Thread: Help with air con

Help required with aircon.

replaced clutch on the 97 300tdi discovery series 1. just wondering if the connector at the aircon unit for the clutch assembly should always have 12v even with no key in ignition? Removed relay from drivers side foot well and still 12v present at connector C145.

Problem is the coil for the clutch is constantly energized

Accordin' to my 92,000.5 page factory electrical manual (the dog ate the other half a page if you must know), the compressor clutch relay is supplied with power via the ignition load relay every time the ignition is turned on. The A/C clutch circuit is then completed (ideally, only when you decide you want it to be) via about a thousand manual and automatic switches in the clutch coil relay earth line.

It seems you have a workshop or factory manual, so you probably already know that, but if I may continue to think aloud for a bit:
1) if you've removed relay K108 and it's still got power, there must be an inadvertent connection to +ve via the black/green wire that goes to the relay socket - unlikely in my books - or
2) via C217 to the 30A Fuse 3 in the engine bay - also unlikely, as that would require a short across the relay socket, or (and this is where my hard earned is going)
3) there's an inadvertent misconnection along the spare wire that goes from join S295 (the 3 way splice in the black/green (BG) wire that goes from C145 to the clutch relay (K108) base, thus:

That spare wire is in the harness for those high falutin' types who can afford dedicated air conditioning in the rear for their corgies, poodles, mothers in law etc, and is worth a careful check to see if you've accidentally plugged something a bit skewiff whilst fiddling with your clutch.

That BG wire should go to pin 6 on connector C216 (6:C216) > BG to 14:C212 > BG to 13:C448 > BG to 1:C464 (the spare connector that the rear A/C water valve would get plugged into, if'n ya had one), then stop. I can't help thinking you may have accidentally plugged something into C464 while you were down there.

Anyway, I get the impression that you have a circuit manual, but let me know if you need the colours and locations of those pesky ole splices and connectors. And I've found also that the colours or locations of the relays aren't always as they're supposed to be, so it's worth making sure you get the right relays etc.

I trust this is helpful, or at least that I've impressed everybody with my suave interpretations of the Machiavellian workings of the dear old Disco's electrical rats nest. Cheers.