Voltage regulator problem with 1968 Dart

[MrBelvedere2]

Ok first of all yes I searched the forum and found some information, but this situation is unique.

background:
1968 dodge dart with a 440/727
New M&H wiring harness in the engine bay
Original Harness under dash in very nice shape
Battery relocated to the trunk
Brand new Battery
Brand new alternator, dual field converted to single with one terminal grounded.
Brand new Voltage Regulator
6ga continous wire running from the alternator to the trunk

Here's the problem.

The car does not want to charge I installed a new Alternator and Voltage Regulator
when you turn the key to Accessory position, the voltage regulator gets fried and smoke comes out.
I checked the voltage at the blue wire coming into the voltage regulator, 12.4 volts

I also noticed the the car is also blowing the fuse for the cigar lighter/dome light.
cold these 2 thing be related?

The car starts up and runs but it's running off of the battery.

From what I looked up already most of the diagnosing and running jumper wires assumes the battery is still in engine bay.

I looked at everything for anything obvious(blown wire,melted wires,mouse eating wires, shorted to ground, etc.)

Any tips you guys have for me? The car ran fine and charged fine and did not have this problem before it got parked indoors and the motor rebuilt.

thank you

 

[Demonic]

Brand new alternator, dual field converted to single with one terminal grounded.
Brand new Voltage Regulator
6ga continous wire running from the alternator to the trunk
Here's the problem.

The car does not want to charge I installed a new Alternator and Voltage Regulator
when you turn the key to Accessory position, the voltage regulator gets fried and smoke comes out.
I checked the voltage at the blue wire coming into the voltage regulator, 12.4 volts

Something is wrong in the regulator circuit. Does the new M&H harness match the original harness removed?

 

[67Dart273]

You for sure have someting wong VERY first thing I'd look at is a ground between the VR and field and or grounded field

I assume? you are still using the older style single terminal field alternator?

The older system has one field terminal and the remaining brush is grounded. So if you check resistance from the field terminal to the case, it will be quite low resistance, BUT NOT zero or full short. It is VERY common on isolated field alternators to find one field terminal grounded, that should not be

Next disconnect the green field wire from the regulator and from the VR. It should be zero resistance from one end to the other but open to ground. Believe it or not, we had a member here with one grounded--shorted, to ground.

 

[MrBelvedere2]

yes it is the original style single field wiring harness.

I am using a new dual field alternator since thats what you get at the parts store now, with 1 field grounded.

 

[Mattax]

Sounds like that was done correctly.
Do the checks 67Dart273 suggested. Don't need the battery connected.

Not sure why the 6 gage wire goes from alternator to the battery in the trunk.
Simplest method for battery in trunk is battery positive to starter - but larger than 6 because of the distance- then 8 or 10 gage up to the starter relay.
Everything else is factory and will work and trouble shoot same way.
(this is assuming no kill switch.)

 

[MrBelvedere2]

there is a kill switch, its wired with the ford style solenoid to the battery cable is only hot when cranking the car. the alternator cable has to go to the kill switch to cut power to whole car if the switch gets turned off, to pass NHRA Tech inspection.

 

[Mattax]

OK. That's prob not directly related then.
How does power get to the main splice? The reproduction harness heavy black wire?
Is ignition using points or something electronic? And if electronic - how is it wired?
I ask that because the original regulator shares the ignition circuit.

when you turn the key to Accessory position, the voltage regulator gets fried and smoke comes out.

This should be a pretty big clue.
Key in RUN should let power flow through both 'ignition 1' (run) and accessory feeds out of the key switch.

I checked the voltage at the blue wire coming into the voltage regulator, 12.4 volts

What key position when you measured this?

I also noticed the the car is also blowing the fuse for the cigar lighter/dome light.
cold these 2 thing be related?

Could be.

The dome light circuit is always hot. It doesn't go through the key.

Have you noticed when the fuse is blowing?

 

[MrBelvedere2]

OK. That's prob not directly related then.
How does power get to the main splice? The reproduction harness heavy black wire? Not sure which wire your talking about, the one that would normally go to the BAT stud on the alternator? That one is Shrinkwrapped and taped off.

Is ignition using points or something electronic? And if electronic - how is it wired? MSD Ready to run distributor with no box, MSD Blaster2 coil wired per MSD directions
I ask that because the original regulator shares the ignition circuit.


What key position when you measured this? When the key is in ACC position


The dome light circuit is always hot. It doesn't go through the key.

Have you noticed when the fuse is blowing? The fuse blows the second the kill switch gets turned on and providing power to car

 

[67Dart273]

^^Your questions seem off track here^^. What have you checked in the alternator / field circuit. So far as the main splice, it is illustrated very well by the MAD electrical article

Catalog

Catalog

The splice is up under the dash a few inches from the ammeter in the big black ammeter wire. Power comes from the starter relay big stud---fuse link--through firewall--to and through ammeter--to welded splice. From there it branches off NOTE that there is NO fuse protection except for the main fuse link, and that is poor protection. I got to witness an entire underhood harness smoke in the early 70's because of a diode that fell down inside the alternator, and THEN the link blew

Nothing in the power feed TO the VR should hurt it. It is most likely on the LOAD side of the VR which is the alternator field and that circuit. And be sure the VR is GROUNDED

The power path to the alternator field is ignition switch---through the firewall--to whatever splice is in the dark blue "ignition run." This varies by year. From there, the dark blue feeds ignition "run", the VR power, electric choke if used, and any smog devices under the hood. None of that could smoke the VR. It is a power feed You CAN however, smoke IT, because the "run" line is NOT fused other than the main fuse link, and that is darn poor protection.

