Headlight voltage trouble

Tech tips and how to's

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jayedeluxe
Roadster Nut
Posts: 47
Joined: Sun Apr 12, 2020 3:50 pm
Location: san diego
Model: 2000
Year: High Windshield-68-70

Headlight voltage trouble

Post by jayedeluxe »

So I have my 1970 2000 back from paint and am now putting it back together. Having an issue with voltage to rightside headlight. Left side gets approx 11v or so and is plenty bright. Right side only gets approx 9v and is very dim. I'm suspecting a poor ground but cannot find where the headlight wire cluster goes to ground. Left side must have a good ground, but aren't they tied together before going to ground ? Thanks !
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jayedeluxe
Roadster Nut
Posts: 47
Joined: Sun Apr 12, 2020 3:50 pm
Location: san diego
Model: 2000
Year: High Windshield-68-70

Re: Headlight voltage trouble

Post by jayedeluxe »

don't know why the image is upside down !!!!
Erock311
Roadster Newby
Posts: 13
Joined: Wed Aug 31, 2016 1:19 am

Re: Headlight voltage trouble

Post by Erock311 »

I used to have this every so often on my 510, move fuses for headlites back and forth in the clips, or clean clips. Cheap fix, hopefully will fix problem.
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Curtis
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Joined: Fri Jan 01, 2010 2:49 pm
Location: Des Moines, WA
Model: 1500/1600
Year: Low Windshield-64-67.5

Re: Headlight voltage trouble

Post by Curtis »

66 stroker, almost done.
67 basket case, paint coming soon.
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Curtis
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Posts: 3421
Joined: Fri Jan 01, 2010 2:49 pm
Location: Des Moines, WA
Model: 1500/1600
Year: Low Windshield-64-67.5

Re: Headlight voltage trouble

Post by Curtis »

Ignore the wire gauge call outs, they need to be fixed.
66 stroker, almost done.
67 basket case, paint coming soon.
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redroadster
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Joined: Tue Mar 12, 2013 10:58 am
Location: KCMO
Model: 1500/1600
Year: High Windshield-68-70

Re: Headlight voltage trouble

Post by redroadster »

Do a voltage drop tests may isolate the weak Conn. I cover the wire to Brass crimp with solder. You need bright steel to get a good Conn.
Or a star washer
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jrusso07
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Posts: 1481
Joined: Sat Aug 02, 2008 9:02 am
Location: Penn Yan, NY
Model: 2000
Year: High Windshield-68-70

Re: Headlight voltage trouble

Post by jrusso07 »

Also, check the brass rivets on the back side of the fuse holders (back side of fuse box). They can get loose over time. Here is a excerpt from the tech wiki

"First, note that 1970 is DIFFERENT than prior years! On 1970, there are TWO fuses, one for each bulb, and +12 is fed to the 'common' (what you'd expect to be ground) terminal. To activate the lights, the hi or lo contact is brought to ground. So if you're using different bulbs, be careful as some of the HO stuff has the 'common' terminal grounded as part of its construction.

On the '68 especially, the fusebox tends to have a problem and cook the single headlight fuse. From what I can tell, there's slight resistance between the brass clip itself and the brass rivet. That point heats up, burns wires on the back and melts the fuse on the front. Several of us have ultimately installed a separate fuse that bypasses this one on the fuseblock".
Joe

1969 SRL311 - Solex
1970 SPL311 - U20 mod
1970 SRL311
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dbrick
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Re: Headlight voltage trouble

Post by dbrick »

I might have a spare late fuse box, somewhere if yours is bad. The late 2 fuse headlights are wired completely ass backwards, + from each fuse feeds the common terminal of the headlight, and the 2 ground wire run from high and low terminal of both headlights to the highbeam relay, which sends ground to the selected filament to power the light. Bad ground at the relay can be an issue.

Dave Brisco

Take my advice, I'm not using it"

66 2000 The Bobster
64 1500 in pieces for sale
1980 Fiat X1/9
2009 Volvo C-70
08 Expedition EL, STUPID huge but comfy
1962 Thompson Sea Lancer, possible money pit