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Old 09-12-2017, 04:24 PM   #1
dmf6978
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Default Tailight Bulb Socket Question

As you can see the right bulb barely is turning on, but the left side is bright as hell. I replaced both bulbs with fresh ones, and I have the double contacts. I bought a replacement socket from IHA but from the picture it looks wrong and doesn't square up with the one I have. Do you think it could be the contacts or something deeper than this? I found used ones on Ebay and want to snatch them up but would prefer if someone had some insight as what the issue could be. The bulbs are seated tight but not super bright. Then on the new IHA part there is no way for the bulb to lock in. I suspect it was meant to be for a scout ad not my 67 1200B pickup.
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Old 09-13-2017, 09:43 AM   #2
Scoutboy74
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Default Re: Tailight Bulb Socket Question

I suspect you have a grounding and/or wiring gremlin. You're dealing with a dual filament bulb setup. The dim filament is meant to receive the constant signal from your parking/tail light feed when actuated by the headlight switch, while the bright filament is meant to receive the momentary directional/4 way hazard/stop-brake feed. The rear lighting hardware is completely identical/interchangeable between the fullsize pickalls and Scout 80/800 models of similar year range. So the parts you received from IHPA shouldn't be the issue.
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Old 09-13-2017, 12:54 PM   #3
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Default Re: Tailight Bulb Socket Question

If you haven't done so already, I'd do a simple sanity check and swap the bulbs to eliminate a bad bulb issue. Nowadays new doesn't seem to mean s**t. If that checks out OK, take a voltmeter and see what you have at the two hot contacts inside the sockets with lights removed and the switch on, and then use an ohm meter to look at the grounds with the lights turned off.
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Old 09-13-2017, 01:10 PM   #4
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Default Re: Tailight Bulb Socket Question

Yep. And for this type of diagnosing, you really don't need anything more expensive or sophisticated than an incandescent probe with gator ground clip. This is go/no-go stuff. Actual voltage readings at the back lights really aren't that critical. When you probe a light socket terminal with the ground clip attached to where the light housing is grounded and that makes test bulb light up nice and bright, you've got a complete circuit. Move on to the next one.
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Old 09-17-2017, 04:06 PM   #5
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Default Re: Tailight Bulb Socket Question

Thanks for the few tips. For a second I thought no on was answering, but I guess I didn't get the alerts. I will meter it out. What would I have to do then if it is a ground or wiring issue? Get under the truck and trace the wires back? I assume that the left side and right side are not wired together but separate back to the fuse panel or main harness
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Old 09-17-2017, 04:22 PM   #6
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Default Re: Tailight Bulb Socket Question

For a wiring issue, yeah, you trace it back as far as necessary until the problem is found. The socket housings take their ground from metal on metal contact with the body as secured by sheet metal screws. Loosen, remove, cleanse surfaces of grit and rust and refasten.
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Old 09-18-2017, 02:23 AM   #7
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Default Re: Tailight Bulb Socket Question

Cool. thanks for the tips. See if I can resolve this myself.
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Old 09-18-2017, 07:18 AM   #8
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Default Re: Tailight Bulb Socket Question

Sure. Start with the ground work first. Its the easiest and a vast majority of vintage auto electrical issues turn out to be ground related anyway.
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Coal Trickle - '99 Dodge Ram 2500 Q-Cab SWB 4x4 - 5.9L 24V CTD/NV4500
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Mongo - '71 1210 Std Cab 2WD - 345/TF727/RA17 D60 4.10 Trac-lok - "Mongo love candy! Duh, huh, huh!"
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Old 09-24-2017, 02:39 AM   #9
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Default Re: Tailight Bulb Socket Question

You guys are the best. It was surely a grounding issue. I think I need to get new screws and clean out those holes. When i move the housing around the bulb goes super bright then dims. Will need to spend more time on this, but I understand how it works. Next up is fuel and brakes.
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Old 09-24-2017, 06:41 PM   #10
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Default Re: Tailight Bulb Socket Question

Star washers under the screw heads will help.
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