I tell you again. Check the field to alternator case for resistance, check the green wire for shorts, and check the VR for being grounded.

 

[Mattax]

How does power get to the main splice? The reproduction harness heavy black wire?

Not sure which wire your talking about, the one that would normally go to the BAT stud on the alternator?

H'm. This is important so lets look at the stock wiring for minute.
The car has two power sources, alternator and battery. The factory wired them together at the main splice. The main splice is where all of the other circuits are tied in except the starter motor. Whether the alternator is providing power or the battery is providing power, power goes to the main splice and then wherever needed.

So if the alternator output is cut and taped, and the battery feed/charge connects to the alternator, this is what I'm picturing.

That can't be right. It's connected somewhere.

 

[Mattax]

What key position when you measured this? When the key is in ACC position

So there was power available in the RUN circuit (ign 1) with the key in Accessory position.
There shouldn't be.
My suggestion is to disconnect the battery and do continuity checks rather than measuring voltage.

The fuse blows the second the kill switch gets turned on and providing power to car

Normally that would be a short in the wiring. Either the cigar lighter or the dome light feed wire is touching ground.
Disconnect the battery. Measure for continuity between the fuse terminal and the body ground.

MSD Ready to run distributor with no box, MSD Blaster2 coil wired per MSD directions

Doesn't help us much. Where does the RTR distributor connect?
Where it was connected may or may not relate to the VR letting out smoke.
But start here, whith what 67Dart273 has suggested a couple times. Its the right place to start looking.

I tell you again. Check the field to alternator case for resistance, check the green wire for shorts, and check the VR for being grounded.

 

[MrBelvedere2]

thank you for the help and suggestions! the diagrams are pretty much right as the car has a dedicated charging wire going to the trunk to the kill switch.

I will print this out and do some checks like suggested. I will try to get out there this week and update you all.

thanks again for the help

 

[Mattax]

Let us know what you find.

I sketched a couple possible ways it might be set up that would work.
This is one, but it uses the original alternator output wire.

 

[MrBelvedere2]

thank you very much taking the time to sketch up some diagrams. Should be helpful!

 

[MrBelvedere2]

Ok, here is an update on this thread.

Here is a diagram of the way the car is wired with the battery in the trunk, except instead of a 1 wire alternator it is using a factory alternator and VR wiring, you can see how the feed wire is the wire that feeds the car from the trunk to the starter relay then the main feed goes to the "welded splice" connected on one stud on the ammeter in the dash.




I check resistance in the places you suggested, all seems good and is what you described.
I made a mistake and said it fries the VR when it's in ACC postiion, i meant to say in the RUN position before you turn the key to crank.
I also added another ground wire from the body of the regulator to a good ground just make sure it's grounded.
I also took the alternator in and had it checked just to make sure it was good.

The MSD ready to run distributor is a 3 wire connection, 1 ground, 1 to negative side of the coil and 1 to the positive side of the coil.
I eliminated the ballast resistor as the MSD distributor needs a full 12 volts to run.

Where the car is right now, everything is good, I put a new FBO solid state VR in the car but afraid to turn the key for fear it's going to fry the new one.
Appreciate the help so far.

 

[67Dart273]

How the rest of the car is wired has little or nothing to do with frying a regulator. THE ONLY POSSIBLE WAY to fry the old style regulator is "something shorted." ---And I mean right there in the field circuit, which I told you in an earlier post

The circuit path for the old style regulator is ..............switched power to the IGN terminal......through the regulator (which MUST be grounded)........out the F terminal on the green wire.........to the alternator field........through the field.........to ground.

If the green field wire OR THE FIELD ITSELF is shorted you will either smoke the regulator or pop the internal link in the OEM mechanical ones.

How do you check this? EASY Should take you about 2 minutes

YOU NEED a decent multimeter. Disconnect the green field wire from the VR and from the field. Check the continuity to ground. Should be open/ infinity.

Next put the ohmeter on the low ohms scale, "Hard" squeeze the probes together and notice the reading. Should be very very low, "point" something which is the internal resistance of the system and probes. This is the "zero" or "dead short.

Now "stab" one probe hard into the alternator case. The other, probe the insulated field terminal. Read the resistance and attempt to get an accurate reading. Those fields draw "around" 4---to a max of 6 or so amps, so ohms law "says" that a 4 amp field should read about 3 ohms. If you get a reading of less than one, or "point" something inspect the brush holder for shorts/ missing insulating hardware. It also might be that the actual field itself is shorted.

 

[MrBelvedere2]

Thank very much for the help, in tracing the path like you suggested 67Dart273, I found that the field in the alternator itself was shorted and causing the regulator to fry. Even though I had it checked and it was supposedly good. got a new alternator, new regulator (FBO ignition solid state) and it fired up putting 14.4 to the battery.

Thank you everyone for you help.