425 Headlight Problem

825 Views 5 Replies 2 Participants Last post by dixie460, Jan 24, 2022

Stocks425

Discussion Starter · Jan 24, 2022

First time poster here so go easy….

Have a first production year 425. Bought it used in good condition last year. Everything functioned properly and continued to do so until today when I attempted to install LED headlights. No issues with removal and install of Phinlion 3600 Lumens 1156 LED bulbs. Selected these bulbs as their size was compatible, light output was tremendous, and they draw less than 1 Amp.

Turned key to accessory position and hit the light switch. Lights flickered twice then nothing. Removed bulbs thinking maybe I blew them as polarity may have been different in the bulb housing and not compatible with the LEDs. Checked LED bulbs with 12 V battery and pigtails - worked fine so not blown. Put original incandescent bulbs back in and now they don’t work either - what??

Immediately checked light fuse - it was good. Checked for power at bulb assembly with switch on and key in accessory position - no power there. Pulled light switch. Had power there with key in accessory position. Resistance across switch was about 1 Ohm which seemed high. Then checked resistance from switch base to the headlight assembly and got 7 Ohms which also seemed high.

I’m at a loss here. I’m not aware of anything downstream of the switch other than the harness and bulb housing that could be the culprit. Maybe I developed a short? If so, wouldn’t fuse have blown? Any ideas on what the issue could be?

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dixie460

· #2 · Jan 24, 2022

Hey, welcome to GTT!

You have a faulty connection somewhere. The 1 ohm across the switch ain't particularly good but it ain't terrible either. The 7 ohms across the harness between the switch and lamp sockets does indicate a problem between those two points.

Check all wiring, don't forget the grounds too. Pay special attention to anything in the vicinity of where work was recently performed.

I actually had a novel written here explaining how faulty connections or switches can show good voltage under no load but not pass current when loaded, but let's start simple first.

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Stocks425

Discussion Starter · #3 · Jan 24, 2022

dixie460 said:
Hey, welcome to GTT!

You have a faulty connection somewhere. The 1 ohm across the switch ain't particularly good but it ain't terrible either. The 7 ohms across the harness between the switch and lamp sockets does indicate a problem between those two points.

Check all wiring, don't forget the grounds too. Pay special attention to anything in the vicinity of where work was recently performed.

I actually had a novel written here explaining how faulty connections or switches can show good voltage under no load but not pass current when loaded, but let's start simple first.

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Stocks425

Discussion Starter · #4 · Jan 24, 2022

Thanks dixie460. I’m going to check grounds tonight, clean terminals, maybe run a temp wire from switch to light housing in hopes of narrowing this down. Hopefully I find the problem.

The harness on the frame transitions from what appears to be a PVC wire wrap (clearly factory) to the split corrugated plastic wire wrap under the grill. The split wrap is zip tied on the wires and while it looks to possibly be the factory wiring, the transition in wire wrap type has me suspicious. I’m wondering if there isn’t some prior homeowner work hidden under the split wire wrap that should be investigated. The only thing I can think of is me removing the light housing maybe stressed a poor wire connection in that area.

More probing and tracing tonight

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Stocks425

Discussion Starter · #5 · Jan 24, 2022

Took off the plastic wire wrap which transitions to a braid type wrap under the grill. Found no connections or other suspicions the wiring/work is not factory. Checked grounds and they were good. Checked continuity to the switch and it was now good. Put in a bulb and hit the switch and now the lights work. Put everything back together with new bulbs and still have functioning lights. I did clean all connection spades, so maybe that was it. Only concern is there is a partial break in the light wire in the harness somewhere and me moving the wire around restored continuity. My fear is this success is only temporary and I’ll be tearing apart the harness in the future. For now, success.

Thanks for the help dixie460 - your advice was spot on.

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dixie460

· #6 · Jan 24, 2022

You're welcome! Glad everything is working for you now!

More likely than a partially broken wire is a loose connector terminal or pin, perhaps just give those a wiggle to test.

Edit: fixed spelling.

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