An Extra Wire... Please Help!!

[NardisCNC]

Hi, I'm a newbie here and to MG's in general. I just bought a 66 Midget a few weeks ago. And already I'm stumped having to ask kindly for assistance from the more knowledgeable minds on this forum.

Yesterday, I had to take off my starter to free up and lubricate the little gear that didn't want to engage. After fixing it and putting the starter back on. I found a single loose wire, and I don't know if it was attached or not before. Although I don't think it was attached. I don't know if I may have accidentally pulled it off.

My car (66 Midget) has been switched over to the Negative Ground system, and an Alternator has been installed in place of the generator. Currently the Alternator has 3 terminals on it, and only 1 wire coming off of it. Is that normal? There wouldn't be 2 wires would there?

I'm assuming that wire was from the Generator before, and is not being used now. Could that be right?

Also, I read online somewhere that 1-wire alternators don't charge until they are revved up. Is this correct? That might also explain why it didn't charge the battery at all after jumping that car and letting it idle for 10-15 mins. (I accidentally left the lights on earlier in the day).

The mystery wire (red/yellow) is a larger gauge wire than the one that is currently connected to the alternator (red/green). What else is confusing, is that its about the right length to reach the alternator and the spade connector is also of the larger type. I don't have a wiring diagram for this car yet. Any thoughts on this. Thanks in advance for any help!!

I look forward to meeting some of you this summer!!

Nardis

 

[regularman]

There should be another wire coming off the alternator going to the idiot light in the dash that tells when you are not charging. If this wire is not hooked up then it might not charge at all. Most alternators use this idiot light wire to excite the alternator and make it start charging. Basically its a light that is run between the battery and the alternator output. When the alternator is putting out power then it and the battery are the same voltage and the light does not light, but if the alternator is not charging then it gives 0volts (or ground) on that wire and the battery wire still being 12 volts the light lights up. This 12 volts is felt through the light and gives the alternator a bit of power to get started when you first start the car. I would suspect that other wire goes to the alternator.

 

[Pythias]

You say red/yellow and red/green. The book shows BROWN/red, BROWN/green go to the generator. .. both these should be going to your alternator. That heavier gauge wire should be your charging circuit. The other end should lands on "D" of your voltage regulator. The Brown/Green lands on "F". Hanging around the same area should be a White/Brown. It normally would land on the oil filter mounting and is the dirty oil filter warning light wire. It may actually be still landed

 

[jvandyke]

Wires schmires, that's one great look'n Midget!!

 

[DrEntropy]

I think you'll find that larger wire IS a brown/yellow one. It is part of the charging circuit, would have been on the generator output originally... Don't know what alternator you have, but the wire should be on the output.

The "Advance Auto Wire" website hasn't a Spridget diagram BUT: the MGB wiring is nearly identical and can illustrate the way it was originally rigged.

 

[Trevor Jessie]

There are a collection of diagrams here:
https://www.spridget-tech.com/page2.html

 

[NardisCNC]

There should be another wire coming off the alternator going to the idiot light in the dash that tells when you are not charging. If this wire is not hooked up then it might not charge at all. Most alternators use this idiot light wire to excite the alternator and make it start charging. Basically its a light that is run between the battery and the alternator output. When the alternator is putting out power then it and the battery are the same voltage and the light does not light, but if the alternator is not charging then it gives 0volts (or ground) on that wire and the battery wire still being 12 volts the light lights up. This 12 volts is felt through the light and gives the alternator a bit of power to get started when you first start the car. I would suspect that other wire goes to the alternator.

I think you hit it right on the head!! And I was wondering what that "ignition" light was in the first place. That has to be what that extra wire is.

Now I have to figure out.... which of the 2 remaining Alternator terminals does it go to?? How do I go about this? I could not see any markings on the alternator. Can I do it with a Volt-meter referencing them to ground (with the engine idling) and see which one is putting out voltage? If that will work, will they both be putting out voltage, or only one??

Thanks SO MUCH for everybody's help!!

Nardis

 

[regularman]

Find out what brand of alternator it is and google for the wiring on the internet. I don't want to give advice on something I can't see for myself. You sure there are not any mrakings on it?

 

[Sarastro]

Your picture seems to show a heavy wire disconnected, correct? The alternator's output is a heavy wire and the one to the ignition light is thinner.

Look at the alternator terminals that have no connection. Probably they are connected together; that is, the double tab is really a U-shaped piece of copper. So, if this is what came loose, and it is indeed a u-shape, you can connect to either terminal.

Now, MOST alternators used in these cars, even upgrades, have a heavy wire to a 3/8" tab and thinner one to a 1/4" tab. you can't trust wire colors, because they may have been changed wwhen the alternator was installed. I'm reluctant to tell you just to sock the wire onto the terminal, because there are other arrangements (rarely, I'll admit) and I don't know for sure what you have. Good point to have someone who knows these things look at it to be sure.

BTW look in the Wiki general tech section for an article on alternator upgrades. You'll see a little better what's going on.