Alternator wire: size/grade

Going to upgrade the wire from alternator to fusebox, do I also need to upgrade anywhere else? i.e. from fusebox to ... ? Not sure what the output is, alt is a Lucas from a 260 so thinking to go with 10mm-square wire / 70A. Sound reasonable? (Electrical idiot speaking) cheers Bill

The critical path is the alternator to the battery. Your alt may be a 55A in which case a 70A cable would be OK. However if the 260 had AC it may have had a bigger alt as well in which case the 70A may not be enough. I don't know the order things are connected but I doubt the fusebox will need such a hefty feed itself especially as some items are ignition switched. You only need to upgrade other wiring if you upgrade or add other components in the car. Having said that adding relays into the headlamp circuits can improve light output dramatically according to some who've done it. How did you mount the alternator? Andrew

Looking into it more I think I see now. B+ to starter terminal is one to watch like you said. Because of the route I'd assumed it went via the fusebox but I guess not. I'm not adding any load apart from a radio so I'm forgetting about other upgrade/replaces. I'd also assumed the alt would be always putting out it's rated output, but seems not so. So apart from the right length 3/8 bolt I'm good to go... Cheers for your help.

Cheers, it's a 60s or poss very early 70s one so hopefully not much of a strain. Good thing is it has a "U" channel which is FM so can be used with the MP3 and FM transmitter, so no need for CDs 'n that, cheers, Bill

What about the regulator? 

Have no idea of which altenator you are retrofitting, but for a long time, all altenators had a seperate regulator. Eventually they changed to integrated regulators. Did you collect the regulator with the altenator, or get a confident assurance that the unit has an intergtated regulator? If not, sort this out before running the unit. Either way, you will need to add additional wiring for the regulator. Output cable for the altenator should be 70A capacity as suggested and should run directly from B+ output terminal to either the battery terminal or the battery cable terminal on the starter, whichever is shortest/most accessable. Don't worry about cabling back to to the fuse box, and then to battery or starter. Make sure that the altenator is properly earthed to the block, directly via mounting brackets or via an earth cable. Some 240 brackets are rubber bushed for vibration and won't provide an earth. Other Volvo brackets may be also so it is worth checking. Was the car originally configured with an altenator or a generator/dynamo, and positive or negative earth? These factors also ned to be considered in the conversion.

Thanks for that malb, but all is accounted for. I chose an alt with an integrated reg, and the car is neg earth. Also the alt is mounted direct to the block and will have a separate earth wire as well. cheers, Bill