Wiring diagram Bulk Head Confusion

[tparker]

I have the 1970 Challenger Service Manual (reprint) and am confused. I was about ready to do the Alternator and ammeter upgrade and started looking at the bulkhead connectors. I needed to trace them out anyways just to make sure I knew where everything was supposed to be.

I spent a couple hours tracing based on the wiring diagram labeled 'Engine Compartment Wiring Diagram-Except Hemi-Engines-Challenger-Dart'. It turns out this doesn't match my car, and I am not event sure what the title is saying. Is it excluding Hemi Engines for Hemi and Darts? But it is worded odd. Then there is another diagram labeled 'Engine Compartment Wiring Diagram-Hemi-Engines-Challenger'. This diagram matches my car much more closely with the exception of Air conditioning and air blower. The Diagram for the challenger shows 3 connectors, the Hemi Challenger diagram has 4 connectors (2 large and two small), which is the same as mine.

My car is a 1970 Challenger Western Sport Special with a 318 originally. Why would it follow the Hemi Electrical setup? Is this common? I suppose some one could have swapped it, but that doesn't make any sense.

[71383bee]

That's interesting.  I pulled out my 70 FSM and looked under the hoods of both my 70 and 73. 

I agree that the non-hemi diagram is confusing and the "hemi" diagram is more accurate.  The "hemi" diagram also references a second inline bulkhead that would run on the right hand corner of the engine that would include the black alternator feed.  My 70  harness does not have this.  My 73 does. 

I attached pictures of my believed to be stock 70 wiring and my recently reproduction 73 harness and they are very similar. 

For the bypass you are mainly concerned with the 12 ga black alternator feed wire that goes to post 18 and the 10 ga red battery feed wire that goes to post 16.  if you will see these go to separate harnesses.  For the bypass i typically do not touch the stock current feeds and run a solid 10 ga wire along the looms from the alternator discharge post to a 14 ga fusible link that ties directly to the positive bat post on the relay.  This results in an incorrect reading of the ammeter gauge but is a direct feed from the alt to the bat the bypasses the ammeter connection.  You can also replicate the ammeter function if you do a parallel bypass which goes into the dash but that involves either modifying the harnesses or drilling more holes into the firewall to feed the feed wires in. 

I hope this clears things up a bit. 

[tparker]

Cool. At least I'm not crazy or have some wacky setup. LOL. Yeah, I don't have that second connector either. Thanks for chiming in.

[Indiana Challenger Guy]

I am new to the forum, but I am having similar issues that tparker mentioned. I have a 70 Challenger RT that I have owned for several years and I am finally at a point in life where I'm able to start restoring it. When I look at the service manual on the wiring schematic I am confused (color schematic attached). The service manual identifies plug J-R as the center plug in the bulkhead. On my harness, everything that is identified on the J-R plug is actually located on the S-Z plug on the bulkhead. When I looked at your photo of your 70 challenger, it appears to be similar or the same, I just can't identify all the wires on the plug.

I have attached a photo of my wiring in the plug. It is wired as follows from top to bottom, left to right looking at the rear of the plug:
Grey- oil pressure gauge sending unit (G6-18GY)
Violet- temperature gauge sending unit (G2-18V)
Black- alternator/battery (R6-12BK)
Brown- ignition ballast resistor (J3-14BR)
Brown- windshield washer motor (V10-18BR)
Blue w/white tracer- splice for alternator/voltage regulator/ignition ballast (J2-16DBL*)
Grey w/black tracer- tachometer (negative side of coil) (T11-18GY*)
Dark Green w/red tracer- horn (H2-16DGN*)

This seems to match what I have at the bulkhead coming from the rally dash. My confusion is that even if I place the wires on the S-Z plug location on the bulkhead, which is what appears to be on your car, they are still in a different order than what the service manual schematic shows. I was curious if this wiring order is the same as what you have on your 70. (I added the tach wire). Also when I look at the schematic I have no idea what the A1B-16DBL with fusible link is or where it would go.

Any advice or help you could offer would be greatly appreciated. I think I'm going crazy 😜.

