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    #1

    Turn Signal Control Unit :-(

    All,

    I'm having serious electrical problems with my 79 GS850. I think the root cause is that the TSCU is fried. For simplicity I've listed my questions below...

    - Is there a way to test this device?
    - Can the bike/blinkers still function without it?
    - Can it be bypassed?
    - If all above questions are "no", where can I find one? Suzuki wants $320.00; my wife will make me sleep on the bike if I spend that much.


    - Related 'blinker' question: Suzuki wants $41.00 for the turn signal relay. I've been told a standard, two-pronged, automotive turn signal relay will work. Will it? I'd say the TSCU will have to be addressed first.

    Based on schematics provided by the Haynes manual, many things lead to this device. I also am missing oil, neutral, gear, and fuel indicator lights/guage. According to the schematic, these indicators get power from one source/wire: O/G (Green on Orange). I'm still troubleshooting this and will hopefully make progress.

    Please help in any way you can. This old bike has a lot of life left in it and would like to start riding it!!

    Thanks in advance, Jon
    Tags: None
    #2
    Re: Turn Signal Control Unit :-(

    Originally posted by jhult
    All,

    I'm having serious electrical problems with my 79 GS850. I think the root cause is that the TSCU is fried. For simplicity I've listed my questions below...

    - Is there a way to test this device?
    - Can the bike/blinkers still function without it?
    - Can it be bypassed?
    - If all above questions are "no", where can I find one? Suzuki wants $320.00; my wife will make me sleep on the bike if I spend that much.


    - Related 'blinker' question: Suzuki wants $41.00 for the turn signal relay. I've been told a standard, two-pronged, automotive turn signal relay will work. Will it? I'd say the TSCU will have to be addressed first.

    Based on schematics provided by the Haynes manual, many things lead to this device. I also am missing oil, neutral, gear, and fuel indicator lights/guage. According to the schematic, these indicators get power from one source/wire: O/G (Green on Orange). I'm still troubleshooting this and will hopefully make progress.

    Please help in any way you can. This old bike has a lot of life left in it and would like to start riding it!!

    Thanks in advance, Jon
    You can use a standard 2 prong turn signal relay. I've tried a cheapie thermal type and it worked fine. I replaced my relay with an electronic one so I could use some LED lights as turn signals. Turns out I have to mix LEDs on the front and regular on the back because there isn't enough draw with the LEDs for even the electronic relay.

    Anyway you can disconnect that TSCU as far as I know. I disconnected it from my '82 GS1100GK when I put in the new relay, and my signals work fine. I no longer have the automatic shutoff of turn signals now though.. have to turn them off manually. This isn't a big deal for me.

    Comment

      #3
      78-79 system was one with it's own problems. It can be disconnected. The main modification is to the 4 prong plug. . You need to connect the rt front to the rt rear and the same for the left side. I cut the plug from the control unit and modified it and just pluged it back into the harness.
      An auto flasher willl work fine.
      The other problem is the switch itself, since it does not have a detent you will have to hold the switch on. Another option is to use a different switch assembly with a detent and rewire it to your bike. Another option is to mount and use a toggle switch for the turn signal operation. If you figure out the green wire feed for the gauges I would like to know I have the same problem with mine. Don't need gas gauge, I know what gear im in, it still runs so it must have oil pressure

      Comment

        #4
        Jon,

        I studied the schematics, and it seems that all the parts you mentioned and are not working, are connected to the same fuse, together with the horns and the front and rear brake switches.
        I know this sounds obvious, but have you checked that fuse?

        Comment

          #5
          On Mine the fuse is good, horn & brake lights work

          Comment

            #6
            Now it's the turn signals!

            All,

            Thank you very much for your wisdom and expertise regarding my TSCU. I will try and jumper the four pronged plug to see if that does the trick.

            I found the problem with my cockpit lights etc. Within the harness that feeds most of the indicators and fuel gauge, I found two broke wires. One was the famous 'orange' power wire. It broke at the factory crimp where they had joined one wire to three. The other wire was the B/W (white on black). This broke in same fashion; at the factory crimp. Both are now soldered and I have all instrumentation!!

