Hi, I added a low range headlight harness to add mor juice to my headlights. Before the harness High an Low Beams works fine. After, only Low Beams (although the harness does make them much bighter). I removed the harness and both work again like normal.

Any ideas what is interfering with the High Beams?

Here is the harness:
http://www.lowrangeoffroad.com/h4-he...iy-h4hlrh.html

I’m awaiting a reply from them now too. Pics of the unit and my install on one side attached. I’ve confirmed power and both grounds are working fine.

 

Are both fuses good? Inspect and probe them.
Got a multi-meter, correct?
I believe that harness has one relay to power the low and another to power the high beam.
When you switch to low and then to high beam, do you hear/feel/see the relays click?
Try swapping the relays and see if problem follows one relay.






This^^^ is not an ideal ground point. Use the one on the fender, Exactly where the negative battery cable grounds to the inner fender.

Unscrew grounding screw, sand paint off until you expose bare, shiny metal, clean old and new ring terminals to bare, shiny metal, apply thin coat of 100% silicone dielectric grease to fender, and ring terminals, re-install stock ground cable and ring terminal from H4 harness, Tighten screw well.

 

I spoke with Low Range Offroad and they refunded my harness. Evidently they crossed the "black and blue wires on your harness" and said "the black one shoudl be ground I think, not the blue one". He thinks I can swap them and it might fix the problem.

I'll also check the fuses and relays by swapping one.

The ground above is on the Drivers side fender. The Passenger side fender is grounded to where the negative is for the battery. I tried a lower ground and it wouldn't work so I defaulted to the above for now.

 

run both grounds back to the battery if you have to, at least as a test.

 

One reason Low Range Off Road is one of my go to places for parts. I have had great service from them buying stuff for my 4Runner. If something has been screwed up they have fixed it right away just like in your case.
Curious to see if swapping wires will work

 

I had the same problem when I got that harness for my Tacoma. I had to pop the spade terminals and redo it correctly, but my harness was wired for H4.

 

Also from Low-Range Offroad? Yet they have not fixed it on later products?

 

Tell me again what spade terminals you changed and where (at the bulb, relay, etc)?

 

You really need to either have instructions from Low-Range Offroad, OR have a schematic, OR carefully trace wiring before switching pins, as one kit may have different wiring or wire colors from the other.

 

It was from Low-Range but it wasn't their fault. I switched the terminals on my stock harness for H4 bulbs and forgot to switch them back for the new harness. Then instead of rewiring my stock harness back to 4656 I just corrected the new harness to match. It's a quick fix if you know how to wire relays and know the proper diagram for H4.

 

Update: I tried swapping wires, trying combinations of wires, but nothing simple worked. I think there is an issue with the wiring at the relays - and figuring it out isn’t worth the slight increase in light output. So I got my refund, pulled the harness off, and went back to OEM and back to normal.

 

Bummer, hopefully Low-Range figures the problem out
Or else I'll assemble one with pride in U.S.A. for my Yota brethren.
The H4 conversion harness is actually an essential modification for 2 reasons:
1) It will relieve your dimmer combo switch contacts of high current that could shorten their life (same wiring system flaw that Toyota made in the cranking system), and
2) Eliminate the power losses in the "convoluted path" over long wires, and dimmer switch contacts. 4Crawler explains this on his website.