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1969 MGC Alternator - Lucas 16 ACR - Wiring

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55-60MG4KM Avatar
55-60MG4KM Silver Member Keith Meyer
Corvallis, OR, USA   USA
I have read the Topics on the MGC alternators to death looking for what I think is a simple answer to my wiring question. I think I understand but would appreciate someone with more knowledge than me to confirm my thinking. My 69 MGC originally had a Lucas 16 ACR alternator on it. I have two 16 ACR's that I had rebuilt (both were dead when I bought the car) and I want to put one on the car and use the other as a spare. When I bought my MGC the alternator on the car was made by WPS and the alternator model number has long since dissappeared. The wiring going into the WPS appears to be the original 3 wire set up which I understand is correct for the 69's as mine has a later production date. There is a large brown wire, a smaller brown/yellow striped wire and a smaller blue wire. The two smaller wires, brown/yellow and blue, are connected to one another. The large brown wire is separate. They all fit in the spade going onto the back of the WPS aftermarket alternator. So, from what I have read I should be able to take the three wires out of the WPS spade connector and keeping them in the same configuration, place them in the Moss Conversion spade connector. A bit of a pause (and question) here because I really cant tell if the Moss conversion spade connector shape matches the opening shape in the 16 ACR - can anybody confirm it does? Assuming it does, there are two large spades and one small spade in the 16ACR. Obviously the two smaller wires go to the smaller spade in the 16 ACR. Therefore the large brown wire has to go to one of two large spades in the 16 ACR - but which one??

To summarize my statement and questions:
I should be able to use the exsiting three wires going to the WPS in the 16 ACR.
The two smaller wires should remain attached to one another.
If the Moss Conversion connector matches the shape of the 16 ACR connection opening I should be able to place the wires in the Moss connector.
The smaller wires should remain connected together and should be wired into the smaller connector in the Moss Conversion connector.
The larger wire should be wired into the one of the two larger connectors in the Moss Conversion connector - BUT WHICH ONE?

Enclosed are a few pictures to help (I hope) clarify my understanding. Thanks for your help.

PS: I have a 2.875" pulley i'll use. I do like the new 100+ alternators some of you are going to and would go that way if I hadnt already rebuilt the two 16 ACR's. Maybe later.

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kirks-auto Platinum Member Robert Kirk
Davenport, IA, USA   USA
Please clarify as I infer the WPS rear female connector differs from the OEM plug meant to fit the OEM Lucas ACR. I thought the Moss plug was for the early and mostly 1968 Lucas units with external regulators an AC (or "A" in the factory parts book). The "R" in ACR means internal regulator.
Here's what I found for Morris which should be the same or similar to MG, with the heavy wire on the the top and two smaller on the next lower ports/lugs.



Regards,
Robert Kirk

kirkbrit@yahoo.com
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Business phone 563 323 1017

http://kirks-auto.com/
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kirks-auto Platinum Member Robert Kirk
Davenport, IA, USA   USA
New alternator in stock shows rear plug with two large male lugs over the bottom small lug, if that is any help.

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Regards,
Robert Kirk

kirkbrit@yahoo.com
E-mail PLEASE for quote/questions/orders

Business phone 563 323 1017

http://kirks-auto.com/
Moss distributor/UK importer
Beat or match most retail/delivered quote


Member Services:
Parts for your classic British and Italian car. 30 years in business.
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55-60MG4KM Avatar
55-60MG4KM Silver Member Keith Meyer
Corvallis, OR, USA   USA
My second picture shown is the spade that goes into the back of the aftermarket WPS Alternator. This aftermarket Alternator spade configuration does not match any of the configuration openings in the 16ACR Alternator that I have. Although your schematic is helpful in understanding the wiring layout my problem reamains - I have one large spade and two smaller spades that have been combined into one connection and I have no idea where (I can figure out how to mount them) where these spades will mount on the 16ACR. Keith

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moesignguy Steve Moore
Galena, OH, USA   USA
1963 Triumph TR4 "4"
1968 Triumph Spitfire MkIII "Spit"
1969 MG MGC GT "Da C"
2005 Mini Cooper S "LARG MARG"
Hey Keith, I'm in the same situation with my 69 MGC GT. My new wire harness has five wires in four sets of wires for the alternator. The Alternator from Moss has two large blade connections and one small that use the same plug convertor as you have shown. There is a fourth blade off to the side that the plug kit doesn't meet up with.
I trace the large and small brown wires back to the starter and then to the ignition switch. Acording to the wiring diagram the brown and yellow are to go to the tachometer.
As you do, I also need to know what blade in the alternator each wire goes to. Will post if I find out.

