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Blown Headlites

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by BluThndr71JMMY, Jan 19, 2002.

  1. BluThndr71JMMY

    BluThndr71JMMY 1/2 ton status

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    Don't know what caused it -- I just turned a corner onto a sidestreet, tapped the hi-lo brites switch and Pop! The Brights went on then out, tapped again the lo-beams went out and my dimmer switch stopped clicking. All at about 0300 on my way to a buddy's -- had to camp out till dawn.Tonite I R &amp; R'd the dimmer Switch. Lights still dead. Parking lights function OK. Continuity on the two heads on driver's side was negative. Have to disassemble to get to Pass side lamps. What's burning my headlamps out? Why was this system never fused? A similar gripe happened last year. I replaced the front wiring harness, batt, alt and ext/reg and headlamps (GMC, all 4). Oh yeah. the heater was on in both cases.(?) <P ID="edit"><FONT class="small">Edited by BluThndr71JMMY on 01/19/02 12:24 AM.</FONT></P>
     
  2. Triaged

    Triaged 1/2 ton status

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    Headlights are NEVER fused. Most have self resetting circuit breakers but I don't know about our Blazers.

    '71 Blazer CST w/ a 400sbc, 4" lift, 36" Supper Swampers, and alot of rust
    <a target="_blank" href=http://community.webshots.com/user/triaged>See it Here </a>
     
  3. BluThndr71JMMY

    BluThndr71JMMY 1/2 ton status

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    Could a short in the dimmer stomp switch cause the headlights to fry? Or am I looking at regulator/alternator issues? Yes, I know in this vintage headlamp circuitry was hardwired -- it was just a rhetorical question. The dimmer switch was a Taiwanese POC from checker auto. Its clicker action gave out.Tomorrow I will get diagnostic with it -- I've been so swamped at work that I couldn't take time to get to it, just had to run the old pickup to get around in the dark.I got a new set of headlights today, just have to install them once I find my gremlin.
     
  4. Triaged

    Triaged 1/2 ton status

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    I don't see why it would happen...unless the hi and lo beams both went on at the same time (short in the foot switch like you said)...I would think your alt. would have to be putting out way to much voltage to cause your headlights to go (as in boiling over the battery kinda voltage). Good luck.

    '71 Blazer CST w/ a 400sbc, 4" lift, 36" Supper Swampers, and alot of rust
    <a target="_blank" href=http://community.webshots.com/user/triaged>See it Here </a>
     
  5. codagoshi

    codagoshi Registered Member

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    I recently repaired my lights which were on bright for 5 months. First replaced the dimmer switch, that wasnt it, then replaced the two fuses on each side of the radiator, that wasnt it, then there is a wiring loom that runs through the driver side fender right from the firewall, it shorted out, the dim lights, and my voltage meter.

    Jim Riley
    72 CST Blazer 4x4
     
  6. BluThndr71JMMY

    BluThndr71JMMY 1/2 ton status

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    Well Guys, I'm gonna take advantage of the warm afternoon here (Tucson) and R&amp;R my headlamps. Also look for shorts/opens in my new 1 year old M+H wiring harness.Saw an interesting "how -to" on &lt;&lt;Early Burb Club&gt;&gt; site about using relays to separate the hi-current draw of halogen lamps from the lighter guage wires and switches these old rigs have. [http://www.classictruckshop.com/clubs/earlyburbs/projects/head/lights.htm] Especially with a 4-eyes like a GMC.Get back to ya.&lt;P ID=edit&gt;&lt;FONT class=small&gt;&lt;EM&gt;Edited by BluThndr71JMMY on 01/20/02 10:53 PM.&lt;/EM&gt;&lt;/FONT&gt;&lt;/P&gt;<P ID="edit"><FONT class="small">Edited by BluThndr71JMMY on 01/22/02 03:57 PM.</FONT></P>
     
  7. BluThndr71JMMY

    BluThndr71JMMY 1/2 ton status

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    OK -- new headlights -- 2) H5001s, 2) H5006s. Added water to batt, about 8 oz. Checked volts to headlight sockets: 11.8vdc. Hi-Lo switch good. Headlamp harness grounding terminals to radiator wall sanded and remade. Tightened alternator fanbelt just for GP. So far, system works good. Ran over to checker auto for test and check. Batt, alt charging and diodes good. Everything's nominal but I seem to need new lights every year or so.(?) Eleven months for the last set.
     
