Koito H4 kits CHEAP!!!!!

[John76]

3 hours ago, popovm said:

even the 76’s factory wiring was a little sketchy!

Sketchy is a good word!

I try to avoid high current loads from flowing through the ignition and headlight switches. Even the turn signal/high beam flasher is a bit sketchy. 

Yes, it would be a good idea to use the relays/fuses included in the Toyota light kit. 

I have yet to install my Koito H4s but will share a sketch of how I plugged everything in when I get a chance.

Stay tuned,

John

[visionaut]

lol - I guess I’m sketchy then. I’ve been running similar power H4s since 2001 on the factory wiring. When I installed them, my review showed beefier wiring  already in place for the headlights, plus dual relays, and I trusted the BMW engineers used  a robust enough factor of safety - the H4s were/are only 15W more than stock. 
 

What failures, damage or problems should I be seeing from 20+ years of sketching? Nothing has overheated, melted, worn out…

 

The BMW engineers could have easily wired the headlight relays direct to the battery  (or just the high beam circuit when they added the third relay) - why didn’t they? Couldn’t they have wired fuse 11 like fuse 1-2 with direct battery power?

 

Sketchy Tom.

[roadhog0]

4 hours ago, popovm said:

So in other words, it would be a good idea to use the harness that comes with this kit that goes direct to the battery? I was going to skip that assuming that the relays in the 76 meant direct to battery but sounds like that is not true at all and that even the 76’s factory wiring was a little sketchy!

If you're worried about it on a late car I would just use all the factory wiring, but pull power direct from battery for the relays (dont forget to add a fuse). That would make for an easier job, and should net the same results. But I've had no bad luck with the factory BMW wiring. Could get a voltmeter out and check for voltage drop across the system..... 🤔

[m42002]

21 hours ago, John76 said:

The '76ers have three relays (High beam, Low Bean and Horn), and none are powered directly from the battery. 

We love your diagrams, John! Makes everything so much easier to read. Thanks.

 

So basically, if I run a fused power from (both) relay pin #30 to the battery, I will have to turn off my own headlights?!?

Any other downsides to doing this? 

Edited August 21 by m42002

[Son of Marty]

1 hour ago, roadhog0 said:

f you're worried about it on a late car I would just use all the factory wiring, but pull power direct from battery for the relays (dont forget to add a fuse). That would make for an easier job, and should net the same results. But I've had no bad luck with the factory BMW wiring. Could get a voltmeter out and check for voltage drop across the system..... 🤔

THIS.

[torquewrench80]

The factory never anticipated owners using 80/100 watt halogen bulbs that would melt the dip switch when used. Don't ask me how I know that. 

[2002iii]

3 hours ago, torquewrench80 said:

The factory never anticipated owners using 80/100 watt halogen bulbs that would melt the dip switch when used. Don't ask me how I know that. 

Reminds me of the time I let the smoke out of the ignition switch on a 1600 that was pulled out of a barn after a couple decades. Bakelite plastic melting puts off some noxious fumes and one of the nastiest smells I have ever smelt!!!!!!

[visionaut]

9 hours ago, torquewrench80 said:

The factory never anticipated owners using 80/100 watt halogen bulbs that would melt the dip switch when used. Don't ask me how I know that. 

No one suggested running 100 watts on the factory wiring..

 

These are 55/60W. The sealed beams were 40/45W. BMW obviously felt they had a solid design, they even added an extra connector in the front bulkhead running off of Fuse 11 to ADD MORE LIGHTS onto to the same circuit…

 

[John76]

1 hour ago, visionaut said:

they even added an extra connector in the front bulkhead running off of Fuse 11 to ADD MORE LIGHTS

Tom, 

That extra connector in the wiring harness near the battery is used as a relay trigger source for driving lights.

This connects to tab #86 on the relay. Tab #30 connects directly to the battery + through a separate fuse, #87 tab goes to the driving lights, and tab #85 is grounded through a switch on the dash.

