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#1 |
Junior Member
![]() Join Date: Feb 2023
Location: Brooklyn Park, MN
Posts: 24
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Headlights cut out completely after hitting high beam dimmer switch
Took my 71 C20 out for a stroll around the block this evening.
When I hit the dimmer switch for the high beams - the headlights cut out completely. All other lights are working fine. I didn't dig into the issue tonight. I plan to get back out there tomorrow and see if I can track down a faulty wire or ground. Any ideas?
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awbanks 1971 C20 Longhorn |
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#2 |
Post Whore
![]() Join Date: Feb 2016
Location: Portland Oregon
Posts: 11,137
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Re: Headlights cut out completely after hitting high beam dimmer switch
I would start troubleshooting at the highbeam switch. It's common for the terminal connections on the switch to corrode and then the overheat the wiring.
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Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. ![]() RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377 |
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#3 |
20' Daredevil (Ret)
![]() Join Date: May 2003
Location: Jefferson State
Posts: 13,635
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Re: Headlights cut out completely after hitting high beam dimmer switch
x2 -- the dimmer switch on the floor, aka highbeam switch, lives in a poor environment and is a common failure spot.
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- Mike - 1972 K20 LWB 350/350/205 RIP El Jay |
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#4 |
Registered User
Join Date: Jul 2007
Location: Toppenish, WA
Posts: 15,507
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Re: Headlights cut out completely after hitting high beam dimmer switch
If you have higher wattage Halogens in the truck the dimmer switches don't survive well.
I put relays on both low and high beam circuts on my 71 to cut down on the load through the switch (s) After replacing the switch about every four or five months but I am running 55/100 H-4 bulbs.
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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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#5 |
Registered User
Join Date: Sep 2016
Location: Ft Smith, AR
Posts: 565
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Re: Headlights cut out completely after hitting high beam dimmer switch
I would start by replacing the dimmer switch. They are like $5.
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#6 | |
Registered User
Join Date: Dec 2017
Location: Elkhart, Texas
Posts: 1,701
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Re: Headlights cut out completely after hitting high beam dimmer switch
Quote:
http://67-72chevytrucks.com/vboard/s...d.php?t=185856 and download the proper wiring diagram for your truck. Start with the dimmer switch, use a voltmeter or 12V test light to check for continuity, bad switches, bad/corroded connections, burned/broken wires, etc... |
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#7 |
Senior Member
![]() Join Date: Feb 2002
Location: Tucson, AZ USA
Posts: 7,270
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Re: Headlights cut out completely after hitting high beam dimmer switch
Yeah. LMC lists p/n: 36-0620 for $5.95.
Funny, I needed one right now -- last week -- and bought a Dimmer Switch from O'Reilly's for $26.38. [Incl tax, and w/ Mil Disc]. It was made by Standard and had a ''Lifetime Warranty.'' Still made in Taiwan. [P/N: STD DS72] The last one was from 7/17, so almost 5 years in a daily driver isn't bad for a part that gets stomped-on multiple times a night. awbanks: I had your exact gripe, and R&R'ed the Dimmer Switch and that got it. While you're down there inspect the wiring to the plug and terminals, but most likerly it's just the Switch.
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Every 25 years I like to rebuild that 292, whether it needs it or not. Last edited by '68OrangeSunshine; 03-30-2023 at 12:19 AM. |
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#8 |
Senior Member
![]() Join Date: Dec 1999
Location: Southern California
Posts: 2,806
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Re: Headlights cut out completely after hitting high beam dimmer switch
First thing I would do is check for 12v at the headlights.
From my experience with LMC that $6 switch will be the same or more than Orielly's after shipping, Then there is the issue if it is actually in stock and when they will ship. The 51 year old switch in my 72 still works. Funny how expectations have changed.
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Richard 1972 K10 Custom Deluxe SWB Fleetside My build https://67-72chevytrucks.com/vboard/...d.php?t=800746 |
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#9 |
Special Order
![]() ![]() Join Date: Nov 2004
Location: Mt Airy, MD
Posts: 85,859
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Re: Headlights cut out completely after hitting high beam dimmer switch
I've had good luck with replacing the dimmer switch first. That tends to be the most common cause of your issue. Or to put it differently, the most common sign of a bad dimmer switch is the headlights cancelled out when you hit hi-beams. Don't throw the original out until you see the new one was the fix. If by a less likely chance you have some other issue, you'd be best continuing use of the original. But, mostly likely when to remove that switch you will see it has become right crusty.
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"BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~ |
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#10 | |
Junior Member
![]() Join Date: Feb 2023
Location: Brooklyn Park, MN
Posts: 24
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Re: Headlights cut out completely after hitting high beam dimmer switch
Quote:
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awbanks 1971 C20 Longhorn |
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#11 | |
Junior Member
![]() Join Date: Feb 2023
Location: Brooklyn Park, MN
Posts: 24
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Re: Headlights cut out completely after hitting high beam dimmer switch
Quote:
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awbanks 1971 C20 Longhorn |
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#12 |
Registered User
Join Date: Oct 2006
Location: Sparks, NV
Posts: 18
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Re: Headlights cut out completely after hitting high beam dimmer switch
I fought exactly this on my 70 last year. Replaced the switch a couple times and it would work. And then not. And then would. Always lost hi beams. Is it original wiring? Or rewired? My truck was a full frame off, and I used an AAW kit to rewire. On the bulkhead block from the inside of the cab, the little metal tab that holds the terminal in the block was never sprung out enough to catch apparently on the hi beam terminal. So when the engine bay side of the bulkhead block was installed, it pushed that one back just enough that it would barely touch but vibrate a little and intermittently loose contact.
