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PostPosted: Sat Oct 14, 2017 11:06 pm 
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On the main road

Joined: Tue Aug 02, 2011 8:25 pm
Posts: 182
Country: New Zealand
Bikes owned: 72 T500J, 72 Kaw H1-B, 71 CB750 K1, 67 A7SS
I have a small problem which I cannot seem to find the cause. I fitted the battery in my 75 GT550 a week ago after a full restoration. The turn signal relay is the original Nippon Denso (JFK-0080, 23w x 2 x 1.7w. 12.8v) and everything on the bike electrically works fine apart from a problem with the LH side turn signals;

Ignition on and engine run switch OFF, both RH turn signals flash on/off and as well as the indicator light, however when you switch to the LH side, only the front LH signal comes on as well as the indicator light, however there is no flashing at all.

Alternatively:

Ignition on and engine run switch ON, both RH turn signals and indicator light come on but do not flash at all. When you switch to the LH side again the LH signal comes on as well as the indicator light - there is no flashing.

I have checked all of the wiring hardness connectors with my meter and all of the colour connectors match up. I also checked all the bulbs, earth leads and turn signal earth points and everything is in order. I then found an old signal relay from a 72 Suz T500 which seemed to be exactly the same relay as the GT550. I wired this up and got the following results:

Ignition switch on and engine run switch in either the ON and/or OFF position, both RH turn signals flash on/off and as well as the indicator light, however when you switch to the LH side, again only the front LH signal comes on as well as the indicator light - there is no flashing.

Could the signal relay be causing this problem? Maybe both the GT550 and old T500 replays are faulty. Any ideas on how to fix this problem would greatly be appreciated.


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PostPosted: Sun Oct 15, 2017 2:45 am 
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Moto GP
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Joined: Mon Dec 13, 2010 4:32 pm
Posts: 3242
Location: southwestern Pennsylvania
Country: USA
Bikes owned: 69 T350 thru 75 GT750
The stock flasher needs the current from two bulbs for it to flash properly. Its designed to stay on and NOT flash if there isn’t enough current.

So the right side flashes properly when the engine run switch is OFF.
With the engine run switch ON & the engine NOT running, the voltage drops a bit more. So the current drops a bit more too.
That current drop was enough for the original GT550 flasher to stop flashing.
You should check the battery voltage to see how low it went. If it was close to 12V, then its a good idea to replace the original GT550 flasher.
If the voltage was low, then maybe you just need to charge or replace the battery.

The left side has a different issue.
Since only one bulb works, the turn signal will NOT flash — this is a design feature of these flashers.
Swap the rear turn signals. If the left side then works correctly & the right doesn’t, then you have a bad turn signal.

_________________
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 project & 75
GT380 72
T500 73 project
T350 69, 71 & 72 project
T250 72
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE


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PostPosted: Sun Oct 15, 2017 12:47 pm 
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On the main road

Joined: Tue Aug 02, 2011 8:25 pm
Posts: 182
Country: New Zealand
Bikes owned: 72 T500J, 72 Kaw H1-B, 71 CB750 K1, 67 A7SS
Hello Jabch - Thanks for your comments which is much appreciated

I fitted a set of new GT550 turn signals which came from Diablo Cycle - see below. A friend also mentioned that I should also check the earthing of the handlebar which is a good point as both the handlebar clamps and steering head were repainted and the clamps are rubber mounted. Should there be an earth strap for the handlebar? Would the earth point come from the metal to metal contact from the two sides of alum control switch housings?

www.diablocycle.com/Suzuki-GT750-GT550- ... ignal.html
www.diablocycle.com/Suzuki-GT750-GT550- ... ignal.html

The battery is a new Motobatt MB10U gel battery, however I'll check the voltage as suggested.

The really strange thing is that when I swapped over the GT550 turn signal relay with the T500 relay, with the ignition switch on and engine run switch in either the ON and/or OFF position, both RH turn signals flash on/off and as well as the indicator light.


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PostPosted: Sun Oct 15, 2017 12:55 pm 
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Novice racer
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Joined: Wed Jan 18, 2012 8:01 pm
Posts: 930
Location: North of Albany, NY
Country: USA
Bikes owned: T500R (now), T500M (30 yrs ago)
Syd wrote:
I fitted a set of new GT550 turn signals which came from Diablo Cycle - see below.


Check that the bulbs fitted in these after market turn signals are the same model as specified by Suzuki. Different bulb == different current draw. And as jabcb correctly stated earlier, the old mechanical turn signal relay is *very* dependent on a particular current flow.


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PostPosted: Sun Oct 15, 2017 1:16 pm 
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On the main road

Joined: Tue Aug 02, 2011 8:25 pm
Posts: 182
Country: New Zealand
Bikes owned: 72 T500J, 72 Kaw H1-B, 71 CB750 K1, 67 A7SS
Thanks, I'll check out the original bulbs and compare these to the new bulbs which are 23w. Do you think the handlebar earth could be a factor?


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