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Old 10-23-2018, 09:17 AM   #1
jfnar
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GMC headlight upgrade issues

I originally posted this in ELECTRICAL but got no response so I'll try it here.

I recently upgraded the headlights on my 68 GMC with the Hella 002850811 kit (https://www.amazon.com/HELLA-0028508.../dp/B001G7A9YS). I only changed the outside two lights and I did not upgrade the wiring or add relays, though I plan to someday. The improvement over the old lights is very noticeable but I have one issue. When driving with the brights on the lights will intermittently go off for a split second. It varies from a flicker to going completely dark for a full "Mississippi." It never did this with the old lights and it still doesn't do it when on dim. Last night I made a test drive and kept one eye in my side mirror to see if the side markers flickered when the lights did but they did not. It's not a daily driver so I'm not going to drive it at night until I get this fixed. Any suggestions will be greatly appreciated.

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Old 10-23-2018, 10:05 AM   #2
davepl
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Re: GMC headlight upgrade issues

I don't know what the load is but the headlights are driven through an auto-reset breaker that I bet you're tripping. You need a proper relay in there.
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Old 10-23-2018, 11:59 AM   #3
Zeroman
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Re: GMC headlight upgrade issues

^^^^^What he said^^^^^

Those headlights pull more amps than standard ones, overloading the circuit.

Install a proper headlight harness with the relays. This will power the headlights right off of the battery, not through the headlight switch.
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Old 10-23-2018, 07:28 PM   #4
jfnar
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Re: GMC headlight upgrade issues

10-4. I've got the relays on order. Thanks for the advice.
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Old 10-23-2018, 08:24 PM   #5
CRUSH2.0
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Quote:
Originally Posted by jfnar View Post
10-4. I've got the relays on order. Thanks for the advice.
Let me know your final setup as I want to copy it!!!!
Thx
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Old 10-23-2018, 09:11 PM   #6
Fbks_Cruiser
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Re: GMC headlight upgrade issues

What wattage H4 bulbs did you use? Standard H4s are 55/60W and can go much higher. I believe the stock were closer to 35W. The higher wattage would trip the breaker.
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Old 10-23-2018, 10:35 PM   #7
dmjlambert
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Re: GMC headlight upgrade issues

So there were auto-reset breakers in 68 in the headlight circuits of GMC?
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Old 10-23-2018, 11:58 PM   #8
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Re: GMC headlight upgrade issues

Quote:
Originally Posted by Fbks_Cruiser View Post
What wattage H4 bulbs did you use? Standard H4s are 55/60W and can go much higher. I believe the stock were closer to 35W. The higher wattage would trip the breaker.
Jegs website says those are standard H4 12V 60/55W Bulbs.

OP, you might consider upgrading the inner (high beam only) lamps to E-codes also. These Hellas use H1 bulbs and being dedicated high-beams, should easily outperform your H4s, which have to perform the separate duties of low beam and high beam. http://www.rallylights.com/h5001-hel...dlamp-kit.html


Google might find others (I didn't look). I would stick with an established European brand with proven quality, such as Hella or Cibie.
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Old 10-24-2018, 11:15 AM   #9
jfnar
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Re: GMC headlight upgrade issues

This is what I have on order: https://www.classicindustries.com/product/mx01133.html
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Old 11-08-2018, 05:27 PM   #10
jfnar
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Re: GMC headlight upgrade issues

The first harness that came in was incorrect. Even though the packaging said "4 headlights" it was actually for a 2 headlight set up. Classic Industries promptly sent the correct one and I spent a little time the last couple nights installing it. It did indeed take care of the problem. I drove about 5 or 6 miles last night and did not see even a flicker. Now I just need to spend a little time getting the lights aimed a little better and all will be good in the headlight department. Thanks for all the help.
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Old 11-09-2018, 01:12 PM   #11
Andy4639
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Thumbs up Re: GMC headlight upgrade issues

I have installed several head lights with the relays installed and all I'm going to say is no matter what anyone else says... always, always install the relays.

The relays will take the amps off the whole system and make everything last longer. Even if you install a brand name wiring harness install the relays.
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