MCI 102-C3 coach to RV - Electrical System

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    MCI 102-C3 coach to RV - Electrical System

    This thread is the electrical system offshoot of the original thread that migrated from Pirate4x4. As the subtitle implies, all things related to the electrical system will be here. The mother thread, which begins as the bus purchase and teardown, lies here - https://irate4x4.com/tow-rigs-and-tr...eral-floorplan

    The second post of this thread starts off where I was knee-deep in stripping the bus floor out and getting my hands extra dirty in the engine bay. The rear electrical junction box also resided here, therefore was the next victim. Everything from the first round of OE electrical removal to buttoning up and testing the final system will be here.
    Last edited by JNHEscher; 09-30-2020, 06:46 PM.

    #2
    Our progress was delayed by a couple days when low temps and high winds arrived. Today was better, so we headed to the bus. Got a number of tasks completed.

    The rear electrical box is held up by only four bolts. Quite easy to take loose and set aside. The very last of the flooring sheet metal was sandwiched between the box and floor framework.

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      #3
      Today, I pulled out all of the pneumatic apparatus that controlled the belt tensioner air cylinder and the radiator louver air cylinders. If I keep the louvers, they'll be as reconnecting the feed line to an air source. The thermostatic valve may be faulty, being the reason the louvers weren't working before. I'll have to open it up give it a few pokes. I put a cap over the air feed that dispersed to everything I pulled out today so the rest to the system still functions.

      The next task was pulling and labeling all of the wiring leading to the AC and headlight relay junction box that was in the first storage bay. Unused wiring and components will get ditched and what's left that will be needed will get run in conduit that is going to go in the center chase. All wiring, air lines, and plumbing will be installed through conduits in the chase to allow ease of installation, testing, removal, and future additions. The whole bus will be rewired, but I'm keeping necessary systems connected for the time being so that I may trace them all.

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        #4
        Spent all of today tracing and pulling air lines that operated all accessories. Bay door locks, entry door, entry door latch, curb step, curb step lock, wipers, and washer fluid. All of those ran through their respective control valves and then converged at a steel manifold under the floor. That manifold also has a couple copper lines on it, along with the 3/8" line coming from the emergency bay door tank. I disconnected every line from the manifold and will be picking up a tee flare tomorrow to reconnect the two copper lines with the line from the emergency fill.

        Ended the day rerouting the main positive cable between the bay junction box and the driver junction box. Began pulling circuits that won't be needed. The vast majority of it is passenger lighting that already got cut during the initial interior teardown.

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          #5
          GLTHFJ60 said,

          God damn that's a lot of wiring.

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            #6
            Java said,

            Awesome progress! All those wiring pictures give me the shivers..... So much squirrel nest of unlabeled wires..... UGH.

            Why are you doing away with all the air accessories? I can see the door, but bay locks seem handy.

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              #7
              More wiring. Continued to separate wiring from the rear junction box. It's a hell of a job. Got around half way through this portion of it today. These junction boxes serve more as electrical testing points than actual junction boxes. Most of the wires passing through appear to be connected at the studs only to provide diagnostics points. Cool, but shit balls is it a rat's nest.

              There have been five or six redundant wires in each box. I pulled all of those first to make room. The wire loom running from front to rear was packed pretty tightly. Whenever I start rebuilding the wiring harness, I'll be sourcing all of the wire colors that match the printed color names on each wire if possible. At least half of the wires will disappear since it goes to systems that have been removed. The engine and trans don't use much. In fact, I'd say about a third of the engine wires will get pulled out. There's a few duplicate grounds.

              Got final measurements for the power steering and air lines and ordered a pile of DOT air brake line tonight. The copper hard lines in the center chase are quite nice, but make for a hell of a time accessing stuff beyond them within the chase. Because of where they're located, you either have to bend them in short sections to get them around the engine or pull the engine altogether to slide the pipes out.

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                #8
                MarkObtinaro said,

                I had several thoughts as I have been reading about your deconstruction.

                Since you have so much of the dash board taken apart it would be a GREAT time to swap the air wiper motors for electric motors. Luke @ US Coach has some very affordable retrofit units that are not very expensive.

                I understand taking out the coach A/C but I have to wonder if you are going to be putting back in the front heater/defroster core. It will be very difficult to heat or defrost the front of the bus without some sort of heater/defroster.

                The alternator may only be 270 AMPS but it is a 24-volt alternator. That is about the same amount of juice as a 500 AMPS 12-volt alternator. It was designed to be able to operate the coach A/C system at idle without draining the batteries. The condenser fan(s) alone took about 50 AMPS.

                Make sure as you are taking out wiring that you keep the 12-vdc and 24-vdc wiring clearly marked. Your coach may not have any 12-vdc but if you do and you put 24-vdc into it you will have smoke escaping from your wiring. Also, if you only put 12-vdc into the 24-vdc side of things you won't have stuff working.

                It might be a good time to swap out all of the 24-vdc lights and any remaining blower fans with 12-vdc versions. The cost of 24-vdc anything is considerably more expensive than 12-vdc versions of the same thing. It is much easier and less expensive to find 12-vdc LED's or upgraded headlights than it is to find 24-vdc LED's or upgraded headlights.

