thought this be kinda of cool to see how much power your getting to your head lights .... ive upgraded the ground wires to 4ga to the frame engine and fender im getting 12.50 volts engine off and about 13.46 volts at idle guess i dont need a harness ?

 

If that is measured at the back of the headlight connector under load, that is pretty good. You want to be within 0.5 volts of the battery voltage with the headlights on for optimum light output:
- http://www.4crawler.com/4x4/CheapTri...ml#VoltageTest

 

no thats just unplugged also the high beams are burned out so ill have to wait for new bulbs then try it again

 

Under no load any wiring will read good voltage. Voltage (drop) is equal to current time resistance (V = I x R). At no load, current is zero, so zero amps times any resistance (less than infinite) is zero, so you'll just be reading the battery voltage. The real test is to measure the voltage under load off the back of the headlight connector with the connector plugged in and the lights on:

 

ill dig around 2morrow im sure i got a good headlight bulb somewhere

 

Mine's the same as battery voltage. I run relays for the headlights though. Even 1 volt increase makes a BIG difference in light output.

 

looks about 12.86 volts at idle hmm maybe i should make a harness since i cant see paying about 50 bucks for one

 

ok i priced out parts to make a harness looks to be about $30 bucks looks like im gonna make one

 

im getting about 85-100v to my headlight bulbs

 

Glad to see this at the top; I'm starting to do some "fiddling around" on my 4Runner & was just thinking about the headlight harness upgrade & testing the voltage to the headlights. I'm glad 4Crawler spelled out the proper procedure because there are three things I suck buttermilk at doing - rebuilding automatic transmissions, knowing what tire/wheel combo will work & nearly anything electrical. I can test for voltage & that's about it.

Anyone know where to get that upgraded harness? I used to have a link saved in my favorites but it's gone now....was it trailgear?

 

See below:
- http://www.4crawler.com/4x4/CheapTri...OnLineOrdering

 

i haven't tested mine

 

LOL...thanks!

 

My headlight plugs don't lend themselves to testing while plugged into the light; I COULD strip a section but I don't like doing that or disassemble the plugh but I'm not crazy about that idea either.

I tested the voltage with the lights on high beam, engine not running through the drivers side plug (off the light) but with the passenger side on the light so there was some load, one terminal tested about a half a volt lower than the battery & the other was a full one volt lower (1 ground - 2 hot).

I suppose that from what I read on 4Crwalers site the test is worthless because they weren't both plugged in?

 

That is a partial test. You are measuring the system voltage drop from the load of one light, at least in the part of the circuit that is common to both lights. Rough rule of thumb is that you would see about twice that voltage drop if both lights were connected. You can also try sliding the connector back off the bulb until you can just see the bulb contacts and use a volt meter probe on the exposed contacts.

 

Thanks for the free info, very helpful. I'm an infant when it comes to electrical stuff & my dad is (was) a whiz before his mind started to go South on him. I always just relied on him over the years....an obvious mistake; I should've learned all I could.

As far as sliding the connector back, I looked at that possibility & the way it is on my '95 there just doesn't seem to be any way. Unless I take the bulb out of the housing? That thought just came to me; I'll try that & see if I can access the terminals like that.

Thanks again 4Crawler; I'll be ordering that harness if this test shows I need it.

 

You probably have the 9004 lamps. They can be harder to probe as the connector shell is more enclosed than the H4:



Some of the shells have a back flap that can be opened up to access the internals, but others are sealed up. Might also be able to use two pieces of small gauge wire that can slip into the socket and still allow the socket to plug in. But your test with one lamp plugged in is still a decent test. You can also see if you can tell any light output difference with one and two lamps plugged in. That is does the first lamp dim a little when the 2nd one is plugged in.

 

Yeah I have the 9004 type & it appeared sealed; I thought about putting some wire in there but I didn't want to short anything out. I got busy trying to Jerry rig my wifes vacuum cleaner for a while today so I'll have to check the 4Runner out tomorrow.