Switches including integral dash light dimmer (rheostat) and circuitbreaker itself wear out over the years. Corroded wiring harness connections and neglected grounds will accelerate this. Try to find a good ole' NOS or NORS headlight switch from "back in the day" up to maybe the 1980s, these are of good quality but shouldn't cost much more if at all. That auction site should have them, NOSpartsltd, the usual suspects.

The key I found was (surprise!) good heavy ground cables and clean shiny bright SAE connectors, firewall connectors, battery connections.

To actually see where voltage is being lost, a "drop test" with headlights on, from the negative battery post to the negative headlight terminal will tell the tale it should be ideally around Zero. Then perform the same test from the positive terminal, this will be a bit higher. Should not exceed (total, both sides) about 0.4 tenths volt.

This is a tall order because the battery voltage must travel to solenoid to light switch, down to floor dimmer, all the way back out to driver and then passenger side headlight.

The headlight relays work excellent but are not a substitute for good solid clean tight grounds at block, frame, and firewall and associated wiring. Take the time to grind down to bright shiny metal at the block, frame, and firewall. Replace old, stiff, corroded grounding cables or straps.

I ran the stock 30 amp generator and Halogen headlights for years with no problems and many all night highway runs, it's all about setting things up right to begin with. These trucks did not ship from the factory with dim, yellow headlights. I installed a headlight relay harness and it did make an improvement, the more voltage to the headlights the better. It seemed to mostly improve side lighting, it's noticeably better and they don't dim at idle RPM anymore.

 

I will do the voltage drop test. The conundrum is that my lights are really nice and bright. Also, I can barrel down the highway as long as I want with the brights on, and they are perfect, but when I slow down, they will begin to flicker in a few minutes. There is ZERO dimming at idle.

 

Huh. Might be interesting to plug a voltmeter into the cigar lighter socket and see what's what when lights start to flicker.

 

Has anyone had great success with this particular kit on eBay?

 

I bought the $12 (delivered) el-cheapo eBay specials just to see how well they worked. I suppose you're talking about the whole harness. Quality is OK for the price although using genuine Bosch relays is probably a better plan. May need to get a little creative with the wiring depending where the battery is installed on a particular class of truck but for the money involved can't really complain.

In the video above the headlight brightness looks good, it's almost certainly a roasted headlight breaker integral to the switch. Can't really anything else because there isn't anything left.

What I found is, while the relay harness is a good upgrade, by itself it is otherwise only a patch or workaround of a system of weak or neglected grounds and connections. If headlights are yellow or dim or a new switch is flickering you can bet the rest of the ignition, starting circuit and accessories are current starved too.

Dim or yellow headlights is a pretty good diagnostic actually if you think about it. It ALWAYS means something is defective in the charging system, grounding or wiring and is definitely worth fixing.

 

The problem I have is once I plug in the right light, it will start to flicker. With it unplugged the left light is white bright.

 

What's voltage look like at the plug? An alternator/regulator going bad can start to chop 12 volts into something closer to ac and make lights wag like on a Harley...

 

Ok, I am going to replace the switch. The flickering was dangerously bad today. One more thing, could mismatched headlights cause an issue? The voltage regulator and alternator are original and likely need replacing too.

 

Flickering lights can be caused by the alternator regulator going bad. I usually see that in customer cars at idle though, and all the lights pulse including the dome light. Just because I say usually though doesn't mean it is a hard rule. An alternator can produce the correct voltage but not the amperage to charge. Voltage test the whole headlight circuit one connection at a time while the lights are flickering as well as your battery voltage.

When you say mismatched headlights do you mean brand name or type. Original incandescents are dim, halogens are brighter, H4 conversions need the relay harness, and Trucklite/Rigid has put out a capacitor kit (listed for Jeeps) for their LED headlamps to stop a flicker issue that came up on them.

 

Disregard the mismatched headlights comment. They do match as it turns out. At idle, the battery shows 13.5 volts, as do the headlight sockets. The four posts on the voltage regulator read from top to bottom, as follows: 14.35V, 14.54V, 7.36V, and 8.75V. The truck idled for 20 minutes with no flickering and the switch was barely warm. I will go for a drive and see if I can get flickering then.

 

Have you solved the issue?

Has anyone did the upgraded headlights with HIDS? Im considering this route as i will be replacing the Headlight Harness, Relay, Dimmer switch, alternator regulator.

 

I changed the switch and it has been perfect so far. I also recently replaced the voltage regulator. I will let you guys know if anything goes wrong.