68 Charger alternator wiring

[Charger68Rick]

As I try to sort out some things on my 68 Charger with a non numbers matching 318,  I pulled the alternator to have it checked out. It did test bad so I started researching a new one. Most replacements show only the BATT terminal and the  plus  (+) FLD terminal being used. My old alternator had the negative (-) FLD terminal with a makeshift wire that was piggybacked over to the windshield washer motor ground. Is that necessary? Shouldn't the alternator just ground to the block with no need to use the negative(-) FLD? The positive (+) FLD does run to the voltage regulator which I believe is correct. The Batt lead is a double connector with one wire going to the battery and the other going to the horn relay. Is that correct also? I didn't see a BATT wire going to the horn relay in my schematic. Last question is the alternator normally a single or dual pulley on the 318?

[Nacho-RT74]

That’s the “revised” squareback alt version ( used since late 70s )  which gets like all the squareback alts ( earliers too ) both fields isolated. 68s got originally the roundbackt alt with grounded field/brush ( attached straight to the case with no isolation mount and no prong). There are also roundback dual isolated fields versions used on 70/71.

The revised squareback alt is also a bit thicker than previous alts. This can be an issue on some engines/years mounting.

These dual isolated alts are made to work on original single field setup cars ( up to 69 ) just grounding one of the fields (either one). That will replicate the original single field setup. It can made with a jumper wire and terminal between prong and chassis ground, or also replacing the isolation washer underneath the attaching screw with a metallic washer. If making this last just be sure you DON’T PLUG the field wire coming from regulator there because if you do, will short out as soon you put the key in RUN. This circuit doesn’t have fuse protection, and still if the fuse link blows, it will take an enough amount of time to burn some wiring around.

When making the grounding with a washer method, is better to clip off the prong, or bent, or cap it off with tape or shrinking tube, just to warn no field wire must be connected there…. For safety.

You could also upgrade to dual field system. It requires just the proper regulator, regulator plug and a new wire added between reg and alt

Single or double pulley? Double pulleys are for A/C cars. Hemis also used ( for whatever reason ) double pulleys too.

And yes, up to 69 where the horn relay was mounted on radiator core support, there is a violet wire between relay and alt stud attached to the alt wire. Diagrams? Depending on source you can get a 100% fiability diagram… or not.

[Nacho-RT74]

On a side note, I’m not sure if you still have both isolation washers on field prongs… the one pointing up on pic ( the one at a side of the stud ) seems to be metallic?

[Charger68Rick]

Thanks for the great info. I think I will just get the alt with the single FLD (in the pic)and eliminate the chassis ground that is piggybacked to the washer motor. Do you see any downside to that?

[Nacho-RT74]

For correctness I'd do that too.

However, most of these alts don't put out enough load at idle which is the main problem charging systems got on Mopars. If you are able to get a HiPo alt into the stock single field alt would be GREAT. Your charging system will be gratefull with that move.

[Charger68Rick]

Will do!

[Nacho-RT74]

Some alt able to source AT LEAST 40-45 amps at idle. More for the better, but AT LEAST that. Most of stock alts barely source out that at max output barely giving 20-25 amps at idle. A 40-45 amps alts are rated usually around 80 amps max output.

Smaller pulley as posible too.

I know aftermarket brands offers 90-110 and even more amps alts on stock cases ( Tuff-Stuff, Powermaster ), but most of them are built into double field setup since the single field adaptation to retrofit into older setups is pretty much simple (as described previously).

[375instroke]

My FSM shows the wire from the alternator output going to the horn relay with a note saying Coronet only.  Strange.  Coronets got some special high power horn needing full alternator output?  I'd personally run a short ground wire directly to the alternator, or ground by removing the isolation washer, making sure the brush is located in the same position after.

[mike337]

A slight variation on the above scenario.

I have a 69 Charger, and just installed a new M&H engine compartment wiring harness that leads to the alternator.

This harness has been modified by M&H to incorporate the wiring needed for an electronic ignition. I also have installed a new Powermaster alternator.

Since the new alternator has no leads for field wires, what is the correct thing to do with the blue and green wires that are in the new wiring harness?

Mike

[mike337]

Some additional information for the preceding post:

I have backed myself into a corner by changing out several electrical components on my 69 Charger, with a stroked 440 6-pack engine, and would like some input from board members.
In an attempt to upgrade several components while restoring the car, I find myself with the following:

1.   I purchased a complete custom serpentine system that included an AC compressor, PS pump, and alternator. The alternator is a Powermaster 8-67100 single wire model which has an output of 75 amps at idle, and 100 amps at higher rpm. This alternator includes an integral regulator.

2.   I also purchased a new M&H harness HU197BM for an electronic ignition modified system with an updated alternator (This harness is normally for a 440 engine without a 6-pack).

3.   I also plan on bypassing the ammeter in the dash, and will be using an aftermarket Auto Meter voltmeter in the dash.

Additional info:

I talked with M&H before buying the harness on why this harness was not appropriate for a 6-pack engine, and it came down to 5 wires.

A.   Since the normal coil placement on a 6-pack engine is to the right rear of the manifold, the two coil wires in this new harness (for a front of the manifold coil placement) would not reach to that location. This was easily solved by unwrapping the tape on the new harness, and folding back the two coil wires to reach the 6-pack coil location.

B.   The green and blue wires for the original field wire connections on the OEM alternator would not be required on the new one wire alternator, so could be terminated and wrapped in the harness or removed completely.  I understand that the field wires were to illuminate the dash warning light.

C.   Missing from the new M&H harness was a wire for a solenoid on the left side of the manifold for the 6-pack carb setup.  My aftermarket (Promax) 6-pack setup does not include the OEM solenoid, so this was not a problem.

So now that I have identified how to make the M&H harness work for my application by repositioning the coil wires, and deleting the field wires. I have the following decisions to make.

1.   I need to run a new wire from the one wire alternator to the battery, or starter relay on the fire wall. I plan on making this connection with a 6-gauge wire from the alternator to the starter relay with the wire wrapped alongside the new wires in the M&H harness. 

2.   Powermaster tech support has informed me that the wire in the new M&H harness that connects the OEM alternator to the regulator on the fire wall is not needed, but that the OEM type regulator has to remain in place as power flows through that component from the starter relay to the interior of the car.  I plan to terminate the wire and wrap it in retaped M&H wiring harness. Can the two wires that plug into the firewall regulator plug (green/blue) just be cut and spiced together so the regulator itself can be removed??? Coincidence in color, or are these the two field wires??

3.   I have temporarily connected the two under dash wires to the ammeter, but still have a decision to make on some additional connection through those joined wires.  My car originally came with power windows, and the lead for that wiring came off a connection to one of the ammeter posts. Additionally, I have upgraded the interior to include heated Corbeau front buckets, so I have another high draw lead to connect somewhere under the dash. One thought is to connect the two original ammeter wires through a new 3 to 4 circuit block with fuses for each of the 3 or 4 circuits. This would provide separate fuse protection for the power windows and heated seats, and leave me at least one additional fused connection for an upgraded stereo system.
Please weigh in and let me know if I have overlooked something, or am incorrect in my plan on the electrical connections.

Regards,
Mike Newell