[71383bee]

I am new to the forum, but I am having similar issues that tparker mentioned. I have a 70 Challenger RT that I have owned for several years and I am finally at a point in life where I'm able to start restoring it. When I look at the service manual on the wiring schematic I am confused (color somatic attached). The service manual identifies plug J-R as the center plug in the bulkhead. On my harness, everything that is identified on the J-R plug is actually located on the S-Z plug on the bulkhead. When I looked at your photo of your 70 challenger, it appears to be similar or the same, I just can't identify all the wires on the plug.

I have attached a photo of my wiring in the plug. It is wired as follows from top to bottom, left to right looking at the rear of the plug:
Grey- oil pressure gauge sending unit (G6-18GY) POST 17
Violet- temperature gauge sending unit (G2-18V) POST 21
Black- alternator/battery (R6-12BK) POST 18
Brown- ignition ballast resistor (J3-14BR) POST 22
Brown- windshield washer motor (V10-18BR) POST 19
Blue w/white tracer- splice for alternator/voltage regulator/ignition ballast (J2-16DBL*) POST 23
Grey w/black tracer- tachometer (negative side of coil) (T11-18GY*) POST 20
Dark Green w/red tracer- horn (H2-16DGN*) POST 24

This seems to match what I have at the bulkhead coming from the rally dash. My confusion is that even if I place the wires on the S-Z plug location on the bulkhead, which is what appears to be on your car, they are still in a different order than what the service manual schematic shows. I was curious if this wiring order is the same as what you have on your 70. (I added the tach wire). Also when I look at the schematic I have no idea what the A1B-16DBL with fusible link is or where it would go.

Any advice or help you could offer would be greatly appreciated. I think I'm going crazy 😜.

Welcome to the site!

I believe there was a mislabeling of the 70 wiring schematic back in the day.  The bulkhead connections for 70 on up cars are shared with the B body platform rather than the A body platform and therefore are more accurately depicted on the following page in the FSM as page 8-90 Fig 5 Engine Compartment Wiring for HEMI engines -  Challenger.  The bulkhead layout is the same style used on later years as well.  The wiring harness you have pictures is commonly called the "Engine Forward Harness"  which contains all of the wiring on the right side of the engine bay to feed the ignition system, sensors, carb power, alternator, voltage reg, horns and window wash.  It lays along the right cylinder head. 

I also have a 73 and sometimes use that schematic more often than the 70.  The wiring is very close with some minor tweaks.  Either way flip to the next page an you should be good. 

[Indiana Challenger Guy]

Thanks for the quick response. I will pull up the B body engine harness schematic and check against it. I was starting to think I was crazy. I'm not the smartest man in the world but I thought I could read a basic wiring schematic. 

[Indiana Challenger Guy]

I just checked my Engine Forward Harness against the hemi engine schematic, and it is identical. I can't thank you enough for the advice. I have been pulling my hair out and I don't have any😂.

The previous owner(s) butchered the wiring harnesses in the dash and the engine compartment. My biggest fear is a big puff of smoke when the battery was connected. As you know, that's like letting the genie out of the bottle. Once the smoke comes out, you can never get the genie back in it.

I feel relieved and can't thank you enough for the advice.

[71383bee]

I'm glad to hear it worked out! 

Wiring can be very intimidating but when you break it to basics it is very logical.

I too was stumped by the 70 FSM but having the experience on my 73 and my 71/72 b bodies helped me.

Let me know if you run into more issues.


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[70 Top Banana]

I have a car with some of the same issues. Whoever hacked the wiring in that car should never have been allowed to open a hood!    What they did and why is a complete mystery to me. I fixed some of egregious work but I am thinking I might buy the engine forward harness and replace it.

[71383bee]

On all all of the cars I've owned I tend to replace all of the forward harnesses within the first few months along with the battery cables unless it is obvious they are new.

It's just good insurance and it clears up a lot of headaches. Considering the cost is around 300 or do to do them it's money well spent.


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[70 Top Banana]

Yes, I agree. The one thing I don't do is leave the car connected to the  battery. With the work I have done, it is ok to drive and I have chase a lot of wires in the car but you are right. I will get a new engine harness and the battery cables. Thanks!

[70 Top Banana]

Thanks for the pictures. I am having some of the same problems. The owner should have never been allowed to own a pair of wire cutters/strippers!