Turn signal and headlights

S

shan rose

New member
May 11, 2009
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hey guys, got an issue with my left turn signal, but only at night. when I turn on the headlights, it fails to flash in the front, and the rear blinks
slower. I replaced the head light switch, and cleaned all the contacts, but this still has me baffeled. when the headlights are off it still functions
normally as does the right blinker. its only the left that does this. any thoughts?
--
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
 
Bad ground somewhere, Shan.

D C "Mac" Macdonald
Amateur Radio K2GKK
Since 30 November '53
USAF and FAA, Retired
Member GMCMI & Classics
Oklahoma City, OK
"The Money Pit"
TZE166V101966
'76 ex-Palm Beach
k2gkk + hotmail dot com

________________________________
From: Gmclist on behalf of Shan Rose
Sent: Wednesday, December 20, 2017 16:32
To: gmclist
Subject: [GMCnet] Turn signal and headlights

hey guys, got an issue with my left turn signal, but only at night. when I turn on the headlights, it fails to flash in the front, and the rear blinks
slower. I replaced the head light switch, and cleaned all the contacts, but this still has me baffeled. when the headlights are off it still functions
normally as does the right blinker. its only the left that does this. any thoughts?
--
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA

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yeah I figured that was probably the case, got an idea where to look first?
--
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
 
There are three possible causes.
1 . corroded or loose contacts on bulbs. Remove bulbs one at a time and clean them and spray in some contact cleaner.
2. A broken filament inside a bulb that might be dangling and shorting out.
You can check 2 as you are checking 1.
3. A bad ground. Likely the one in the rear on the inside wall beneath the area of the license plate. That ground is a cluster with about six or eight wires attached. The license plate holder often leaks water to the inside which runs down and rusts the ground cluster. There is a similar ground in the front inside corner by the driver but that is less likely to be the problem
Check all turn signal bulbs including the ones on the side.

Emery Stora
77 Kingsley
Frederick, CO

>
> Plastic front and rear end caps.
> Jim Hupy
>

>>
>> yeah I figured that was probably the case, got an idea where to look first?
>> --
>> 73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
>>
>> _______________________________________________
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I did not mean to say that these are the only possible causes but are a good place to start looking.

Emery

>
> There are three possible causes.
> 1 . corroded or loose contacts on bulbs. Remove bulbs one at a time and clean them and spray in some contact cleaner.
> 2. A broken filament inside a bulb that might be dangling and shorting out.
> You can check 2 as you are checking 1.
> 3. A bad ground. Likely the one in the rear on the inside wall beneath the area of the license plate. That ground is a cluster with about six or eight wires attached. The license plate holder often leaks water to the inside which runs down and rusts the ground cluster. There is a similar ground in the front inside corner by the driver but that is less likely to be the problem
> Check all turn signal bulbs including the ones on the side.
>
> Emery Stora
> 77 Kingsley
> Frederick, CO
>

>>
>> Plastic front and rear end caps.
>> Jim Hupy
>>

>>>
>>> yeah I figured that was probably the case, got an idea where to look first?
>>> --
>>> 73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
>>>
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>>
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What happens lot ofthe time is that the socket that is stamped inti the
metal housing looses contact at that point.
We sometimes solder a bridge there.

> I did not mean to say that these are the only possible causes but are a
> good place to start looking.
>
> Emery
>

> >
> > There are three possible causes.
> > 1 . corroded or loose contacts on bulbs. Remove bulbs one at a time and
> clean them and spray in some contact cleaner.
> > 2. A broken filament inside a bulb that might be dangling and shorting
> out.
> > You can check 2 as you are checking 1.
> > 3. A bad ground. Likely the one in the rear on the inside wall beneath
> the area of the license plate. That ground is a cluster with about six or
> eight wires attached. The license plate holder often leaks water to the
> inside which runs down and rusts the ground cluster. There is a similar
> ground in the front inside corner by the driver but that is less likely to
> be the problem
> > Check all turn signal bulbs including the ones on the side.
> >
> > Emery Stora
> > 77 Kingsley
> > Frederick, CO
> >

> >>
> >> Plastic front and rear end caps.
> >> Jim Hupy
> >>

> >>>
> >>> yeah I figured that was probably the case, got an idea where to look
> first?
> >>> --
> >>> 73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
> >>>
> >>> _______________________________________________
> >>> GMCnet mailing list
> >>> Unsubscribe or Change List Options:
> >>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >>>
> >> _______________________________________________
> >> GMCnet mailing list
> >> Unsubscribe or Change List Options:
> >> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
> _______________________________________________
> GMCnet mailing list
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--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502
 
> What happens lot ofthe time is that the socket that is stamped into the metal housing looses contact at that point.
> We sometimes solder a bridge there.
>
> --
> Jim Kanomata
> Applied/GMC, Newark,CA
> jimk
> http://www.appliedgmc.com
> 1-800-752-7502

Stan,

I went around this loop with three of my four corners. At least one had the problem Jim describes.

I was finally successful when I tinned the socket and attached an new ground wire to something that was a good ground. This worked so well that I did
it to the next two without even bothering to locate the actual problem.

Part of my problem started when grandsons were ripping icicles off the "housetruck" in spite of being told to leave it alone.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
My schematic for 77 & 78's shows the headlights and turn-signals share a common grounding point. I'm thinking a 73 is likely the same. You could
spend a bunch of time tracing down the wiring to the ground point... or you could just splice in a new wire from the ground wire on the headlights and
run it to a new grounding point.

Do both headlights while you are at it. My schematic shows the ground on the headlights as being a #14 black wire.

Also (with the lights OFF!) take out the park-lights/directional signal bulb and clean the base and socket with some steel wool.
--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
Hubler 1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
Bad ground in the left front. That's why it doesn't work when the headlights are on...there is power on the other side of the load. The rear flashes
slower because the load on the flasher from the front is not there anymore when the headlights (or actually just the parking/running lights)are on.
Otherwise there is enough of a ground present through other lights on the circuit to make the turn signal work in the front and flash at the normal
rate.
--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.
 
Does your left front marker light work? I thought the marker light and front turn signal share part of the circuit.

> hey guys, got an issue with my left turn signal, but only at night. when I turn on the headlights, it fails to flash in the front, and the rear
> blinks slower. I replaced the head light switch, and cleaned all the contacts, but this still has me baffeled. when the headlights are off it still
> functions normally as does the right blinker. its only the left that does this. any thoughts?

--
Vadim Jitkov
'76 Glenbrook 26'
Pullman, WA
 
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