  8. travis

    travis 1/2 ton status

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    Might be a good idea to carry a spare headlight or two just in case. I'd carry at least one so you can drive home.

    Just my 2 cents.
    Travis
     
  9. Klef72K5

    Klef72K5 1/2 ton status

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    When I built my Jeep I couldn't get the headlight to work at all. They worked before I unplugged everything. Well it ended up being the dimmer switch! I didn't think it would cause it!
    For your headlights burning out every 11 months or so. Do you think you might be off roading too much? You get to bouncing around alot you know!
    Best of luck!


    <a target="_blank" href=http://wsphotofews.excite.com/031/rw/Jo/og/t488200.jpg>http://wsphotofews.excite.com/031/rw/Jo/og/t488200.jpg</a>
     
  10. BluThndr71JMMY

    BluThndr71JMMY 1/2 ton status

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    I'm pretty sure it was an offshore off-brand dimmer switch. Made in Taiwan, sold in a Niehoff box at checker auto, the maker's mark on the bottom was "CUB". They just don't make them like they used to and I think as far as AC/Delco -- they just don't make them any more. The off shore units are made to minimal standards and must be burning out at the higher currents that Halogen lights draw. Check out the "Early Burb Club" link above. I got a nice eMail reply from Sylvania/Osram about this gripe and they may be sending me some spares. They said to measure the amperage draw on the headlights. H5001s should be pulling 3.5A @ 50W; H5006s -- 2.5A @ 35/35W in hi- and lo- functions.Funny, I run 2 Halogen "7 round headlights on the '68 C/10 and '67 K/10 sub and never had this problem (!?)Anyway it's almost all back together again (except for the chrome bezels, which are off until I've dialed in the perfect headlamp focus alignment -- cruising with a long #2 phillips on the dash).So if you don't hear from me on this subject, assume everything's cool.BlueThunder over and out.<P ID="edit"><FONT class="small">Edited by BluThndr71JMMY on 01/23/02 02:11 AM.</FONT></P>
     
  11. Steve_Chin

    Steve_Chin 1/2 ton status

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    I've got high powered headlamps and am using relays in a similar manner to what I think is probably outlined on that how-to. The reason I did that was because I fried the dimmer switch with the headlights and now have a separate fused connection with good battery power directly to the lights.
     
  12. BluThndr71JMMY

    BluThndr71JMMY 1/2 ton status

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    Thanks, Steve:The nice lady at Sylvania/Osram e-mailed me that the lows draw 2.5A @ 35w and highs draw 3.5 A @ 50w (in a perfect universe.) So I went downtown to an obscure ham surplus shop and bought a DC ammeter in the 15 amp range. (Radio Shack doesn't stock 'em anymore). Fabbed a test jig with terminals and a 3-prong headlamp plug and proceeded to test.Current thru the "stomp" SW: 4.6A on Blue wire-Lamp Check(starting from the driver's side)Current on lamp #1: 4.8A on Tan wire, 4.4A hi and 4.0A on lo on the Lt Green wire -Current on lamp #2: 3.7A (hi-beam only) -Current on lamp #3: unable to complete test as $15 ammeter started clicking and burned up. But meter froze at 4.1A.(!?) -Current on lamp #4: n/a -Oops!Could that indicate some shorting in the lamp wire harnesses behind the Batt box? The harness, an M&amp;H product, seemed pretty high grade when I put it on last year. And nothing looked out of place visually. Or maybe I just tortured a good ammeter to death in an environment it was never meant to face?Not the sort of results I'd want to fax back to Sylvania's customer service.I may have to go the bosch relay route -- I was gonna add some fog/driving lights in the near future anyway as soon as I figured how to anchor them inside the GMC grill so they peek out the slots just inboard of the headlamps. That set-up uses bosch relays.I'm really just trying to get my rig back to a stock, simple baseline without adding any extra gadgets until it's free of shorts, opens and other nasty surprizes. That means no tunes, no CB, no scanner, etc until it's clean.
     

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