On my 2008 Vauxhall Astra 1.9 CDTI my AC Compressor has gone

I was wondering how easy it is to replace myself? I'd get the system drained at a garage first.

I've included the service instructions but I'm not sure how easy it'd be. I've never worked with an AC system before and this would be the hardest job I've ever done.

Any advice for doing this please?

Do I really have to cover the connections? How would I do this as I don't have any special tools just a socket set?

up vote 2 down vote accepted

Legally handling refrigerants requires expensive tools and in many countries it also requires a licence. However, when the refrigerant has been removed from the system and correctly stored, the physical installation and lubrication process of a compressor never requires any licence at all. So, if someone who can legally handle the refrigerant part agrees to do only that part and let you do the rest (few people would do that, unless you're friends), then there's no problem. However, getting the serpentine belt off may be hard and require special tools.

That said, the real complexity of the process depends upon how the compressor has failed and what type of compressor it is. When it's a clutch equipped compressor, if the only defective part is the clutch coil (for example, defective clutch coil thermal fuse) or clutch assembly, then replacing these is not so hard. The hardest part may be getting the actual parts, unless you source them from a second hand compressor. As a side note, in that lucky case, if you want to do a real pro repair, then, after you're done with the clutch replacement and before you install the compressor back on the car, find the oil drain cap on the compressor body (on a Delphi CVC, by the way, it's a hexagonal bolt located on the under side of the compressor, right next to the pulley end), remove it, drain the oil into a graduated container (help the draining process by rotating the compressor shaft as the oil drains) and pour PAG 46 ac lubricant oil (modern piston compressors require this type and viscosity of oil) into that drain hole, the same quantity of oil that you drained out of the compressor obviously (provided your system hasn't leaked any up to that point), then replace the cap seal and close the drain hole. A charge of fresh oil won't hurt for sure. Make sure you're using double end capped PAG oil so that you won't need to worry about moisture while handling the oil. Then, when the compressor is on the car with the refrigerant lines connected, and before it gets charged with refrigerant, rotate the clutch hub with your hands 10-20 times to push any excess oil from the compressor cylinders. If easy to do, leave the clutch coil wire unplugged until the AC system gets charged with refrigerant, so that the compressor won't engage no matter what you do until you want it to.

If the compressor has seized, then the system has to be flushed. Not so easy. In that case, once the flush is done, the full oil charge will need to be fitted inside the compressor. I'd recommend a pro do the compressor job in that case. A new condenser will be needed too, since parallel flow condensers, the ones on modern cars, are nearly impossible to flush.

If the compressor is clutchless, the compressor's shaft shall never be turned by the engine until the system is charged with the full refrigerant charge, or the compressor will immediately seize since nothing is moving the oil around the system and the compressor can easily pump out anything left inside its crankcase, especially if the engine is revved out of idle. Again, i'd let the pro do the whole job to avoid any nuisances.

In any case, a receiver dryer/dryer replacement is always required when the system is left open for any amount of time. It's always better if it's fitted right before vacuuming the system and charging it with refrigerant, by whoever is handling the refrigerant part. Hand him/her a sealed spare dryer/receiver dryer and ask him/her to fit it for you.

Yes, if you can, always cap the refrigerant lines. PAG oil, unless it's the double end capped type (and you won't really know what oil has been fitted into your AC system), is hygroscopic. If the only missing part in the system is the receiver dryer, then if you have the "metal pipe/canister" type receiver dryer try to cap/seal the open connections (and tell what you've done to who is handling the refrigerant part).

Changing compressor is pretty easy on your car, however you have to go and fill it at some car shop. Your compressor is on the top of alternator, so it's easy to access and take off. If I remember correctly 3 bolts are holding it then disconnect the hoses and you are good to go.

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