            Now the only thing left that doesn't work is the turn signals. One bit of info that may help everyone is that the bike has a fairing installed. The yahoo that put it on did not solder a single connection! It is amazing how some people will do a half**s job and call it good. The fairing harness is now soldered and in good shape.

            Question: If any of the turn signal light bulbs and/or running lights are burned out will it effect turn signal operation? Keeping in mind that the TSCU is now disconnected and I have installed an automotive flasher unit. Still not working...

            The turn signals are all I have left to fix to make it road ready! Thanks again folks... I didn't realize I was going to need a "support group" when I bought this bike!

            Comment

              #7
              If you were to pull apart your harness, you would find several more connections within the harness. None were ever soldered; all were crimped.
              Bertrand Russell: 'Men are born ignorant, not stupid. They are made stupid by education.'

              ​

              Comment

                #8
                On my GS1100GL if a bulb is burnt out, the signals don't work. Also, what may be an obvious fix to some, did you trace all your wires? When my signals weren't working (I too had some broken wires at the crimps under the seat) and I got it so that everthing seemed fine, they would only work intermittently. I had to trace every ****ing wire I could find, and finally found that the harness in behind the headlight had a female end that was slightly out of shape. Therefore, the male prong would (occassionally) vibrate out of position, and lose contact. It would go for days without working, and then I would fire the bike up, and all would be well. A little squeeze with pliers (and I do mean little), and I haven't had a problem since. This probably has nothing to do with your problem, but its a potential fix if all else fails.
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                hers: 1982 GS850GL - "Angel" and 1969 Suzuki T250 Scrambler
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                #2 son: 1980 GS1000G
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                Comment

                  #9
                  I have a '79 GS1000EN. If you disconnect the TSCU, the signals won't work at all. The unit is a part of the circuit. Disconnecting it is opening the circuit.
                  Over the years, the 2 times I had signal trouble, it was the TSCU.
                  I've only blown 2 bulbs also. It's been quite a while but I think each time a bulb blew, I would thumb the lever and the effected side would light up(example, left front) and it would just stay lit, along with the light in the dash. The left rear, being the bad bulb, would of course not go on.
                  The last time I replaced the unit, I thought I would try something different.
                  Instead of just strapping it with the rubber strap to the battery bracket, I cut a piece of black foam to size(1'' thick) and put it in between the unit and the bracket. It's only been 2 years so I can't say that my "experiment" has ended any problems. I just think it is less exposed to shock and vibration now. I've had these units apart before and there is wiring inside as thin as the hair on your arm. Anyway, I just thought I would add that in. Good luck with it. If your wiring is good, my past experiences say the unit is bad.
                  And on the seventh day,after resting from all that he had done,God went for a ride on his GS!
                  Upon seeing that it was good, he went out again on his ZX14! But just a little bit faster!

                  Comment

                    #10
                    On the 4 prong plug that you cut off of the TSCU connect the green with the green/black connect black with orange/black. Also the flasher will not work? you need to connect it in series with the orange wire from the turn signal switch. Disconnect the orange wire from the switch, hook up a length of wire (18") to the turn signal switch and hook it up to the orange wire and pull the new wire thru the harness, You will now have two wires in the headlight area, they are to be connected to the flasher. just put the flasher inside the headlight and connect the wires

                    Comment

                      #11
                      TSCU / Electrical problems

                      I've had a '79 GS1000 for a number of years now..the bike was given to me, and back then, everything worked fine, except for the charging circuit.. I finally had the time to repair the charging circuit (replaced the RR & the Stator, and some misc. wiring/rewiring).. When I started the bike up, the turn signals and horn didn't work.. I dismantled the switch, and found some corrosion, which I promptly cleaned up. I also found a broken wire for the high-beam switch. Fixed that, and now the left turn signal and horn work fine, but the right signal won't turn on at all.. My next step is to check the wiring to the TSCU and the TSCU itself.. if I wouldn't have pulled the switch apart though, I would have never noticed the corrosion or the broken wire.. it's a decent place to check, and easy enough to dismantle.

                      Comment

                        #12
                        regarding the relay...

                        I just bought a 2-prong 16 amp auto relay and put in my '82 GS650L for blinkers and auto horn. Works great, cost $17

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