The Stovebolt Site Forums The Shop Area The Electrical Bay Dimmer light stays on low beam

My dimmer light indicator goes bright when on high beam and dims on low beam ... will not extinguish on low beam. New wiring harness and new dimmer switch. Any ideas?

Bad ground at the tail lights? There are so many ways to back feed a light. Bad grounds are the common issue.

OK thanks Steve I'll check that .... every thing else is working fine ... just this one little annoying thing.

OK thanks Steve I'll check that .... every thing else is working fine ... just this one little annoying thing.

Ground at tail lights was not it. Still baffled.

defective dimmer switch [new or not!] .... crossed wires on one of the head lights [one high, one low on at the same time] .... plug assembly along the way with some stray bit in it that shorts between the indicator wire and something else, like park light wire .... using a meter you may be able to track where voltage to the indicator is coming from when on low beams, check any accessible point back to where the wire ties into the high beam wire at the dimmer switch

Bill

You may want to have a look at this post. headlight indicator problems

Thanks Guys .... A lot of good ideas and likely causes... will let you know how this works out.

The dimmer switch lives in a very hostile environment- - - -right there where splash from the front wheel lands. If you're in an area where a lot of salt gets used on the road, all sorts of junk gets sprayed onto the switch and its wiring. Start looking for problems there.
Jerry

OK.. So i disconnected headlight Hi beam at the fender well terminal block...turned on low beam and got 8.5v coming back on the Hi beam wire from the headlight.... tried each light separately ... No Cigar. Then ran ground from driver headlight to pass headlight then on to battery negative. No Cigar! Checked the wire positions on the headlights .. even switched one around ... no help just worser. So if this is a grounding issue can I go to each grounding point on the truck and jumper them all back to the Battery ground strap ... would I eliminate the elusive ground problem... and then work backwards to find the culprit? Dimmer switch is new, wiring is new and truck has added turn signals and truck has never been driven in the rain.

"disconnected headlight Hi beam at the fender well terminal block ... turned on low beam and got 8.5v coming back on the Hi beam wire from the headlight"

so you're saying that with the low beam powered and high beam terminal disconnected, you're getting a voltage reading at the high beam terminal? have you changed the headlight bulbs? are you sure the headlight pigtail connectors are good? with the connectors off the bulb, resistance check between the terminals, and resistance check the bulb terminals

Bill

Hi Bill .. Yes ...only feeding in Lo beam power and then seeing the 8.5 volts coming back from the headlight. The bulbs are new ... seeing the same thing on both lights ... disconnected the driver side bulb connector and repeated the test but then no power going back up the high side ... and the connectors are new and good. Have not checked resistance on the bulbs yet... will do though.

Saw this once on a 54 1/2 ton. New buckets assembled from the vendor. Problem was the new 4 position strips on the fender. One is high, One is low, One is running light, one is turn signal. Ground is a screw into the inner fender. He had put the ground on the strip and it made a lot of funny stuff happen. Ground is to the inner fender. Bolts to the cab and a strap to the starter mount bolt, and a strap to the negative on the battery from the mount bolt on the stomp starter. pretty straight forward. I did not catch the ground on the strip for a little while, it looked OK so my eyes slid right over it. Standard 3 prong plug is from the back Hi on the left, ground in the middle top, and low on the right. I think, anyway there should be no volts back out from a light that is working. All voltage should drop across the working filament to ground. 8.5 volts will light up the dash light, just sorta dim, like what you have. So start with the wires from the lights. one wire at a time.

So I checked resistance across HiLo, HiGrnd, LoGrnd .. all the same at 0.5 OHMS.. 0 resistance from inner fender to engine grounding strap and frame. Sure 'nuff confused.