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It seemed appropriate that I should pick the hottest day of the year to point my 928 towards Wiltshire, where Richard Armstrong had kindly offered to diagnose my problem of aircon which had worked wonderfully in past, but now barely cooled and was impotent in face of current hot spell.
I try to keep the hvac in good health electrically and vac-wise. I knew everything was fine in that sense, so was pretty certain that I was just low on refrigerant. Clutch was engaging compressor, no vac leaks, recirc flap closing, sight glass on dryer was not helpful though - I could see flickering as refrigerant flowed, but not the bubbles I thought were symptomatic of low gas. For once those dreaded words in for sale ads "aircon just needs a regas" might have some truth.
The complication was that my 91S4 had never had aircom conversion, and was still running on the now banned (since 1993!) R12. There was no record in the service history of this ever being recharged.
Richard first connected various pressure gauges and lines, and from the readings confirmed that refrigerant levels were low, but not low enough to trip low pressure switch. As R12 can no longer be used, the system had to be converted to R134a.
This is where Richard's huge experience of refrigeration in general and 928 aircon in particular is invaluable. He first completely evacuated the system of the remains of the old R12 and the mineral oil used in conjunction with the old gas. He then changed the low and high pressue fittings from R12 type to R134a (no mean feat in a hot engine bay - they are really awkward to get to and manipulate), introduced the correct amount of synthetic "PAG" oil, then connected a cylinder of R134a to charge the system from scratch. Though he monitored the weight of gas introduced, he actually interpreted the pressure gauges to decide how much to add. Just blindly adding a certain weight of gas risks over-pressuring system and causing a leak. Richard has also found that a recharge is best done on 928s by running the aircon to pull the gas in.
As soon as the right pressure was reached Richard used a temp probe to confirm the system was delivering the right temp drop (the outside temp was 30C, and the probe measured 14C at door vent). But even without benefit of temp measurement the cabin was deliciously chilly. I could really enjoy the drive home with the system blowing ice cubes, and one happy owner is now looking forward to the summer's trips and shows (I had a particularly hot and sweaty trip back from Lichfield show a couple of weeks ago, and that was before the heatwave had started).
We're lucky to have a brilliant guy in Richard to lean on for aircon help and expertise, especially as he fits it in as a labour of love alongside his real profession. If you just need a standard R134a regas, a conversion and charge like mine, or have more serious aircon problems then I can't recommend Richard strongly enough. Don't hesitate whatever the distance (it was a 2 hour drive for me and I realise a lot further for others) - Richard knows 928 hvac better than anyone else
In the country which ultimately saves you time/money. As with the other stalwarts who support our cars including Paul A and John Speake, it's just a pleasure spending time with them and an education to see them at work.
Richard runs one 928 and races the other, so sorry guys he only works on 928s! As well as aircon he can iffer various exhaust options too. The guy is a real engineer - we're talking 3D CAD - so you can be sure parts he has designed/fabricated will be top quality.
Keep that heatwave coming! The 928 has superbly effective aircon when everything is sorted.
Adrian
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928 S4 Amazon Green 91MY
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