Originally Posted by Mister Two

I have recently had success upgrading the original RS Air conditioning compressor to a 2006 Impreza AC compressor. So I thought I'd let you guys know.

Overall the system is lighter by about 5-6Kg since the new pump and bracket is all alloy compared to the mostly cast steel of the RS pump and bracket. Most noticeably is reduced power drain on the engine when driving. My old AC pump made the car feel like a gutless pig when it was on. The new one is much better. You can still feel it when its on, but the power drain is massively reduced.

In the cabin, the temperature of the air when the AC first comes on drops a lot faster and seems to maintain very cold temps better even on high fan output.

To do this the parts you need are:

- 2006 AC Pump
- Alloy Mounting Bracket and small steel brace that sits on the other side of the compressor
- Late model AC belt tensioner
- 2006 AC Hose fittings that connect to the compressor
- Late model AC belt guard

It all bolts into place with the new lighter Alloy bracket and new belt tensioner. The original RS hoses even line up perfect with the 2006 Pump, but alas the diameter of the fitting is too small and wont seal. It is NOT recommend to use an over size o-ring to make up the difference.

You need to remove your original AC hoses and take them with the new AC hoses to get them adapted at somewhere like Pirtek or Enzed. Basically they cut off the ends of the RS hose fitting and weld on Late model ends. Or you can get completely new hoses made up with the new end fittings. I paid $90 to have this done.
The 2006 top fitting has the filling valve on it. It needs to be cut off and the hole welded over so that it doesnt hit the bonnet.

Remove the original wires that attach to the RS AC pump. The wiring for the electronic clutch needs to be cut and joined to the RS wires so the pump becomes plug and play. The RS pump has a over temp switch. The new one doesn't. So you just bypass the over-temp circuit by shorting the plug that normally plugs into the temp switch.

Gas it up and its good to go.

Things to note:

Its a good idea to change the receiver dryer when you change the pump. They absorb moisture in the system. I paid $27 for one at Repco. Only swap out the receiver dryer just before you gas it up. Otherwise it will begin to absorb moisture from the atmosphere.

And when you are re-fitting the hoses. You need to get some new o-rings for the end fittings and make sure they are oiled so they don't dry out and leak later on.

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