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markmga Avatar
markmga Mark Wellard
Brisbane, QLD, Australia   AUS
1959 MG MGA Twin-Cam Coupe "Basket Case"
1961 MG MGA 1600
1969 MG MGC
Steve, Is that because the loom is for an earlier car with the external regulator?

Mark

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PETE W Sussex Peter H
Ansty, West Sussex, UK   GBR
This might help you Steve, if you haven’t found similar already. There are others if you search.

https://www.mgexp.com/phorum/read.php?1,3700448

I think you probably do have the right loom ie for and alternator with its own regulator. The two big spades should be connected in the alternator and you can put both brown wires on them or just on one - they should both go to the starter.

Two of those brown and yellows are just a loop in the loom - not very far up - you just need one brown and yellow which goes to the small spade and to the alternator warning light. I think you can ignore the standalone spade.

At least that’s how my new loom came and how I wired it, but I do have a different alternator.

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Ken Plumstead Avatar
Smithers, BC, Canada   CAN
1965 MG MGB
1968 MG MGC GT
Keith and Steve,

If you look down at the connector spades on the back of your alternators you will see the two large spades are actually one bent into a 'U' shape or similarly joined together.

Keith,

Your 16ACR has an internal regulator which makes it a two wire hook up. One large brown wire from the starter post to either of the large alternator spades and the brown/yellow wire from the tach ignition lamp connects to the small spade on the alternator. That's it, any other wires are redundant.

Steve,

In your pic you are showing us the wires ends from the regulator. I'm assuming your new alternator from Moss is an 18ACR which means it has an internal regulator and that makes it a two wire hook up. One large brown wire from the starter post to either one of the large alternator spades and the brown/yellow wire from the tach ignition lamp to the small spade on the alternator. That's it, any other wires and the old regulator are redundant.

Ken



MG: Transforming gasoline into Fun!!!



Edited 3 time(s). Last edit at 2018-11-24 12:19 PM by Ken Plumstead.

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Ken Plumstead Avatar
Smithers, BC, Canada   CAN
1965 MG MGB
1968 MG MGC GT
Keith,

I did a little more research on the 16ACR and there may be a little more to it.

Look down in the back of the alternator at the connectors where it says "IND". Is it two spades joined together or two electrically separate spades?

Ignore the "B" spade for now.

Actually a good vertical picture into the connector holes would be helpful.

Ken



MG: Transforming gasoline into Fun!!!



Edited 1 time(s). Last edit at 2018-11-24 12:38 PM by Ken Plumstead.

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55-60MG4KM Avatar
55-60MG4KM Silver Member Keith Meyer
Corvallis, OR, USA   USA
Ken: Rather than get to confusing on the forum I thought i'd send directly to you. I have taken a few pictures as enclosed. Now the more confusing part - A. The above picture shows the three wires going onto the aftermarket alternator. The large brown wire, the smaller brown/yellow wire and the blue wire. I traced the blue wire back to the instrument cluster and it appears that someone in the past replaced the wire with this blue wire. B. The original wiring loom had three other wires coming out of it but these any connectors to these wires were cut off, the end of the wire electrically taped, the wires folded back and taped to the loom. I can send more pictures. They are obviously not used, at least on the aftermarket alternator. So, do I use the three wire setup on the 16ACR and then where do they go? Or, do I need to resurrect the other three wires and where do they go? Just in case my email address is: kgm@proaxis.com and my phone number is 541-231-8487. Thanks, Keith


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Ken Plumstead Avatar
Smithers, BC, Canada   CAN
1965 MG MGB
1968 MG MGC GT
Ok, got it now.

There is more to it. Because it's an early alternator it's more than a two wire hook up.

Attached below is the wiring diagram for a 68/69 MGB with the 16ACR alternator. The MGC workshop manual, page 14.A.4, shows the same set up as the 68/69 MGB.

Connect:

1. the large brown wire from the starter post to the alternator large + spade connector;
2. an additional smaller brown wire goes from the starter post to the B+ spade connector;
3. a brown/yellow wire goes from the tach to one of the IND spade connectors;
4. connect a jumper between the two IND spade connectors.

