Hi,
Could someone look at their S1 4.2 E-Type alternator and tell me what that Alternator 4th lug is for ? It’s an original Alt although the regulator is aftermarket. I forgot how the regulator wires go back on. I took alt to local shop and it tested good. Original factory wiring.
It’s a survival '66 that required engine/head rebuilt.
Many thanks,
Patrick
'66 FHC
That lug is for electricity to the field.
There are two field connectors to the alternator that come from the voltage regulator. One is called Field minus and one called field plus
Dennis
69 OTS
I think you are referring to the AL connection.
That is wired to the 3AW relay that controls your charging warning light.
The relay is usually mounted near the voltage regulator next to the battery.
The connector I was referring to is the one in the photo with nothing connected to it.
One of the nicest things I did for myself was replacing that alternator harness - it leads a tough life there next to the manifold and that braided insulation does not age well. Here is mine with colors showing - I couldn’t tell much about the colors on yours (maybe you can’t either):
So you’re looking for one more wire – with either a purple or green tracer. These are the F+ & F- leads and so far as I know it matters not which is connected to which on the alternator F lugs.
As for the connection at the regulator, I think there was possibly a plug there at one time that made that connection fairly fool proof.
I saved my old plug (why?) and can send it to you if you want it, though single connections work well enough once you work out who’s who.
Thanks guys,
What’s perplexing is my '66 FHC Alt harness has just three wire to Alt (B+ heavy current wire, ground wire; marked “AL”, and just one “F” field wire. Correspondly, my regulator has just three wires.
Patrick
'66 FHC
John, my '66 FHC dash warning light is connected to the oil pressure sensor. I don’t have a 3AW relay. Another oddity, my '66 FHC has its brake fluid switch mounted to the X-panel on firewall (rather than the picture frame). My Alt has an “Al” lug, and “F” lug and a “B+” lug and one mystery unmarked lug.
I see Geo '69 Etype has the 3AW relay, but my '66 FHC lacks that relay. Geo has four wires to his Alternator, I have just three. Its possible a PO installed a later 4.2 Alt but I was lead to believe car came to me as 100% original.
Patrick
'66 FHC
The alternator on my 66 has an extra lug with no wire on it. Mine does not have the 3AW.
So how do you know which is which? Or more specifically, are you sure there is a wire for the AL connection?
Jack, on your '66, which alt lug is vacant ? Where is your front brake fluid switch mounted ?
Geo, one of the alternator harness wires is long, so I assume that’s the “AL” stamped lug, the thick current screw lug is course the Alt B+, and the other wire I assume is the “F” lug, so perhaps the vacant lug should be that thick practice protected lug; perhaps a lug for those with B+ non screw wires ?
Patrick
'66 fhc
I think you may be assuming incorrectly.
The connections are similar to mine:
That plastic fitting holds the brushes and the two lugs are the connections to them (F+ & F-). Both need a wire connected.
I suspect that the wire you have on the AL terminal is really one of the F (field) leads - you can check this with an ohmmeter by looking for continuity from those wires to the wires that are to be connected to the control box.
Once that is confirmed they can be attached.
As I recall, the AL lug is an AC current that would be used with the 3AW - I do not know what or if it has any function when that relay & warning light system are not used.
Thanks George… Ill leave that “AL” stamped lug vacant; and test the two field wires for continuity; but which is field+ and field -, or does it not matter ? The face of the alternator does not show field polarity.
Patrick
'66 fhc
I believe it does not matter.
Patrick, on my car the AL lug is not connected to anything. I recall that when i had the alt rebuilt years ago i connected one of the wires to it when putting it back in and i got no charge.
My brake light switch is on the picture frame.
Thanks Jack and Geo,
There was Ohm meter continuity between the two “Field” wires to the “-” and “F” lugs on the regulator. The “AL” Alt lug will remain vacant.
Patrick
'66 FHC
Thanks Jack, I’ve seen pics of 3.8 Etype with front brake fluid switch on picture frame but for some reason some 4.2 variants (like my '66 FHC) have brake switch on X-panel/firewall.
Patrick
'66 FHC
On the pictures you posted, the field+ is the encased spade terminal and the field- is the open spade terminal.
Polarity should match the VR terminals.
Regards.
John G.
Yes, fortunately my car, built September 1965, pre-dated the change. Makes it very easy to replace it without having to bleed the brakes.
Jack
Thanks John,
I corrected the '66 FHC Alt field polarity.
Take care,
Patrick
'66 FHC
A few points:
The field connection should have two wires at the alternator: F+ and F-. They two can be reversed without problem, but the “more right” way to hook them up is for the F+ connection to be the lug closest to B+,
There is NO AL wire unless the car has a 3AW relay. On earlier cars, an oil pressure switch was used to turn on the dash light instead of the 3AW. So on your '66, the AL lug on the alternator shouldn’t be connected to anything. (If you accidentally connect the F- lead to the AL lug, you may release smoke.) If there’s a 3AW, the AL lead on the alternator is wired to the corresponding lead on the 3AW.
The three lugs on the VR are “+”, which is fed from the alternator relay. " -", which is connected to a good ground. And " F-", which is a controlled ground, an connects to the corresponding lug on the alternator. If the regulator has the fourth lug, it’s unused.
The alternator relay feeds both F+ at the alternator and + at the VR.
