Only getting 6 volts to my tail light


Information and questions on GL1000 Goldwings (1975-1979)
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P8thegr8
Posts: 5
Joined: Tue Mar 29, 2016 9:07 pm
Location: Mason city, ia
Motorcycle: 1978 gl1000

Only getting 6 volts to my tail light

Postby P8thegr8 » Tue Mar 29, 2016 11:13 pm



So just picked up a 78 gl1000. Been riding it a few days now. Just tried to ride for the first time at night and noticed i have no taillight. Of course first thing i did was change the bulb. Brake light works fine still no tail light. So i get my meter. I read 11 volts for the brakelight leadwith lever depressed ,and 0 from the tail light. Take the seat off and have 6 volts on the brown wire leading to tail light jumps to 11 when i turn the key to P. Help



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Bluewaterhooker0
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Location: Tampa, Fl
Motorcycle: 1997 Goldwing GL 1500 SE

Re: Only getting 6 volts to my tail light

Postby Bluewaterhooker0 » Wed Mar 30, 2016 5:10 pm

Not familiar with the 1000, but sounds like either a relay making a poor connection, or the ignition switch, since you can change the ignition switch position and gain the tail light circuit.

P8thegr8
Posts: 5
Joined: Tue Mar 29, 2016 9:07 pm
Location: Mason city, ia
Motorcycle: 1978 gl1000

Re: Only getting 6 volts to my tail light

Postby P8thegr8 » Wed Mar 30, 2016 8:27 pm

Im baffled. Battery was low after testing and running some fresh wire. I got 10 volts at the contact in the socket with my negative touching the outer part of socket. Should have light. Ive plugged 4 different bulbs in and still no light, unless i squeeze brake lever or turn key to park. Guess i just wont ride at night lol.

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Bluewaterhooker0
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Motorcycle: 1997 Goldwing GL 1500 SE

Re: Only getting 6 volts to my tail light

Postby Bluewaterhooker0 » Wed Mar 30, 2016 9:23 pm

P8thegr8 wrote:Im baffled. Battery was low after testing and running some fresh wire. I got 10 volts at the contact in the socket with my negative touching the outer part of socket. Should have light. Ive plugged 4 different bulbs in and still no light, unless i squeeze brake lever or turn key to park. Guess i just wont ride at night lol.


I assume that 10V reading is lower than the battery voltage. It is possible to get a voltage reading with a VOM, that will not handle a load (power the light bulb). A VOM offers NO LOAD to the circuit. It reads only voltage potential. The symptom you describe sounds like a weak connection, unable to handle a load. I've come across this problem in my boat (corroded wires and connections), and also in my air conditioning business (same reasons). It drives you nuts because you are reading the voltage, but when connected, nothing will work. The 6V and 10V, plus your description of no light (under load) sound just like such a scenario. A wiring diagram would help immensely. But, since a change of key position "fixes" the problem, you most certainly have a bad, loose, or corroded connection in the circuit that is powered in the 'ON' position. Apparently, the 'PARK' key position supplies power to the bulb through a different circuit, up to a point. You need to trace backward from the bulb, until you find where it is powered from 2 different sources. One of those sources will be from the key in PARK. The other will be the problem circuit. Then it's just a matter of finding the weak link in that circuit. Using a light bulb probe might be a much better diagnostic tool for this (instead of a VOM), as it will fail to light (just like your taillight) when you reach the weak link. I'm still betting on a wiring junction or relay as the cause of the issue. It's entirely possible that 2 different relays power that light, one in each of the 2 different key positions.

P8thegr8
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Joined: Tue Mar 29, 2016 9:07 pm
Location: Mason city, ia
Motorcycle: 1978 gl1000

Re: Only getting 6 volts to my tail light

Postby P8thegr8 » Wed Mar 30, 2016 10:00 pm

Thanks for the input blue Ill get the test light out tomorrow and start testing

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virgilmobile
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Re: Only getting 6 volts to my tail light

Postby virgilmobile » Thu Mar 31, 2016 10:14 am

Pay close attention to the fuseholders.Volts can be on the connector and not make it all the way to the other side due to a weak or corroded connection to the fuse.
With the key on,probe the fuse clip on both sides,not the end caps of the fuse.Even better would be to stab the wire feeding the fuse and leaving it.
Fuseholders can weaken or corrode.
The brown wire feeding the park lamps does come out of the ignition switch,through a fuse and then to the lamp.
Always test for volts under load..while trying to make it work.a unloaded circuit measured with a volt meter can give you erroneous information.
always test the circuit when it is failing to locate where its bad.

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virgilmobile
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Re: Only getting 6 volts to my tail light

Postby virgilmobile » Thu Mar 31, 2016 10:33 am

also keep in mind that there are 2 fuses for the rear "park" lamp.
One is called PARKING and the other is TAIL.
PARKING is a separate circuit in the ignition switch that feeds the tail lamp only.
Tail is the circuit that feeds all the park lamps,including the instrument cluster.
To my remembering,the park only circuit is a solid brown,The tail circuit (including the instrument lamps) I think is a brown with a white tracer.

P8thegr8
Posts: 5
Joined: Tue Mar 29, 2016 9:07 pm
Location: Mason city, ia
Motorcycle: 1978 gl1000

Re: Only getting 6 volts to my tail light

Postby P8thegr8 » Thu Mar 31, 2016 2:38 pm

You my boy blue got it narrowed down to somewhere between the fuse box and where the wire comes out from under the seat. If youre ever in north central Iowa I iwe you a steak and beer my friend thanks for your input virginmobile blue gog me pointed inthe right direction.. Everything i learned in electrical theory and basic wiring told me this light should wor I was starting to think black magic lol.

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virgilmobile
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Joined: Sun Sep 19, 2010 5:39 pm
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Motorcycle: 1988 GL1500 I
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78 GL1000
81 GL1100
82 GL1100 I
83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: Only getting 6 volts to my tail light

Postby virgilmobile » Thu Mar 31, 2016 3:40 pm

Its not black magic.Electric is black smoke.
As long as you keep it contained it gets to where its suppose to go.Just don't let it leak out or get slowed down.
:lol:

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Bluewaterhooker0
Posts: 556
Joined: Wed Nov 14, 2012 11:27 pm
Location: Tampa, Fl
Motorcycle: 1997 Goldwing GL 1500 SE

Re: Only getting 6 volts to my tail light

Postby Bluewaterhooker0 » Thu Mar 31, 2016 6:39 pm

As long as you don't learn electric the way this guy did.....you're OK




froche
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Location: Vista, ca
Motorcycle: 1985 Goldwing Aspencade (GL1200A

Former bikes;
2000 R1100RT
2005 Suzuki Bandit
1979 Yamaha XS1100
1978 Yamaha XS1100 Special
1990 Yamaha XV250
1980 Yamaha XV750
1979 Honda CB750
1968 Triumph Bonneville T120
1973 Honda CB450
1968 Harley Davidson Sportster
1974 Honda CB750
1968 Honda CL72

Re: Only getting 6 volts to my tail light

Postby froche » Fri Apr 01, 2016 6:25 pm

Quite the electronics engineer!!

P8thegr8
Posts: 5
Joined: Tue Mar 29, 2016 9:07 pm
Location: Mason city, ia
Motorcycle: 1978 gl1000

Re: Only getting 6 volts to my tail light

Postby P8thegr8 » Sat Apr 02, 2016 9:43 pm

Nope,I know how to build a fuctioning electric guitar. Cant play though.




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