S5:Episode4-1990 Jaguar XJS Convertible Restoration/Delanair Mk3 Air Climate Control Overview.
Climate control systems, and air conditioning specifically, is a subject that many find mysterious but almost everyone wants to know more about. The Delanair Mk 3 system in the 1990 XJS convertible restoration has to be renovated so this looks like a good opportunity to do a general over view of the system and hopefully de-mystify it for you a bit.
P.S.- At the 4:30 point in the video, the 4.36 Volt reading at the green/brown clutch relay wire isn't what it should be. The reading at pin #20 from the top of the row of test pins on the ECM should read 12Volts assuming a fully charged battery. Anything less will not activate the compressor clutch. To check voltage at the ECM, test at pin #1. It is very important not to touch other pins during these tests as it can damage the ECM. To prevent this I place a short piece of the smallest chain saw fuel line on the end of the test probe to isolate the pin being tested from the adjacent ones.