1975 Wagon, 440 mostly stock charging system not working.

[DC118us]

Hi all,

I haven't posted in a while, but I recently upgraded my fuel system to a sniper efi. That all went well, but my charging system is no longer working (it seemed to be working last summer). Here's what I've done so far. Had the alternator tested and repaired (it wasn't charging), replaced the regulator and still nothing. I find there's NO POWER to either the field on the alternator or the violet w/white stripe wire at the regulator. Car starts and runs fine. Trying to read the wiring diagram is confusing (electrical not my forte). I see that power to those 2 locations should be supplied by ign 1. I have power at the ballast resistor on the firewall, regulator is grounded, alternator is hooked up just as before I touched it. I'm at a loss on where to go from here.

Any ideas on what I'm missing? I looked at the 2 fusible links I find (one near battery and one on passenger fender near alternator) they look fine, not burnt or discolored.

Oh, I also jumped the field tab on the alternator to the positive power post on the alternator and it did NOT begin charging either.

 

[68NewportSportVert]

You should have blue and green wires to the field on the alternator. Blue should have power from the ignition switch. The green wire supplies a variable ground to vary the alternators output.

 

[DC118us]

My car has what looks like a tan wire from the vr and a dark green wire. The alternator has a violet w/white stripe wire to one field and dark green to the other. Neither the tan on vr nor violet/white stripe on alternator field has power. There’s power at the positive post of the alternator but that appears to be the only power.

 

[Big_John]

Oh, I also jumped the field tab on the alternator to the positive power post on the alternator and it did NOT begin charging either.

It won't. The field is controlled by the negative.

Here's how you test it.

Take a voltage reading at the battery just for reference, car not running.

Disconnect the green wire from the alternator and make a jumper wire that goes from the connector on the alternator to a good ground.

Turn on the headlights on high beam and start the car.

Check the voltage at the battery again. It should be 14-15 volts at minimum. If it's not, there's a problem with the alternator. If there is, the problem is either the voltage regulator or the wiring to the VR.

Don't run the car for long like this. Just long enough to check voltage.

This duplicates the FSM procedure except you are using the headlights to load the battery rather than the carbon pile. What we are doing is bypassing the VR to perform the test. The VR controls the alternator by completing the circuit in the field by grounding it.

 

[DC118us]

It won't. The field is controlled by the negative.

Here's how you test it.

Take a voltage reading at the battery just for reference, car not running.

Disconnect the green wire from the alternator and make a jumper wire that goes from the connector on the alternator to a good ground.

Turn on the headlights on high beam and start the car.

Check the voltage at the battery again. It should be 14-15 volts at minimum. If it's not, there's a problem with the alternator. If there is, the problem is either the voltage regulator or the wiring to the VR.

Don't run the car for long like this. Just long enough to check voltage.

This duplicates the FSM procedure except you are using the headlights to load the battery rather than the carbon pile. What we are doing is bypassing the VR to perform the test. The VR controls the alternator by completing the circuit in the field by grounding it.

Ok so I’ll give that a try, groundling the green wire field tab. Does the other wire need to be connected still or is it ok if it’s disc as well during this test?

 

[Big_John]

Ok so I’ll give that a try, groundling the green wire field tab. Does the other wire need to be connected still or is it ok if it’s disc as well during this test?

The other wire has to be connected.

The field is actually one continual "wire" that connects on one side to switched +12 volt power and the other end to the VR. You are bypassing the VR by doing this.

 

[DC118us]

The other wire has to be connected.

The field is actually one continual "wire" that connects on one side to switched +12 volt power and the other end to the VR. You are bypassing the VR by doing this.

Ok, then one side of the field would have to be powered, right? Along with one side of the vr. Neither of the field wires have power and neither of the vr wires have power in run.

 

[Big_John]

Ok, then one side of the field would have to be powered, right? Along with one side of the vr. Neither of the field wires have power and neither of the vr wires have power in run.

