Just when i needed it on the first warm period of the year my HVAC insisted on blowing hot air. I fiddled with all the controls but could not obtain anything but heat. Hey ho, windows open all the way to Edinburgh.
Had a re-gas which showed it was down by about 25% but held a vacuum for over 10 minutes and no trace of dye anywhere.

Worked fine until it didn't 3 days later. Exactly the same problem. This time I took more notice of what was happening leading up to it. After an overnight stop the HVAC worked perfectly for a couple of weeks. Same problem again after a few stops, engine off and re-start, same as the previous occasion.

Thought it had to be a sensor or control issue so removed the control panel. I was hoping for a load of gunk, dust etc disappointed to find very little. Cleaned out with alchohol and air including the temp sensor.

Worked great until today after a few stop starts. This time I had the opportunity to get the GAPIID onto it. Unfortunately I couldn't get it to read the HVAC ECU, so frustrating. The Ac pipes at the bulkhead were very cold and had condensation on them but still couldn't get cold in the cabin.

Once home I updated the GAPIID. The HVAC had sorted itself out and I couldn't repeat the symptons. Pressure between 1700 and 2000. Cabin temp was showing 25.2 which it clearly was not and it didn't come down much even when the cabin was very cold but it still blowed cold air (and hot when dial was moved). Compressor clutch was shown as off throughout even when requesting (and delivering) cold air.
Moving both controls from cold to hot gave appropriate responses and it settled at 22 degrees with the controls on auto, fan responded properly.

Is that pressure too high.
Is the cabin temp thermistor faulty and can it be changed.
Why was the compressor clutch always off, does that indicate a Can Bus failure rather than any problem with the compressor given the continued cold air.

Any help with this much appreciated. 2007 3.6 TDV8
1979 Mini Special
1988 Yamaha FJ1200
!952 BSA Gold Flash

You could have an intermittent electrical problem on the compressor clutch. You can power up the clutch with a permanent feed which will engage it to run all the time. If that gives you AC on demand then you know to look at a wiring or clutch pressure switch issue.

Thanks. I'll give it a go. 2007 3.6 TDV8
1979 Mini Special
1988 Yamaha FJ1200
!952 BSA Gold Flash