Clarification on 70+ alternator VR on 68 cuda

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evans68cuda

evans68cuda

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Hey guys, I added an MSD box and am putting speakers in my 68 cuda so I decided a 60 amp should work well. I do not have AC, electric fuel pump, or electric fans. I also have Done the MAD bypass and added a 8awg wire from the alternator to the starter relay. I told the auto parts store that I needed an alternator and VR for a 71 duster 340 along with a female connector to the VR. So just clarifying, all I need to do is splice the 2 old wires from my VR to the new connector I got? I was reading a forum on here that confused me because they said you must add a wire but I don't see where, since both VRs have 2 wires coming out. Also, I'm not looking for a killer sound system, no subwoofer anything, just 4 speakers capable of 125 watts. Thanks!

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You need to add one wire

You can take the old VR wires yes and add them direct to the new one, blue to the IGN terminal, and green to the field terminal.

Hook the new alternator up just like the one..............!!!BUT WAIT!!!1

You have one more field terminal..........Run a wire from that new field terminal up and splice to the blue IGN terminal

While you are at this, check for voltage drop in the harness, which will cause OVER charging (over voltage) at the battery

Turn the key to "run" with the engine off. Put one multimeter probe on the battery POS post and the other on your blue IGN terminal. You are hoping for a very low reading, the lower the better. ANY drop there ADDS to the charging voltage. Over about .3V (3/10 of one volt) is getting to be "a bit much."

Causes are drop in the harness. The blue wire terminals passing through the bulkhead, the ignition switch connector terminals, and the contacts in the switch itself.
 
The new alternator only has 1 field terminal, so I put a piggy back blade on it? So just solder the old blue wire to the new blue on the connector and green to green? And then splice the new wire piggybacked on the field terminal to the blue wire coming off the VR?
 
Here's the 70 wiring diagram. So looks like just add a wire from the Field on the altternator into the IGN blue wire at the VR. Now can I piggyback the Field terminal is the question?

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The alternator should have 2 field terminals. In that case, You'll add a branch to the blue wire. The original connector that you'll cut off at the regulator is the one needed at the alternator so all you need is about 8 feet of blue wire, butt connectors, and hardware to mount the regulator. It doesn't mount to the same holes. It does need to be well grounded at its mounting. I added a hole and a spacer about 1/2 tall to keep the reg' in the same location. I disconnected the senders, coil, etc.., to lift the engine harness, unwrap, and add the blue wire in.
Now with a square back alternator that has only 1 field terminal, I guess you wouldn't need to add the blue wire? Just make sure the alternator is well grounded through its mounting brackets? But then you wouldn't have the isolated field like late model OEM. Your upgrade is solid state regulator and higher output alternator. I honestly don't know how much difference the isolated field makes. I did use the proper alternator and wiring for complete upgrade. I figure if I go ahead and do the same way their engineers did, I don't need to question or understand all of it.
 
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No, piggy back of the single field will make a short!
The new regulator shown in first post must be used with later two terminal fied alternator. A picture of back of your alternator would be helpful.

A single field terminal suggests you have wrong alternator. There are electronic old style regulators, and could be used with stock wiring, but really need to verify alternator to be sure.

A new two terminal field alternator can be used with early or late regulators with correct wiring changes, but a late regulator will only work with late alternator.

It s best to verify field of late style is isolated by measuring field terminals to case and check for open with Ohm meter. Also test for continuity of a few Ohms between terminals.
 
KitCarlson said:
No, piggy back of the single field will make a short!
The new regulator shown in first post must be used with later two terminal fied alternator. A picture of back of your alternator would be helpful.

A single field terminal suggests you have wrong alternator. There are electronic old style regulators, and could be used with stock wiring, but really need to verify alternator to be sure.

A new two terminal field alternator can be used with early or late regulators with correct wiring changes, but a late regulator will only work with late alternator.

It s best to verify field of late style is isolated by measuring field terminals to case and check for open with Ohm meter. Also test for continuity of a few Ohms between terminals.
Click to expand...

So the alternator he has would be used with his original regulator or a hybrid solid state regulator such as VR-128. Higher output while retaining the original closed field design.
 
KitCarlson said:
No, piggy back of the single field will make a short!
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Click to expand...

You MUST USE a 70 or later alternator with TWO field terminals AND CHECK that they are NOT GROUNDED!!! (Many rebuilds come through "incorrectly" grounded

Post a photo of the alternator you bought.....................
 
The VR regulates the alternator ground to the chassis through the case, it must have a good star washer ground chassis bond. The old style points regulated the + voltage to the alternator, and yes you must use a dual field with that E-regulator.
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Looks like I have the wrong alternator then. Pretty sure I need a 20153 which is a 60 amp with 2 field terminals. I wonder if my regulator isn't for a 60 amp then? And can I solder the new wire from the alternator to the existing blue ignition wire where it will be cut for the new connector? And what gauge should the new wire be?
 
You have the correct regulator and yes you'll splice/branch that blue wire. It's the only switched hot wire you have under the hood so...
Wire gauge? Same as whats there will work ( 18 maybe? I forget ).
 
Got the new alternator coming in tomorrow, thanks guys! Already have the new connector, VR, and the new wire spliced in and ready!
 
67Dart273 said:
I give up. Have fun
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What do you give up on? The one field terminal threw me off, sorry if that is what you are referring to, I just did not know what to do about that, was thinking maybe a piggyback blade would work but you guys confirmed why it would not, that is why these forums are so great!
 
68cuder said:
What do you give up on? The one field terminal threw me off, sorry if that is what you are referring to, I just did not know what to do about that, was thinking maybe a piggyback blade would work but you guys confirmed why it would not, that is why these forums are so great!
Click to expand...
Here, I had to go back further than I expected, but this is a previous round of the squareback /solid-state reg. upgrade.......
Going from pre-70s V Reg to the newer post-70s V Reg Squareback
 
Thanks guys! Just fired the 340 up today and it's runnin good! Charging at 14.7v at WOT, I think I'm also going to install headlight relays next
 
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