How to read Duty Cycle %

[JustCruisn]

I'm having AC problems in my GTI.

I've narrowed it down to the pressure sensor. I actually replaced it as I found it was not sending a signal to the AC fan control module.
Well the new one does not seem to be sending a signal either.

Basically the sensor needs to send 20-90% duty for the controller to turn on the compressor.
Since I have replaced it and still no signal I'm now doubting my ability to test for duty cycle correctly.

What is the correct way to do test with a digital multimeter?
The sensor has 3 pins.
12v+
Signal
Ground

I've been testing across ground and signal and get a flat 0%
I've been following this DIY
Fault diagnosis in the Fan Control Module - Gtivr6wiki

[Transporter]

The duty cycle is the length of time that the circuit is ON or OFF.
ON time may refer to either high or low portion of the waveform that depends if the circuit is power side or ground side controlled.

So, when you said 0%, I understand it as that the circuit is OFF, since most automotive duty cycle specs refer to circuit ON time.

To test the duty cycle, you need the multimeter that has the duty cycle mode. I recommend SXE Probe, if you going to buy the duty cycle meter and already have good multimeter. Or better still get cheap hand held oscilloscope.

[h100vw]

Where in Brissy do you live. Probably dead easy to look at it with VCDS. I am in Wooloowin/Clayfield if you want to come over tomorrow arvo.

Gavin

[JustCruisn]

The duty cycle is the length of time that the circuit is ON or OFF.
ON time may refer to either high or low portion of the waveform that depends if the circuit is power side or ground side controlled.

So, when you said 0%, I understand it as that the circuit is OFF, since most automotive duty cycle specs refer to circuit ON time.

To test the duty cycle, you need the multimeter that has the duty cycle mode. I recommend SXE Probe, if you going to buy the duty cycle meter and already have good multimeter. Or better still get cheap hand held oscilloscope.

I've got a multimeter, from **** Smith. It has Duty Cycle mode. I wanted to be sure I was using it correctly before making a conclusion as to what was wrong.

I might take up Gavin's offer for a VCDS scan, then work out what to do next.

[JustCruisn]

I worked out how to read the Duty Cycle % value from the pressure sensor.
Simply set the multimeter to Duty Cycle % (not hz) then use the positive lead on the pin with the signal.
I did this today as my AC is broken again, not the pressure switch this time though. I found it easiest to unplug the connector to the fan controller, where the signal is sent, and probe the pin there. You could also read it from the wiring loom as well.

I was able to get a reading of 27% then I engaged the compressor and the reading increased steadily. I stopped when it got to 42%, about 4 seconds of compressor time. This helped me confirm that one of the sensors I had was faulty.