Alternator upgrade AC11 to modern A127 type

PeterZRH

Well-Known Member
Hi folks, anyone want to check my process for swapping these? The newer type have internal regulation (no more relays) and better output at low speeds.

Disclaimer: Use this at your own risk. If your car explodes/catches fire that's your problem not mine.

ISOLATE THE BATTERY

1. Isolate the alternator relay control circuit at the 6RA relay:
Disconnect and make safe the brown wire to C1 from +12V permanent
Disconnect and make safe the white wire to W1 from +12V ignition

2. Disconnect the field control from the 11AC
Disconnect the brown/purple field + control wire
Disconnect the brown/green - control wire

3. Physically replace the 11AC with the A127.
Disconnect the brown +12V battery wire
Disconnect the brown/yellow indicator light wire.
SWAP THE ALTERNATOR
Reconnect the +12V connection
Reconnect the brown/yellow wire that was to AL to the IND terminal

4. Bridge the 3AW Ignition Light relay.
Connect the yellow wire to the brown/yellow wire (inline spade connector should do it).

RECONNECT THE BATTERY
3500-series-1-wiring-alternator-swap.jpg
 
In this vein, is it correct that an 18ACR can be replaced by an A127 without any wiring changes? Except maybe a large output wire on the B+ post?
thanks
 
Further info.

You need:

1. This type of connector - a Lucas/Bosch "B" alternator block 1697627007525.png1697627025048.png

2. The retainer clip! 1697627498966.png

3. The correct wiring. The two big terminals are in fact one and the same output. You can use the existing wiring for one side. I would recommended 2 runs of 8-guage AWG wire. If you look at real world implementations then these are often surprisingly thin - look to be 12 gauge on GM trucks for example! This is because maximum output over short wires is usually OK to be in excess of the rating for short periods of time. In reality your alternator will almost never kick out much more than half its rated output. Most of the time it'll be no more than 10-20amps. When you do your own work I'd recommend you adopt the highest, safest standards as good or better than OEM. Remember wire ratings for a certain gauge are often for a single, copper conductor, not the multi-core flexible type you will be using, which will be less. You can run the second wire to the large terminal on the starter or the terminal block on the floor of some cars, or the shunt on cars with an ammeter - for that you'll need a 1/2" spade which can be tricky to get. the Ring type connectors are easy to find something that will work but obviously make sure the size allows enough transfer contact. Silicone insulate wire is desirable over PVC as it handles heat better. Not essential though.
 
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My alternator is wired to the post of the floor. I glued some insulation around the post to provide a little additional protection from accidental short circuit.

1697627716347.png
 
I made a little "pigtail" on the small connector in the large terminal block so I could attach the original wire to the 3AW without cutting anything....
In fact in all this change, no original wire of connector was cut. This is 100% reversible should anyone yearn for a crappy charging circuit!

1697628244748.png
 
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I isolated the original 11Ac wiring with heat shrink and these are safely tied bac. I chose not to use the original power cable. The thinking for this was that I could use it for an electric power steering pump (it doesn't fit the V8)

1697628342856.png
 
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