Don't worry about the wiring for the previous alternator. Hook it up this way and 'Viola', you should be good to go.

Ken

Edit: we might as well keep going forward in this thread. Who knows someone else in the future might want to do the same as you.



MG: Transforming gasoline into Fun!!!



Edited 1 time(s). Last edit at 2018-11-24 05:56 PM by Ken Plumstead.


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55-60MG4KM Avatar
55-60MG4KM Silver Member Keith Meyer
Corvallis, OR, USA   USA
Ken: I believe I understand your directions and have enclosed a pdf of what I understand you are saying. However, i'm still confused and probably a little dense.

Connected to the Aftermarket Alternator are only three wires. These wires were wrapped in black electrical tape. These wires are shown in the "Wires Wound" picture enclosed. The three wires connected to the aftermarket alternator are: 1. The large brown wire. 2. A brown / yellow wire. 3. A blue wire. The blue wire runs loosely and by itself through the engine bay, past the firewall, across the underside of the dash and appears to be (I can't see the actual connection) connected to the alternator warning light on the dash. It is my opinion this blue wire is a replacement for the original wire to the alternator warning light that apparently has failed. Tomorrow I will run a continuity check to confirm this circuit. Finally, both the brown / yellow and the blue wire are connected to one another and they share the same post on the aftermarket alternator.

In the second picture I have unwound all the black electrical tape back to the original factory wiring loom which is wrapped in blue tape. When I removed the black electrical tape an additional three wires were exposed. These three wires were all folded back along the wiring loom, they were missing any spade connections, they had electrical tape covering there cleanly cut off wire ends and they were individually wrapped with electrical tape to keep there ends clear of any possible contacts. The colors of these three wires are: 1. A brown / yellow wire. 2. A second brown / yellow wire. These two do not appear to be connected. 3. A slightly larger diameter (but not as large a the very large brown wire) brown wire.

I now have three brown / yellow wires of about the same guage and both your wiring diagram and mine show only one brown yellow wire going to the alternator warning light. Where do these other two go? Following your wiring diagram and explanation the newly exposed single brown wire of a slightly larger guage goes to the B+ connection and the single brown wire of a much larger guage goes to the + connection.

I'll do some more checking tomorrow to see if I can figure out which brown /yellow goes where but i'm still a bit confused with the three brown / yellow wires. Keith


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Ken Plumstead Avatar
Smithers, BC, Canada   CAN
1965 MG MGB
1968 MG MGC GT
Keith,

You keep going back to the previous wiring. If it was my car I would remove all that old alternator wiring (especially potentially live wires cut and taped off) and rewire it as per the '69 MGC with 16ACR alternator wiring plan.

When you rewire, it's not essential to use brown or brown/yellow wires. Any wire of sufficient gauge will work, although using the correct coded wire will certainly help yourself and anyone that comes after you diagnose future electrical issues.

It sounds like whoever put in the current alternator just cut the old alternator wiring and then wired in the aftermarket alternator from scratch or your car may have originally had a 16AC alternator and an external regulator or both. That might explain all the extra wiring.

Ken



MG: Transforming gasoline into Fun!!!

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moesignguy Steve Moore
Galena, OH, USA   USA
1963 Triumph TR4 "4"
1968 Triumph Spitfire MkIII "Spit"
1969 MG MGC GT "Da C"
2005 Mini Cooper S "LARG MARG"
So.... I take the plastic back cover off the alternator. Kinda makes sense now. Easy to confirm that both large terminals are connected and find the the two smaller ones are also wired together. Would explain why one may need a brown/yellow wire "jumper" if they were not wired together in the alternator. I'm thinkin I wire it as a two wire system as advised above and see what I get when I fire it up. May permanantly wire both brown wires to large blades and the dual brown/yellow wires to the smaller blade with the "kit". Then put the single brown/yellow wire on the side terminal. Noted as redundent but could also see them as back up. Thanks for all the input / info ya'll.


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Ken Plumstead Avatar
Smithers, BC, Canada   CAN
1965 MG MGB
1968 MG MGC GT
Steve,

Don't overthink it or overwire it. Only two wires are required; one from the starter to the alternator and one from the tach to the alternator. That's it.

There is an example from the 71/72 MGB wiring diagram below.


I did the same set up on my '65 MGB when I installed an 18ACR in it (pic below).

Ken



MG: Transforming gasoline into Fun!!!


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