[paulgato]

Interesting thread. I have a 2002 VW golf Tdi and the serpentine belt runs the alternator, the P/S pump and the A/C compressor. I have no use for the A/C and want to junk that whole system anyway. It occured to me I could drive the alternator off the crank pulley using the existing tensioner and drive the P/S pump via a short belt with an electric motor put in the place of - or in the guts of - the old A/C compressor.

An A/C-style magnetic clutch to go on the P/S pump would be great though. A very elegant solution. The trouble is, that would take a fair amount of hunting around and measuring up and tinkering, and all with the P/S pump off the vehicle. And meanwhile, I'd have no vehicle.

I think for myself, it would make more sense to first install an electric P/S pump out of an old car, get that working, and THEN remove the old P/S pump to tinker around with it. I'm planning on running almost alternator-less anyway so running without the serpentine belt would be fine for a few weeks probably.

Another possibility is to somehow (??) fit an electric motor in the guts of the A/C compressor, but again, there is the problem of how to use the vehicle in the meantime. I think (but I don't know) that the Mk4 Golf would have been produced without A/C in some models, in which case there should be a shorter belt available. If this is the case then I could try getting a suitable electric motor to fit into the body of the compressor.

I admire the elegance of fitting a clutch pulley to the P/S pump but I can't see how I can do it realistically, so I think I'll be going down the route of fitting an electric P/S pump/motor from a Citroen C4 or Peugeot 307. This also give me the advantage that I can remove the serpentine belt entirely and save a little more fuel if I don't need the alternator. (On my daily, local routes I probably won't need the alternator, and if I get stuck, it is but the work of a moment to put the belt back on. Just need to carry the belt and a spanner in the boot.)

I'm surprised at the (maximum) current draw of electric power steering pumps though. 50A? 80A? ...people were quoting here? That's huge. It's only momentary, and I don't believe a larger alternator would be necessary. After all, you don't need a large alternator to run a powerful starter motor. But it does show how much potential saving there is to be had from going electric if you DON'T use the alternator to produce your electricity, but use the grid or solar cells instead.

If my alternative charging system becomes so good that I can ditch the alternator entirely then I can convert the alternator into a motor and use that to drive the existing P/S pump on demand via a shorter belt.

Hmmm... I still think the most realistic idea is that of fitting an electric P/S pump from another vehicle. For me at least. A simple ON/OFF switch on the dash so I can switch it off for motorway cruising and switch it back on for city driving.