Where Does This Wire Go?

[blahboybaz]

I've had a couple engine fires in that truck and the wiring had gotten pretty messed up. I replaced each damaged wire with matching color but there is one wire I can not figure out what it is. I realize that it's possible not to be stock (wiring can be altered) but then again maybe it is. I need to find out what the wire is for and what it connects to at both ends. I've included an annotated picture that says it all but the copy at the link below might be clearer to see that words. If there are any old school mopar guys around that might just recognize what it is by looking at it I would really appreciate the help.

PS: If the pic above isn't clear enough here is a link to one that is.. 'clearer picture on imgur'

 

[Mr.Mopower]

Wiring – MyMopar

 

[blahboybaz]

Ty. I've been looking in that but to be honest I really don't understand how to read a wiring diagram and I'm not seeing anything that looks like what I'm trying to identify. I don't see any indication of the firewall in any of the diagrams which makes it challenging to see if a wire passes through the firewall to try and match it up. The few diagrams I think might contain what I'm looking for seem to be broken up into sections covering several individual pages (so not knowing how to match things up / read a diagram like that I'm having trouble finding the corresponding thing on the next page / part of the diagram. And; while a information for a different year vehicle may often be applicable it might not as well - sometimes they make pretty sweeping changes to a system in the vehicle and it is no longer applicable to the different year - the manufacturer decided to stop at 1978 for information for the previous year(s) and to make a specific set of information for 1979.

I'm sorry - I'm in over my head in terms of getting the information I need to solve this problem. I can connect a wire to something I know how to do that but there's a lot I don't know in order to find the answer.

Is there someone who just knows what things are under the hood (or how to read an electrical diagram and vett whether the info is relevant for a 1978 W200)?

 

[Mr.Mopower]

These are what I buy. I get the big one.
Easiest way to learn where that red wire goes is either crawl under the dash to see where it starts and what its hooked to. Or test for power using a multimeter and pop the fuses out one at a time to see if one kills the power at the end.
If you don't know how to use a multimeter. Youtube is your friend
Here's your fuse box.
Black wire is probably a ground. You can check that with a multimeter also.





1978 Dodge D & W Series Truck Color Wiring Diagram

 

[58pwrwgn]

78 is a bit new for me. But dodge ran wires thru the bulk head connector. I assume the wire don't connect to any thing in the engine or come close to an electrical component. Does the truck run an operate fine now.
Does the red wire look like it was add to the fuse box. My I initial thought is the wire was used to power the cab due to other dash/bulk head wire issues or to power something in the engine compartment.
What does the black wire go to inside the cab.

 

[blahboybaz]

These are what I buy. I get the big one.
Easiest way to learn where that red wire goes is either crawl under the dash to see where it starts and what its hooked to. Or test for power using a multimeter and pop the fuses out one at a time to see if one kills the power at the end.
If you don't know how to use a multimeter. Youtube is your friend
Here's your fuse box.
Black wire is probably a ground. You can check that with a multimeter also.





1978 Dodge D & W Series Truck Color Wiring Diagram

View attachment 24924

Thank you. I guess I'm going to have to learn to use a multimeter and to troubleshoot. I've been dreading the though of it.

 

[blahboybaz]

78 is a bit new for me. But dodge ran wires thru the bulk head connector. I assume the wire don't connect to any thing in the engine or come close to an electrical component. Does the truck run an operate fine now.
Does the red wire look like it was add to the fuse box. My I initial thought is the wire was used to power the cab due to other dash/bulk head wire issues or to power something in the engine compartment.
What does the black wire go to inside the cab.

It did run. It ran like a raped ape! Then I began some much needed exhaust work - which became much more extensive than I though - the whole top end got tore down. She's got a bunch of new parts now (head gaskets, valley pan, plugs, wires, carb, etc, etc). I should be the point to start the truck, dial in the carb, and be on the road again but I have no spark. That wire may or may not have something to do with that but the only way to find out is to find out about the wire so it puts me right back at that.

Not sure where the black wire goes I don't think I thought to check it out. I should try to check that out and get my endoscope out again see if I can see something more.