! You found the cause of the problem! I'm so happy because there is a chance we can fix it.
I'm not sure which terminal you're referring to, but I see a bunch that need attention. The first step is to shine up the ones near my nifty arrows. If this would be on a tv or vcr, I would just unsolder the corroded terminals and replace them, but I don't recommend that for car computers unless there is no other choice but to junk it if it doesn't work. I used to purposely install a lot of electrical defects, ("bugs"), for my students to diagnose. One of them was a break in a copper trace on the Engine Computer for a '94 Intrepid. The bug was to simulate a failed voltage regulator. I drilled a hole through the board to run a wire to a switch, so the kids could switch the defect in and out as desired. I found out that some of these boards have more than the common copper traces on both sides. This computer had two additional layers sandwiched in the middle, and I drilled right through the circuit that ran one of the injectors. To avoid that potential problem with your computer, if there isn't enough terminal left to shine up, I would try to find a little remaining tab to solder a new terminal to. If that is not an option, solder a pigtail wire to the board, then run that out and attach it to the wire in the plug.
You're still confusing the function of the relay's terminals. 30 and 87 are the two contacts of the switch. They have nothing to do with 85 and 86. Those two are for the electromagnetic coil that runs the contacts. 30 and 87 are switching 12 volts on and off that goes to the fan motor. 86, (I think) or 85 gets 12 volts applied, and the other one gets grounded, (0 volts), to cause it to create the magnetic field that turns the contacts on. Those two circuits, (30 and 87), and (85 and 86), have nothing to do with the operation of the other one. In this case, one coil terminal and one contact terminal each have 12 volts applied, so for convenience, they are tied together inside the computer. That is simply done to reduce the number of wires going to the computer by one. For comparison, you can say the wipers and the radio both have 12 volts applied, so they could be run on the same wire, but the two systems are not related.
Where I added confusion to the story is when discussing the coil circuit in the relay. It needs 12 volts across it to operate. That means 0 volts on one terminal, (ground), and 12 volts on the other. Both are needed to turn the relay on and either one can be removed to stop it from turning on. Since 12 volts is applied to one coil terminal all the time, it is necessary to remove the ground to turn it off. That is actually how most computer-controlled circuits do the on / off switching. What is missing here is we aren't getting the ground on the coil terminal to turn the relay on, and that, I'm pretty sure, is due to the corroded terminals.
You're also going to have to address the mating terminals in the connectors. Given the extremely excessive amount of corrosion, I suspect it doesn't even pay to try to shine them up, then squeeze them tight to make solid contact. Where I would start is by snipping off the needed plugs from a similar vehicle in a salvage yard, then experiment on those first. There will be a locking wedge of a different color, often red, white, yellow, or blue, that must be pried out, then there will be some means of lifting a plastic finger to allow the terminal to be pulled out. You can use one of those terminals to install in your connector body, then splice the wires, or you can buy the correct terminals from the Chrysler dealer's parts department. GM has huge replacement terminal kits specific to each of their car models. Chrysler has every terminal available by the bag. In either case you just buy the number of terminals you need. They can even pick out the correct terminals for you based on application, without you even supplying an old one for comparison. Using original terminals insures they will clip into the connector body and remain firmly seated. When you have a melted connector body, as in an overheated ignition switch or head light switch, you can cut the melted part out, reinstall it that way, then solder on universal replacement crimp-on terminals and plug them in individually.
The reason I want you to practice on a salvage yard connector first is I also ran into a problem on a '97 Dakota. I made a REALLY big deal that no one was ever allowed to pierce a wire's insulation to take a voltage reading, and when I found someone had done that, they got the privilege of replacing that piece of wire, partly so moisture would not get in and corrode the wire, and partly so that poke mark did not become an illegitimate clue for the next person who was going to diagnose this bug. To replace a wire in one of the connectors for the Engine Computer, the terminal had to be removed so the new wire could be crimped and soldered to it. These connectors caused a whole new degree of frustration when trying to reassemble the terminals into the body. It took me more than a few hours to get one back together. I suspect there was some easier way to do it, but I never figured it out. I don't want you to pull your hair out if you have that same style of plug.
As long as I'm sharing all this wondrous information, Chrysler was real good to my Automotive program. The Intrepid was one of about 50 used to evaluate and fine tune a new assembly line. The Dakota was used by their head of training for all of Wisconsin and the UP for about six months. They didn't want either of those released to the public because they had been poked and prodded on so much. Instead, they donated them to one of three college programs they used for their remote training centers. Later, they even built an '03 Durango specifically destined for my program. We received it with less than three miles on it. Thank you, Chrysler.
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Thursday, February 9th, 2017 AT 5:07 PM
