Change from 11ac to 18acr, is it a good idea?

Barten

Active Member
#1
My old 11ac alternator needs an overhaul. I wonder if changing to a new 18 acr is easy to do. I know I do not need the regulator 4 TR, but do not know how to rewire. Has anyone done it and how?
Regards, Barten
 
#2
Yes, easy enough to do. You need to find the 3AW warning light control unit (aluminium can looks exactly like a flasher unit) on a series 2 it is located behind the drivers glove box near the door. From memory you unplug it and join the brown/yellow to the brown/black (I think it's brown/black, it is the warning light wire from the 11ac alternator) The pulley on the alternator is smaller than the 11ac, so you will need a shorter fan belt. You will have to change the Large ring terminal that supplies the battery feed to the 11ac for a large spade, and that's you done !:)
 

roverp480

Active Member
#8
Just thought of another item, make sure the correct wattage warning light bulb (12V 2.2 Watt) is used . Alternator may not charge otherwise, as the warning light circuit energises the field coils.
 

Barten

Active Member
#9
Thank you guys, I have talked to Geoff and he has offered me a bracket as well. How close to the radiator will an 18 acr on the correct bracket sit? The reason I ask is that my old 11 ac sits very close to the radiator cowl today so if will sit more forward it will interfere. I do have an SD1 engine in my car. May be that has something to do with the tight fit.
 

harveyp6

Well-Known Member
#10
How close to the radiator will an 18 acr on the correct bracket sit? The reason I ask is that my old 11 ac sits very close to the radiator cowl today so if will sit more forward it will interfere. I do have an SD1 engine in my car. May be that has something to do with the tight fit.
It won't sit any further forward, it sits out to the side. It can't be further forward as the pulley has to be in line with the crank and waterpump. The Sd1 engine won't make any difference either, they're all the same block and heads sizewise.
 

Barten

Active Member
#11
Now I have received my new 18 ACR alternator. These are the wires. Now what goes where? Here is the alternator. I guess the cars that came with it has a contact from the wiring. 20190302_181001.jpg 20190302_181127.jpg
 

roverp480

Active Member
#12
Thick brown/ white wire plugs to one of the large Lucar terminals on the centre aperture on the alternator , Thin brown yellow to the smaller Lucar terminal next to the large ones . tape the other two up out of the way. You then need to disconnect and join the brown yellow and probably brown black ignition warning light relay wires at the ignition warning light relay . This connects the warning light straight to the alternator which wont work properly without this connection. One could get the proper plug if you want to tidy it up Lucas/Bosch Alternator Plug but use existing if you want to be able to keep original wiring to revert to 11AC at a later date
 

roverp480

Active Member
#14
If you are not confidant I would ask an auto electrician to do it., as I also wouldn't want you to short something out. Do you have the part number for the alternator?
 

Barten

Active Member
#15
No, sorry I don't have the part number on my new alternator. It is a new one I got from Wins. Anyway, due to work commitment I needed to go away for a week, so I did not have time to fiddle more with it, but I will next weekend. I will study the wiring diagram thoroughly first, I will ensure all is correct with the starter motor connections.
 

roverp480

Active Member
#16
My Rover P6 2000/2200Workshop manual shows both the 11AC and the 18ACR wiring diagrams so you should ,if you have one, be able to follow the routing. You shouldn't need to touch the starter motor wiring at all.
 

harveyp6

Well-Known Member
#17
You should be able to use the 18ACR plug in loom, then just join the two wires that aren't the earth on the 3AW to get the light working and fit the ring connector to the starter solenoid battery in terminal.
 

Barten

Active Member
#18
Today I finally connected my new 18 acr alternator to my 3500s. I followed the directions from roverp480 and Harvey. It worked perfectly. The output on the battery with the engine on was 14.4 V, and about 14.0 V with the light on and the electric fan. That is ok numbers, is it not? Thanks for your help guys!

ATTACH]13362[/ATTACH] 20190314_213406.jpg

Regards Barten
 
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