With the key on, there should be power from the blue wire. There also should be power (again Key on) from positive feed wire (not sure of color on a '75) to VR.

AGAIN, you won't have power from the VR to the green wire to the alternator.

If you don't have power, there is an issue with the wiring.

Do you have a Factory Service Manual (FSM)?

Here's how this works... Very simplified version. See the blue wire? That gets positive 12 volts from the ignition switch. Again, not sure what the color is to your 1975 VR (I don't have that FSM)

When the voltage dips, the VR grounds the green wire to the alternator field. This makes the alternator charge the battery. The test eliminates the VR, making the alternator go into full charge.

If I were a betting man, I'd bet on you've disconnected or cut a wire while installing the EFI.

 

[DC118us]

With the key on, there should be power from the blue wire. There also should be power (again Key on) from positive feed wire (not sure of color on a '75) to VR.

AGAIN, you won't have power from the VR to the green wire to the alternator.

If you don't have power, there is an issue with the wiring.

Do you have a Factory Service Manual (FSM)?

Here's how this works... Very simplified version. See the blue wire? That gets positive 12 volts from the ignition switch. Again, not sure what the color is to your 1975 VR (I don't have that FSM)

When the voltage dips, the VR grounds the green wire to the alternator field. This makes the alternator charge the battery. The test eliminates the VR, making the alternator go into full charge.

If I were a betting man, I'd bet on you've disconnected or cut a wire while installing the EFI.

View attachment 585729

Ok this all makes sense with what I was expecting. I need to back track to try and figure out why I have no power at either the vr or field wire. Also not sure if it’s related but I don’t currently have low beams or dash lights. So something has definitely changed since last summer. Totally odd behavior electrically. Thanks for the assistance

 

[DC118us]

Ok this all makes sense with what I was expecting. I need to back track to try and figure out why I have no power at either the vr or field wire. Also not sure if it’s related but I don’t currently have low beams or dash lights. So something has definitely changed since last summer. Totally odd behavior electrically. Thanks for the assistance

Big John! You were 100% correct. I did disconnect something to route my fuel line along the firewall and didn’t reconnect it! I went back through everything and found this, with both plugs disconnected. Thanks again for the help. Turned out to be a loose nut behind the wrench! Lol

 

[mrfury68]

IIRC that is the field load relay used only on 75 & 76 models. Always a good idea to re-trace your steps of your most recent work.

 

[thethee]

IIRC that is the field load relay

You do remember correctly, I have the same on my 75 imp

 

[DC118us]

IIRC that is the field load relay used only on 75 & 76 models. Always a good idea to re-trace your steps of your most recent work.

I believe you must be right. That got power to my vr and alternator field. Plus it must feed dash lights and low beam headlights too.

 

[Dan Scully]

IIRC that is the field load relay used only on 75 & 76 models. Always a good idea to re-trace your steps of your most recent work.

Is this used on only higher output alternators? What is its function? Thanks

 

[DC118us]

Is this used on only higher output alternators? What is its function? Thanks

Unfortunately I don’t know. I only know when it’s disconnected the car won’t charge.

 

[Big_John]

I didn't know about the field load relay, so I went looking.

Learned something new!

They cover it from 2:00 to about 4:40.

 

[mrfury68]

Is this used on only higher output alternators? What is its function? Thanks

Used on all applications 75-76 IIRC. I had a '76 Cordoba that had charging issues, luckily I also had a good friend who was a Chrysler/Plymouth mechanic and he pointed me in the right direction. Not sure of its function but when the relay stuck closed you weren't charging.

 

[Two 67's]

Used on all applications 75-76 IIRC. I had a '76 Cordoba that had charging issues, luckily I also had a good friend who was a Chrysler/Plymouth mechanic and he pointed me in the right direction. Not sure of its function but when the relay stuck closed you weren't charging.

Eddie?

 

[mrfury68]

Eddie?

Yep. I have learned a lot from him over the years. Great mechanic and even better person.