Date: Sun, 2 Sep 2007 17:53:26 +0100 From: "Tim.." <the.farm.nonospam.btinternet.com> Subject: Re: [XP] Sporadic aircon
"Colin Stamp" <col.dustbinnospamp.plus.com> wrote in message news:e2mld31cksg5u6rbn1r4evvjnjel3rh0finospamcom... > On Sun, 02 Sep 2007 09:39:37 -0400, Steve B. <nonenospam.com> wrote: > >>On Sun, 02 Sep 2007 10:56:52 GMT, "Mrcheerful" <nbkm57nospamail.com> >>wrote: >> >>> >>>"Colin Stamp" <col.dustbinnospamp.plus.com> wrote in message >>>news:td3ld35g32isos1ag912fl96ktfaf9dcs7nospamcom... >>>> On Sun, 2 Sep 2007 09:38:51 +0100, "moray" >>>> <mtb_hyphen_rulesnospamail.co.uk> wrote: >>>>> >>>>>Most likely a knackered clutch on the compressor. >>>>>Connect a test lamp from the clutch power wires on the compressor, and >>>>>see >>>>>if it's still getting power when the system stops working. >>>>> >>>> >>>> Could be. The next part of my cunning plan is to check the clutch is >>>> pulling current. >>>> >>>> I'm still wondering if there might be a refrigeration problem which >>>> could cause the high-side pressure to intermittently drop to a >>>> "switched off" level even with the compressor running though. >>>> >>>> Cheers, >>>> >>>> Colin. >>> >>>moisture in the system can cause this, it freezes to form a plug, then >>>melts >>>etc. >>> >> >>But when you get a blockage in the system high pressure goes through >>the roof and low pressure drops very low (or even to vacuum if the >>switch doesn't cut the compressor off). His pressure is going back to >>an "at rest" pressure. >> >>You need to know if the compressor is turning or not when the problem >>happens. The LED is a good idea but an LED will light with virtually >>no current. A compressor clutch needs a few amps to pull it in. If >>you have a poor connection / bad switch somewhere in the loop it is >>possible for there to still be enough oommmppf to light an LED and not >>pull in the compressor. Kind of like having a dead battery... The >>interior lights will still come on but the starter won't spin. >> >> Steve B. > > I have news!. It's the clutch for certain. > > I finally managed to get the thing to fail whilst parked today, by > letting it idle for ages on the drive after a longish run. It stayed > failed when I opened the bonnet too, so I could finally check stuff > out properly. > > The compressor isn't turning even though there's 15mV across its fuse, > which is the same voltage as when the syetem works properly and the > compressor is on. So the clutch is definitely pulling normal current, > but it isn't engaged. > > Right. Now I need to fix the bloody thing. A quick Google suggests > that I might be able to fix it by taking some shims out to compensate > for the wear. I suppose the next step is to take the clutch apart and > see if that's possible. > > Anyone done this on a 9-3 before? No, but I bet its similar clutch to a Volvo 70 series, which also need periodic re-shimming when the air gap becomes too great for the magnet to pull in the clutch. You'll be needing a clutch puller to do it. Tim..