 

[visionaut]

32 minutes ago, John76 said:

Tom, 

That extra connector in the wiring harness near the battery is used as a relay trigger source for driving lights.

This connects to tab #86 on the relay. Tab #30 connects directly to the battery + through a separate fuse, #87 tab goes to the driving lights, and tab #85 is grounded through a switch on the dash.

 

John, there are 2 connectors up front - one for Foglights and the other for Additional Lamps. One has upsized wires to 2.5mm vs the other with the normal .75mm size. Only the .75mm connector is identified as being for the Fog Lamp relay…

 

The 2.5mm wired connector is the one off Fuse 11. The .75mm Fog Light relay connector comes off Fuse 8.

 

My point that BMW expected additional lighting loads on the factory wiring holds..

[John76]

1 hour ago, visionaut said:

My point that BMW expected additional lighting loads on the factory wiring holds..

The 2.5mm high beam wires are needed because only one 16A fuse (#11) protects two 60W bulbs. Adding two more driving lights @ 60W each without a separate relay directly connected to the battery would surely cause a problem with the factory wiring and switches. Yes, BMW made this provision for adding more lights...but only if done through dedicated relays and fuses.

The .75mm wires to the parking/headlight tap are much too small for adding two halogen 55W fog lights, since they would both be powered by one 8A fuse (#9 or #10). That tap should also be used as low-amp trigger to a separate relay and fuse.

 

 

 

 

[visionaut]

Wiring and capacity geekness…

 

Amps for 40/45 = 45W/12V=3.75A (2 lamps @ 7.5A)

Amps for 55/60 = 60W/12V=5A (2 lamps @ 10A)

 

NEC rule says only 80% capacity, so use 1.25 factor;  (BMW exceeds NEC…)

 

Amps for pair of 40/45 = 9.4A

Amps for pair of 55/60 = 12.5A

 

—

 

.75mm2 cross-section wire = .98mm core diameter = 19 AWG

2.5mm2 cross-section wire = 1.78mm core diameter = 13 AWG

 

AWG 19 is rated for 13A

AWG 13 is rated for 24A.

So 2.5mm2 is good to go for headlight power handling.

And the 3.5A unused capacity on the 16A Fuse 11  (assuming H4s) is good for powering only a pair of 20W ‘Additional Lamps’.

 

—- you can add relays, it’s likely better if you can get that all working at the ignition/headlight switches, but I’m sticking with simple, calculates okay, and what’s worked trouble free for 20+ years. 😋

Sketchy Tom

 

[2002iii]

52 minutes ago, visionaut said:

Wiring and capacity geekness…

 

Amps for 40/45 = 45W/12V=3.75A (2 lamps @ 7.5A)

Amps for 55/60 = 60W/12V=5A (2 lamps @ 10A)

 

NEC rule says only 80% capacity, so use 1.25 factor;  (BMW exceeds NEC…)

 

Amps for pair of 40/45 = 9.4A

Amps for pair of 55/60 = 12.5A

 

—

 

.75mm2 cross-section wire = .98mm core diameter = 19 AWG

2.5mm2 cross-section wire = 1.78mm core diameter = 13 AWG

 

AWG 19 is rated for 13A

AWG 13 is rated for 24A.

So 2.5mm2 is good to go for headlight power handling.

And the 3.5A unused capacity on the 16A Fuse 11  (assuming H4s) is good for powering only a pair of 20W ‘Additional Lamps’.

 

—- you can add relays, it’s likely better if you can get that all working at the ignition/headlight switches, but I’m sticking with simple, calculates okay, and what’s worked trouble free for 20+ years. 😋

Sketchy Tom

 

I'm having flashbacks of electrical class. 

 

V=I+R

[John76]

2 minutes ago, 2002iii said:

I'm having flashbacks of electrical class. 

I'm in totally in the dark. 

[Son of Marty]

36 minutes ago, John76 said:

I'm in totally in the dark. 

That's what happens when you use Lucas relay's😆.