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79 GS1000E Turn Signal Issue

  • Thread starter Thread starter Pipefighter
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Pipefighter

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My left side turn signal was working intermittently, now it's not working at all. I've checked the wiring, connectors, relay, turn signal switch, swapped left and right hot leads, (all bulbs OK), and grounds. The only thing I haven't checked is the TSCU. Suzuki utilized the same TSCU, turn signal control unit, in only the 78 & 79 GS850/1000. OEM #38830-49001. Could that be the cause, and does anyone know of a way to trouble shoot it? Thanks.
 
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The tscu is probably shot. Not many of them seem to last 40 years. Best bet is to install a manual switch. I built a gadget with automotive relays that controls the turn signals with the stock switch just to see if I could. I could dig up my schematic if you'd like but it's probably easier to change the switch. You may find a working tscu if you're lucky.
 
You could start with cleaning all the bulb sockets and connections and applying dielectric grease. It helped mine for a little while but eventually it will be total failure. I ended up removing the module, disabled the distance counter switch in the speedometer, wired in two blinker relays one for each side and got so used to holding the switch on manually that I never did anything else. The cancel switch is disabled, the turn signals go off as soon as you release the switch and you never leave the turn signals on by mistake. That would be the easiest way to go and it is fool proof.
 
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Bad TSCU seems to be the case. I'm wondering if anyone has figured out how to make the newer TSCU work in the older GS's. Lots of those for sale on eBay.
 
I have the same issue only on the right side. When turning on the left side I can hear the signal through the unit that sits by the battery on the left side of the bike. When trying to switch on the right signal, no click at the little thingy by the battery. Is that the TSCU unit? and if so, what is the larger rectangular unit on the other side of the battery?

In my situation, I am getting ready to remove and clean the switch as an earlier thread suggested the switch might be the culprit.
 
The large, two plug unit directly attached to the battery box IS the TSCU. The smaller one, next to the starter solenoid and fuse box is the turn signal relay. Sounds like you probably have a bad tscu like I do.
 
Solved! For now. The schematic shows the horns tied in to this system, so I pulled fuel tank, disconnected and reconnected all horn connections, honked a couple of times and now turn signals are back working! You might want to give that a try and see if it helps. Today I was pricing a new TSCU. Ranged from $326.00 to a high of almost $700.00! Turns out, they are on nationwide back order from Japan. No one has any in stock and there's no telling when they'll be available again. That being said, looks like I dodged a major bullet today. My almost 40 year old TSCU lives!
 
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I think my problem is in the TSCU also. I have it taken apart and when I switch the left side on, the TSCU is operational. When I try the right side, the lights will come on but not flash.
The only thing I have done was to put a test light on top of the little coil looking thing inside the TSCU. On the left side my test light flashes and on the right side the test light comes on but will not go out or flash.

Any suggestions? I don't know of any other testing I could do as I am just guessing the TSCU has given up the ghost.
 
alke46 said:
I think my problem is in the TSCU also. I have it taken apart and when I switch the left side on, the TSCU is operational. When I try the right side, the lights will come on but not flash.
The only thing I have done was to put a test light on top of the little coil looking thing inside the TSCU. On the left side my test light flashes and on the right side the test light comes on but will not go out or flash.

Any suggestions? I don't know of any other testing I could do as I am just guessing the TSCU has given up the ghost.
Click to expand...

I had a similar problem but sometimes, when it was cold out, both signals would work. I decided it was probably the semiconductors in the unit because of that. Definitely something I couldn't fix.
 
When I opened mine up it looked to be in really good shape but I see there is a printed circuit board in there and that's when I just walked away.
 
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