check your fusible links. I hate them. I rewired my 85 under the hood because the past owner butchered the original harness so badly. Had several of the fusible links blown and poorly cobbled. I went to a junkyard and started with a whole underhood harness from a junker that was in good shape. I then untaped both harnesses, and fixed any bad spots (brittle insulation mostly) in the junkyard sourced harness. Everything I touched, was reattached with crimped bare barrel connectors, soldered and heat shrink wrapped.
I then went back to the junkyard and got an underhood fuse box off of another vehicle, and grafted it into the junkyard sourced harness, I eliminated every fusible link, running those circuits thru the fuse box.
I didn't care about car brand when looking at fuse boxes, looking for something big enough for my needs, but didn't need anything that would take up the whole fenderwell.
I wound up cutting the fuse box and bracket from a 90-92 Ranger. Plenty of fuse slots, with a few for future use consideration, and has the **** fuses. Plenty of area on fuse blades so I don't get heat buildup like you can with smaller fuses due to lack of contact area.
The harness I got came from an 84, comparing 84 and 85 wiring diagrams all the difference I could find was that one of the wiper control wires was in a different spot between them, and the wiper plug was different at the motor. I disengaged the terminals on both the original and the donor harnesses and plugged the terminals into the original plastic plug from the original harness and I had to move 1 wire to a different hole in the bulkhead was it.
I then drew up my own diagram of the fusebox to show what Dodge circuit, that I put to what hole in the fusebox. I judged what wire gauge off the original harness matched up to what gauge wire coming out of the fuse box to determine what amp fuse to run in a given slot. Matched up pretty well/ and fuses are easier to find and replace than fusible link wire out on the road. You will NOT find any info anywhere about rated capacity of fusible link wire, only a standard wire color chart that says "this" color wire is "this" gauge size of wire. Meaningless. Then consider that any circuit that has a fusible link, that link is 3 gauge sizes smaller than the parent circuit. That means a strip of 16 ga wire in an otherwise 10ga circuit.
Then there was my son's 89 Ramcharger. We swapped it back to a carb'd system. The TBI system Dodge used 88-92 sucked. would not have even run the 408 engine he put in. and not reprogrammable either back then. We did the same with his fusible links, as I did with mine but used a different underhood fuse box.
Went with what the junkyard had at the time we were doing the job.
We actually did this retrofit before I did mine. and learned a few things about the differences in Dodge truck wiring setups thru the 80s. Initially the plan was to plug n play with a complete underhood wiring harness from a 1985 to eliminate all the fuel injection wiring. and this next part, may be of particular interest to you! Dodge changed the terminals at the bulkhead (the pass thru connector at the firewall) some time late in the 1985 model run. The early 85s were a wide blade connector, like the earlier 80s trucks. In the later 85 trucks they changed to a skinnier blade terminal at the bulkhead. In my opinion the older wider blade terminals are better/ as the more contact area you have at any kind of terminals, the better it will resist corrosion and heat, will be less resistance in the circuit. so if your 85 is a late model it should plug right into the 87 cab half of the bulkhead.
Lastly I just bought a 2012. Been looking for quite a while as long bed regular cab trucks are tough to find in a more modern truck. the more I look into this thing the more I appreciate my 85. The 12 has lots of things that weren't thought of in 85, that can strand you. The 85 is simpler, and anything that don't exist cannot leave you on the side of teh road!!!!
probably more info than you wanted but you can tell I have PLENTY of time under the hoods of 80s trucks. At least I can readily fix them, not so much the newer rigs.