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1970 c10 swb fleetside. Frame off, 2.5/4" drop, LS1/4L60e, daily driver. |
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#13 |
Registered User
Join Date: Apr 2022
Location: Moorpark, CA
Posts: 757
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Re: Headlights cut out completely after hitting high beam dimmer switch
As mentioned, the dimmer switch on floor is most likely suspect. If it is lose, tighten the hold down screws.
IMHO installing a headlight relay harness is a good idea on any of the 50-70's cars, trucks. LMC sells one. Plug and play, no cutting any wires. It removes the full 12v load off the headlight switch, so headlights and ALL lights are brighter This is where I installed mine. Just drilled 2 holes to mount relays . |
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#14 |
Registered User
Join Date: Jan 2009
Location: South Carolina
Posts: 264
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Re: Headlights cut out completely after hitting high beam dimmer switch
Lost my headlights in 2011 at 5:30 A.M. My O.E. dimmer switch lasted 42 years . Paid $7 for a new one back then . Been fine ever since . Thanks
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#15 |
Registered User
Join Date: Feb 2000
Location: Center City, MN, USA
Posts: 3,254
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Re: Headlights cut out completely after hitting high beam dimmer switch
MN location. (Like me).
Most likely a green, furry dimmer switch connector. Step 1: Take the connector off the dimmer switch. Look at the connections. Step 2: Spray with contact cleaner. Step 3: Re-connect. You probably just fixed your headlights but I'd do more... Step 4: As 72SB points out, research this site for "Headlight Relay Upgrade" then roll your own or buy a pre-made wiring harness that uses relays to power your headlights instead of elevendy billion miles of 16 or 18 gauge GM stock wire. All those miles of stock, too small now dry and brittle wire only gets about 10.5 volts to your headlights. Using relays to drive your headlights with juice straight off the battery not only puts 14.something volts to your headlights making them brighter, it also saves on your headlight switch which is more money and a larger PITA to replace.
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'70 cab, '71 chassis, 383, TH350, NP205. '71 Malibu convertible '72 Malibu hard top Center City, MN |
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#16 |
Junior Member
![]() Join Date: Feb 2023
Location: Brooklyn Park, MN
Posts: 24
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Re: Headlights cut out completely after hitting high beam dimmer switch
Thanks everyone for the information! The wiring harness color graphic will be extremely helpful in the future.
It ended up being a faulty dimmer switch. Ended up going with Orielly Auto's replacement for now as 68OrangeSunrise stated and everything works great now. I did find that the headlight wiring will need some work up front as someone did a poor job of fixing the headlight wire at some point in time. I will look at adding a relay. This is why I love this forum! Thank you all for your wisdom and insight. ![]()
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awbanks 1971 C20 Longhorn |
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#17 |
20' Daredevil (Ret)
![]() Join Date: May 2003
Location: Jefferson State
Posts: 13,635
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Re: Headlights cut out completely after hitting high beam dimmer switch
Glad you got it fixed, and thanks for the update!
If / when you do the relay mod, you'll need two -- one for low beams, & one for high beams.
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- Mike - 1972 K20 LWB 350/350/205 RIP El Jay |
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#18 |
Registered User
Join Date: Aug 2015
Location: Los angeles
Posts: 160
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Re: Headlights cut out completely after hitting high beam dimmer switch
Just went through this. As others have said ,look at the dimmer switch. That was the problem on mine. I took mine apart and cleaned it. Works perfect now. I would try and repair original. They are well made. Good luck
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#19 | |
Senior Member
![]() Join Date: Feb 2002
Location: Tucson, AZ USA
Posts: 7,270
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Re: Headlights cut out completely after hitting high beam dimmer switch
Quote:
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Every 25 years I like to rebuild that 292, whether it needs it or not. |
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#20 |
Registered User
Join Date: Jan 2011
Location: Chattanooga, TN
Posts: 2,151
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Re: Headlights cut out completely after hitting high beam dimmer switch
Just FYI that switch is an AC Delco D808 and can be bought today on Amazon for $12. I don't know if the Delcos are any better than a generic parts store one, but it's an option.
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'83 K20-TPI '73 C10 '79 C10-ex-diesel(SOLD) '07 Tahoe(Son driving) '14 Suburban-DD '71 C10-current project |
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#21 |
Registered User
Join Date: Apr 2016
Location: Kirkland,WA
Posts: 65
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Re: Headlights cut out completely after hitting high beam dimmer switch
I had this happen on a road trip going through the mountains at night in my 69 Vette. After pressing on the high beam switch a few times the headlights worked again. Probably corrosion in the switch from not being used much.
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#22 |
Senior Member
![]() Join Date: Feb 2002
Location: Tucson, AZ USA
Posts: 7,270
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Re: Headlights cut out completely after hitting high beam dimmer switch
I'm going to pull apart the old one [from 2017] and see if it can be refurbished.
Looks like one of the 2 side tangs lost its angle and that allows the cap to come up higher than it should from spring pressure. In Arizona we see very little corrosion. But the Jimmy, because of its convertible nature has a lot more cabin leaks than the Stepside's cab, even though it's 3 years older.
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Every 25 years I like to rebuild that 292, whether it needs it or not. |
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