechanic tested my new/1-year old Behr compressor; he says power is only getting to it intermittently. He pulled off the connector to the compressor, and put a probe in the socket (grounded to the negative battery terminal). The probe lights up for a split second, then goes dark for 4 or 5 seconds, then repeats)

Any thoughts?

 

[jfoj]

Search around on the net, I recall there may be some issues with the compressor switch on the dash??

Also note the compressor switch does not latch in in certain positions for the vent. Also the fan has to be on at least the lowest setting.

Does the compressor control switch in on the dash light up?

Also maybe one of the pressure switches on the freon lines is bad or had a bad connection?

 

[Benjamin]

The dashboard AC switch lights up yellow when depressed; and yes, the fans are on when running these "tests"

How does one check the pressure switches on the freon lines?

Lastly, if I put power directly from the battery to the compressor (bypassing everything) should it come on?

 

[Benjamin]

For what it's worth, I should mention, that I drove from NY to FL (about a month ago) and the AC worked for the entire trip, but seemed to "weaken" over the last few weeks. In other words, it didn't abruptly stop working.

 

[jfoj]

First thing I would check for sure is it there is enough Freon in the system.

Most newer cars have AC line pressure switches that control the fans and compressors. If the Freon pressures get too low, the compressor will likely short cycle.

Many of these pressure switches are not just switches but actually can put out a signal that is proportional to the line pressure so sometimes you cannot just bypass them.

Yes, power directly to the compressor clutch should engage the compressor, but do not run it a long time as the fans may not function.

I do not have a wiring diagram handy so I cannot offer much more info at this point.

Not sure on these cars if the outside temperature sensor under the bumper can impact the AC operation, but I know on BMW's if the outside temp sensor is broken, missing or the wiring is damaged then the AC may not work properly.

Does your car shop appropriate outside temp on above the inside mirror?

You may need a tool like VCDS from Ross Tech to properly verify the pressure sensors??

See info below in my signature.

Also verify that the serpentine belt routing is correct. Its a bit tricky to route the belt correctly on the 1.8t motor. Not sure this is your issue, but should be an easy check.

 

[Benjamin]

Not sure what the freon readings should be on the hi & low sides.... Can someone post these figures please? I understand your point about proportional pressure - makes sense!

No temp reading on any mirrors

Serpentine belt is new and installed properly

Thanks!!!

 

[esse10]

cycling

Sounds like the compressor is cycling and symtoms of when it's low on Freon or perhaps it's difective compressor? was the compressor a rebuilt model from your local parts store? if so most of those are junk. good luck man

 

[Benjamin]

Compressor was brand new - Behr

 

[Benjamin]

Compressor was brand new - Behr

 

[jfoj]

Most, but maybe not all models have an outside temp display. On my car, a 2003 convertible, it is located inside the car over the rear view mirror next to the clock.

On many cars, if the outside temp sensor or wiring is damaged it can impact the AC performance, Not 100% this is the case with the Beetle? Sensor is located near the bottom of the bumper on drivers side. Many time lower bumper is damaged and sensor can get damaged.

 

[Benjamin]

Thanks, it pays for me to tinker with this sensor (or have someone test it). Thanks for the tip!

 

[obwielnls]

These are not the easiest to diagnose. There is a fan control unit that seems to be a common issue and to test the pressure switch (Actually a pressure transducer)you need a meter that reads duty cycle.

Bill