                With everything torn apart it would be fairly simple to step down the voltage at the alternator or swap out the 24-vdc alternator with a 12-vdc version. About the only thing that really needs 24-vdc would be the starter and there are newer 12-vdc alternatives that will spin faster and won't weigh 65 lbs.

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                  #9
                  [486] said,
                  MarkObtinaro said:
                  The cost of 24-vdc anything is considerably more expensive than 12-vdc versions of the same thing. It is much easier and less expensive to find 12-vdc LED's or upgraded headlights than it is to find 24-vdc LED's or upgraded headlights.
                  Just an excuse to run two of everything, in series so that they're each seeing 12v.

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                    #10
                    Braved the sand storms alone to finish up the rear j-box. At least a third of the wires were dead ends, meant for options we don't have like the jake brake. I'm sure some are there to be used to complete a circuit that failed because of a broken wire. Some wires were taped, others were crimped with ring terminals and anchored to studs alone. Tomorrow I get to yank each wire out of the chase and reconnect the ones still necessary.

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                      #11
                      MarkObtinaro said:
                      I had several thoughts as I have been reading about your deconstruction.

                      Since you have so much of the dash board taken apart it would be a GREAT time to swap the air wiper motors for electric motors. Luke @ US Coach has some very affordable retrofit units that are not very expensive.

                      I understand taking out the coach A/C but I have to wonder if you are going to be putting back in the front heater/defroster core. It will be very difficult to heat or defrost the front of the bus without some sort of heater/defroster.

                      The alternator may only be 270 AMPS but it is a 24-volt alternator. That is about the same amount of juice as a 500 AMPS 12-volt alternator. It was designed to be able to operate the coach A/C system at idle without draining the batteries. The condenser fan(s) alone took about 50 AMPS.

                      Make sure as you are taking out wiring that you keep the 12-vdc and 24-vdc wiring clearly marked. Your coach may not have any 12-vdc but if you do and you put 24-vdc into it you will have smoke escaping from your wiring. Also, if you only put 12-vdc into the 24-vdc side of things you won't have stuff working.

                      It might be a good time to swap out all of the 24-vdc lights and any remaining blower fans with 12-vdc versions. The cost of 24-vdc anything is considerably more expensive than 12-vdc versions of the same thing. It is much easier and less expensive to find 12-vdc LED's or upgraded headlights than it is to find 24-vdc LED's or upgraded headlights.

                      With everything torn apart it would be fairly simple to step down the voltage at the alternator or swap out the 24-vdc alternator with a 12-vdc version. About the only thing that really needs 24-vdc would be the starter and there are newer 12-vdc alternatives that will spin faster and won't weigh 65 lbs.
                      Click to expand...
                      Didn't see this until just now. Everything but the wipers and what voltage we're going with is taken care of. I knew there were electric wiper motors that fit in, but hadn't looked into what they cost yet. They're likely what we'll use. 12 or 24, still contemplating this.

                      Because many of the components on the bus that I can't produce myself are already 24 volt, sticking with said voltage would be easy. The lighting voltage I don't care about. Super easy to wire accordingly. Solar charge controllers do better at 24. DC to AC inverter uses less amperage at 24. I've already nailed down 24-volt replacement parts for cheap that I can swap into whatever appliance I need.

                      Going with the common 12 volts, almost anything can be had anywhere. Wouldn't have to buy batteries in pairs for the solar battery bank (two 12's). I thought that we might set up the solar and engine systems to be separate. I'm still steadily weighing the pros and cons of 12 and 24 volts. With 24 volts, I can charge my cordless tools without stepping up the voltage.

                      Watts is watts, so it's a trade-off for either choice. As I peel through the rest of the OE wiring, I'll see how much of it really needs 12 volts.

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                        #12
                        Today was spent pulling the wires from the center. Got all wires between the engine bay and driver's j-box pulled through and reconnected. Had the wife helping. While she was cutting tape from the windshield pillar harness, she pointed out that some of the wires looked burnt. Then we spotted where somebody had ran a screw through them.

                        We had started off by pulling all the unused wires. From what I could determine by the door legend, they were all for the jake brake and DDEC. There's going to be several wires for the AC that I need to take out. Engine and trans harness should get pretty slim.

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                          #13
                          Pulling the wires all the way through required pulling them through the center and out this bend in the spare tire compartment, then pulling from there to the driver's j-box. Couldn't get 45-foot wires to pull around that bend until about two thirds of them were out.

                          All wires have been laid up on the floor and reconnected. I have a few more to pull tomorrow. Between the storage bay j-box and driver's j-box. Then a couple from a regulator to the engine bay. Should be picking up conduits on Tuesday, if all goes well. Started planning where to route the conduit for the wiring. We have some weatherproof boxes on the way. FedEx is being incredibly slow with them.

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                            #14
                            BIG-O said,

                            What in the world do all those wires do?

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                              #15
                              BIG-O said:
                              What in the world do all those wires do?
                              A few various engine controls, a couple transmission do-dads, a crap load of lights and a some blower fans. A lot of it is for stuff that isn't on our bus. I'll have this thing down to maybe a dozen wires by the time I'm done.

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