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#1 |
Registered User
Join Date: Jul 2008
Location: Eastern Oregon
Posts: 2,338
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Changed Alternator Now No Headlights ?
The bearings in the alternator on my 71 C20 where getting noisy so I swapped in one I had on the shelf. Now I have no headlights, any thoughts...
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71 C-20 07 Magnum RT AWD |
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#2 |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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You left a wire off.
![]() Changing the alternator shouldn't effect the lights. Look and see if you blew a fuse. Do you have any power at all? ![]()
__________________
1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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#3 |
Registered User
![]() Join Date: Jul 2007
Location: Toppenish, WA
Posts: 15,514
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Re: Changed Alternator Now No Headlights ?
I'd go with left a wire off but first take your test light and check both sides of the headlight fuse. You should have power to the fuse all the time and if you don't have power to the fuse start backtracking on the power feed.
Check any connection you took loose when and before you pulled the old alternator off to see if you left something off. Looks for non factory wires that may have been installed to bypass a suspect circuit and feed power to the lights that you may not have reconnected. Half of these trucks have an extra wire on them to run power to something because of bad connection that wasn't fixed to be the way it was designed.
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Founding member of the too many projects, too little time and money club. My ongoing truck projects: 48 Chev 3100 that will run a 292 Six. 71 GMC 2500 that is getting a Cad 500 transplant. 77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around. |
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#4 |
Registered User
Join Date: Jul 2008
Location: Eastern Oregon
Posts: 2,338
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Re: Changed Alternator Now No Headlights ?
Thanks guys ! Funny not many wires behind the alternator ? I do have marker and dash lights. I’ll start tracing wires....
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71 C-20 07 Magnum RT AWD |
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#5 |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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Dimmer switch!!!!
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1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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#6 |
Registered User
Join Date: Apr 2012
Location: Ocala,Fl
Posts: 733
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Re: Changed Alternator Now No Headlights ?
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#7 |
Registered User
Join Date: Jan 2007
Location: Puyallup, WA
Posts: 1,662
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Re: Changed Alternator Now No Headlights ?
x3 on the dimmer switch
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72 C10 lwb fleetside -stock 350/350 combo |
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#8 |
Registered User
Join Date: Apr 2011
Location: Fairview Park, Ohio
Posts: 1,031
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Re: Changed Alternator Now No Headlights ?
take a light 12v tester and see if you have power at the headlight socket with switch on. use body ground on tester and not the ground at socket.
could have knocked a ground off somehow. if no power, see if power comes out of switch for headlights.
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My build page http://67-72chevytrucks.com/vboard/s...d.php?t=764662 My cabinet building site http://www.cbcabinets.com Last edited by rockyrivermark; 12-17-2018 at 05:16 PM. |
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#9 |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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Power comes out of head light switch to dimmer switch in the floor. The dimmer splits the power to the low side and high side. Check the dimmer first thing.
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__________________
1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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