85 GL1200 loses fires when fan comes on


Information and questions on GL1200 Goldwings (1984-1987)
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Pineaus
Posts: 1
Joined: Tue Sep 30, 2014 9:45 am
Location: Canada
Motorcycle: 1985 GL1200 Aspencade
2003 GL1800

85 GL1200 loses fires when fan comes on

Postby Pineaus » Tue Sep 30, 2014 9:53 am



We have a 1985 GL1200 Aspencade, it loses fire in the 1-3 coil when the radiator fan comes on. Replaced the affected coil but the problem continues. Let it cool down it starts back up and runs till the fan comes on again. no fire in the 1-3 coil but has fire in the 2-4 coil.



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virgilmobile
Posts: 7659
Joined: Sun Sep 19, 2010 5:39 pm
Location: Denham Springs,La.
Motorcycle: 1988 GL1500 I
Previously owned
78 GL1000
81 GL1100
82 GL1100 I
83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: 85 GL1200 loses fires when fan comes onq

Postby virgilmobile » Tue Sep 30, 2014 11:42 am

Cool...a strange problem...
Both coils have common power ...should that power dip below,say 10 volts or so,one coil could quit leaving the second coil with enough to run.
Now when the fan kicks on (its powered from the same wiring) there is current draw and some voltage drop.One coil,which is electronicly controlled,dies.
With your volt meter,monitor the power wire feeding both coils..I think its black...
When the fan kicks on,see if the voltage drops below 11.5 volts.
The ECM,if I remember correctly also has a black power wire.it too must stay above 11.5 volts to keep it sparking.
If you do have a significant voltage loss(drop) ,you can suspect a dirty kill switch,corroded grounds,charging issues.bad grounds at the regulator.
Also read the battery voltage with the bike at 3000 rpm.Expect it to be above 13.8 volts and stay up there even with the fan running.
It is also possible the fan is drawing an excessive ammount of power.If its binding or turning slow the current goes way up.
I'm not certain the current needed but I don't think it draws more than 8 amp or so.
If the battery stays up ok but the volts at the coils drop,you could for testing only,run a #10 wire from the battery direct to the coils to see if it stays running with the fan on.
This would eliminate any problems in the ignition system and point to the fan or wiring being the problem.
Keep us posted on what you find.

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Charlie1Horse
Posts: 165
Joined: Mon Sep 16, 2013 9:35 pm
Location: Jacksonville, Florida
Motorcycle: 1986 GL1200A Aspencade 4Sale soon
1992 GL1500I Interstate

Re: 85 GL1200 loses fires when fan comes on

Postby Charlie1Horse » Wed Oct 01, 2014 11:40 pm

After being an auto mechanic for many years if one device shuts down when another powers up I find it is usually a bad ground. Check all your ground wires and connectors. Clean any corrosion on the connectors and be sure that the grounds are secure. I always use a little dielectric grease in all plug in connectors as well. Hope this helps.
Charlie1Horse

User avatar
virgilmobile
Posts: 7659
Joined: Sun Sep 19, 2010 5:39 pm
Location: Denham Springs,La.
Motorcycle: 1988 GL1500 I
Previously owned
78 GL1000
81 GL1100
82 GL1100 I
83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: 85 GL1200 loses fires when fan comes on

Postby virgilmobile » Thu Oct 02, 2014 7:09 am

I too find this to be common.
However on the 1200..both coils not only have common power,they have a common ground..the ECM,and it has just one ground wire.
Current will take the easiest path to ground.This just happens to be through one coil and half of the ECM.
At least in my mind.
Another thought.if the voltage to the ECM is dropping AND there is just a bit of corrosion in the 4 wire pulse coil plug(next to the battery),this could kill half the ignition.
My 84 failed to spark once.intermittently.that plug has a very small voltage on it.Any inturruption can kill one spark.
The plug was corroded just like the regulator and stator plugs.




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