Bit by LMC again - The 1947 - Present Chevrolet & GMC Truck Message Board Network

lutronjim · 08-08-2017, 10:13 PM

I installed a heavy duty headlight harness and light from LMC 'bout 6 months ago. Worked great till a month ago. Pushed dimmer button for brights and got nothing. By the time I got home brights were working again. Since I had bright light indicator, I didn't think it was dimmer switch. Happened again tonight - shot it to relay.

Anyone know if there is a none Chinese relay that will fit LMC plug?

Thanks Going out of town this weekend and need to get fixed.

lsversaw · 08-09-2017, 05:04 PM

This is one of the drawbacks of the relay-operated "heavy duty" headlight harness; if one of the relays fail, you have no high beams or no low beams.

But I hate to replace parts before I'm sure it will solve a probleam, and there is a possibility that there is a bad connection at one end of the wire from the dimmer switch to the high beam relay. This wire is part of the harness assembly provided by LMC (just sayin'). Connectors are the second most unreliable part -- after mechanical/electrical parts like soleniods and relays -- in wiring systems. If the connector blade that goes to the high beam relay is loose in the housing, or poorly attached to it's wire, at either end, it could explain the intermittent symptoms you see. To test the wire, turn the headlights on and select high beams. Then wiggle the connector that attaches to the dimmer switch, and the connector that attaches to the high beam relay. If the high beams don't flicker or go out, then you're probably correct in thinking the high-beam relay is bad. However, just to be sure, swap the high-beam and low-beam connectors between relays, so the former high-beam relay is now the low-beam, and vice-versa. If the problem moves to the low beams, you know for sure it's the relay.

I'm not familiar with the relays used in the LMC harness, but they probably have a standard pin layout that's common to many relays. If you can post some pictures of the relays, showing the pin layout, someone here can answer your original question, i.e., how to buy a higher-quality replacement relay.

I think you could make a case for running only the high beams through a relay, with no relay on the low-beam side, but that's really just a different set of tradeoffs. Any other opinions on this?

I think it would also be a good idea to mount a spare relay for a quick fix on the side of the road when one fails.

Good luck and let us know what you find.

ACK · 08-09-2017, 05:19 PM

Got my headlight relays from the junk yard, cost next to nothing and they're high quality. Like lutronjim posted, as long as they're standard relays, shouldn't be hard to find.

lutronjim · 08-10-2017, 08:21 AM

LMC has replacement relays on their site - if you want more of the same.

Found it was relay by swapping them.

I went to Summit and got a couple of spst relays. Had to solder and shrink rap new connectors. They have 5 pin connectors which seem to be standard on most relays. These have normal off and on - so I just clipped the normal on wire.

Using non relay low's would go back to using under gauge wire. I wouldn't think that would be good with the high amp blubs.

08-08-2017, 10:13 PM	#1
lutronjim Registered User Join Date: Dec 2013 Location: Dunwoody,Ga Posts: 443	Bit by LMC again I installed a heavy duty headlight harness and light from LMC 'bout 6 months ago. Worked great till a month ago. Pushed dimmer button for brights and got nothing. By the time I got home brights were working again. Since I had bright light indicator, I didn't think it was dimmer switch. Happened again tonight - shot it to relay. Anyone know if there is a none Chinese relay that will fit LMC plug? Thanks Going out of town this weekend and need to get fixed.

08-09-2017, 05:04 PM	#2
lsversaw Registered User Join Date: Aug 2013 Location: McPherson, KS Posts: 86	Re: Bit by LMC again This is one of the drawbacks of the relay-operated "heavy duty" headlight harness; if one of the relays fail, you have no high beams or no low beams. But I hate to replace parts before I'm sure it will solve a probleam, and there is a possibility that there is a bad connection at one end of the wire from the dimmer switch to the high beam relay. This wire is part of the harness assembly provided by LMC (just sayin'). Connectors are the second most unreliable part -- after mechanical/electrical parts like soleniods and relays -- in wiring systems. If the connector blade that goes to the high beam relay is loose in the housing, or poorly attached to it's wire, at either end, it could explain the intermittent symptoms you see. To test the wire, turn the headlights on and select high beams. Then wiggle the connector that attaches to the dimmer switch, and the connector that attaches to the high beam relay. If the high beams don't flicker or go out, then you're probably correct in thinking the high-beam relay is bad. However, just to be sure, swap the high-beam and low-beam connectors between relays, so the former high-beam relay is now the low-beam, and vice-versa. If the problem moves to the low beams, you know for sure it's the relay. I'm not familiar with the relays used in the LMC harness, but they probably have a standard pin layout that's common to many relays. If you can post some pictures of the relays, showing the pin layout, someone here can answer your original question, i.e., how to buy a higher-quality replacement relay. I think you could make a case for running only the high beams through a relay, with no relay on the low-beam side, but that's really just a different set of tradeoffs. Any other opinions on this? I think it would also be a good idea to mount a spare relay for a quick fix on the side of the road when one fails. Good luck and let us know what you find. __________________ Scott 1972 C20 long-wide. 350/350, Cheyenne Super, wood bed, PS, PB, dual batteries, dual tanks, leaf springs, gauges. No significant rust. No significant paint. 1971 C10 short step. Originally a 250/3ott with no options, now a 350/4L80. I purchased it already restored; only needs about 300 little details fixed.

08-09-2017, 05:19 PM	#3
ACK Registered User Join Date: Oct 2012 Location: Philly, PA Posts: 535	Re: Bit by LMC again Got my headlight relays from the junk yard, cost next to nothing and they're high quality. Like lutronjim posted, as long as they're standard relays, shouldn't be hard to find. __________________ My truck ain't dead, it just smells funny.

08-10-2017, 08:21 AM	#4
lutronjim Registered User Join Date: Dec 2013 Location: Dunwoody,Ga Posts: 443	Re: Bit by LMC again LMC has replacement relays on their site - if you want more of the same. Found it was relay by swapping them. I went to Summit and got a couple of spst relays. Had to solder and shrink rap new connectors. They have 5 pin connectors which seem to be standard on most relays. These have normal off and on - so I just clipped the normal on wire. Using non relay low's would go back to using under gauge wire. I wouldn't think that would be good with the high amp blubs.



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