TR6 71 TR6 Alternator Connections

[kevinpfrancis]

Hi folks-
I'm trying to determine how the wiring works on my alternator, as the number of connections on the alternator do not align with wiring diagrams for a 71 TR6 as found here: <a href="https://www.advanceautowire.com/tr2506.pdf" target="_blank">https://www.advanceautowire.com/tr2506.pdf

The diagram shows 5 connections on the alternator.

My alternator has 4 connections.

I have 3 wires (NW, NY, NR). I think I may be missing a ground? Is this needed?

My trouble is, which wire hooks up to which connection on the back of the alternator? The location of the connections on the diagram do not align with the connections on the alternator itself.<br>
Photo of diagram and the alternator itself attached.




Thanks!!!

 

[TexasKnucklehead]

The ground is the case. It is bolted to the engine, so doesn't actually have/need a wire to make that connection.

Welcome to the forum.

 

[TRopic6]

Hi Kevin,

Looks like you have a 3-wire alternator, which came along later. See the 73 diagram. This was a common replacement back in the day (and now) so possibly your wiring harness has already been modified to the 3-wire plug.

Also, it looks like the top 'warning lamp' wire (small terminal) is bent downwards. It should stick straight out like the larger prongs. BTW, the two larger prongs are actually connected to the same + terminal inside the alternator. Ground is through the case as TK points out.

Jeff

 

[kevinpfrancis]

Thanks Jeff. This is great info. Knowing that the two larger prongs are actually both connected to the same + inside eliminates my confusion around why there is no wire to connect to it. Based on this info, it appears that I have everything in place that should be there.

Much appreciated!

 

[kevinpfrancis]

Jeff-
Can you clarify when you said the top 'warning lamp' is bent down... are you referring to the one above the two larger prongs? Or the one off to the side by itself?
I ask as when I got the car from the PO the warning lamp wire (NY) was connected to the prong off to the side by itself. The prong above the two larger prongs had brown (or brown/red) wire going to a split box, with one wire to the fuse box, and the other to the starter.

I'm really just looking for clarification on which wires get connected to where on the alternator. 3 connections (1) NY to warning light, (2) NW to ammeter, (3) NR to starter/fuse box.

Thanks again!
-Kevin

 

[dklawson]

I don't presume to speak for Jeff but I believe that he is referring to the small spade terminal in the group of 3. It appears to be bent. That will make it difficult to use the wiring harness 3-terminal plug (if you have one). Above and below are all relative terms.

I'm including a link below to a picture of a generic 3-terminal alternator and harness plug. It shows the terminals you need to worry about. The small brown/yellow wire goes to the small terminal in the group of 3. The heavy brown wire goes to either of the large terminals in the group of three. That's all you need.

https://www.mgbimages.uk.gridhosted.co.uk/images/altplugv8.jpg

 

[TRopic6]

Hi Kevin,

I would have said what Doug said - except it was past my bedtime!

The small terminal by itself to the side was used on early 3-wire units to provide 'battery sensing' via a small brown wire. At some point it was no longer needed as the internal regular was altered somehow. I have one with a 1974 tag with that terminal and one with a 1977 tag that does not; both are 17ACR alternators. Does yours have a Lucas ID plate?

Does your harness still have the 2-piece alternator connection? I'm not sure how to make the connections for your situation. Moss used to have a kit with instructions on how to modify it to fit a newer alternator; maybe its on their website.

Jeff

.

 

[dklawson]

The small terminal by itself to the side was used on early 3-wire units to provide 'battery sensing' via a small brown wire. At some point it was no longer needed as the internal regular was altered somehow.

The 3-wire alternators replaced the earlier 5-wire setup. On the 3-wire alternators, the small terminal is used to energize the field coils when the alternator shaft starts turning. With 3-wire Lucas and most early Delco alternators the charge warning light must be in place and functional for the alternator to start charging.

With the 3-wire alternators the two large terminals are connected as stated above. One was used for the sense circuit, the other provided the power output. Generally the sense circuit does not require an external connection on the 3-wire alternators. In some applications without the ammeter a second heavy gauge brown wire is connected from the sense terminal to the starter solenoid. This splits the current between two wires instead of using just one.

 

[TRopic6]

Kevin,

Yes, the small terminal above the larger ones should have the NY wire connected to it. I can't tell if your harness connections have been modified to work with a 3-wire alternator. The early type of "3-wire" alternator had an additional small wire connected to a terminal over by the 'S' in Lucas. I can see your alternator has that terminal but not sure what wire you should connect to it. Here is how my 17ACR alternator connects up; it is original to the car and was made in mid-1974.

Jeff

 

[kevinpfrancis]

Kevin,

Yes, the small terminal above the larger ones should have the NY wire connected to it. I can't tell if your harness connections have been modified to work with a 3-wire alternator. The early type of "3-wire" alternator had an additional small wire connected to a terminal over by the 'S' in Lucas. I can see your alternator has that terminal but not sure what wire you should connect to it. Here is how my 17ACR alternator connects up; it is original to the car and was made in mid-1974.

JeffView attachment 54767

Jeff... THANK YOU!!!! This is what I have been looking for... someone with the same alternator as me. Looking at your photo, it looks like mine. Difference being that mine does not have the white plastic harness, but the wires are plugged into spade connections on the alternator itself.

From looking at your photo, the NY wire is connected to the small spade connection in the set of three as mentioned above. Assuming this runs to the lamp in the dash.
Then you have a heavy gauge brown. On mine that goes to the ammeter (which your '74 won't have).
Then you have a smaller gauge brown. On mine that goes to the the starter and fuse box.

I have no idea if this has ever worked on my car, as when I got it from the PO all the electronics have been a mess. I'm going to give it a shot wiring things up similar to yours.

Also, from looking at https://www.advanceautowire.com/tr2506.pdf, and from what you are telling me, it appears I do not have original alternator. :frown-new::frown-new: