H4 Headlamps & Relays

[Tidybuoy]

A new "unusual" problem developed over the weekend:

I recently installed new H4 headlamps & everything seemed to be working fine. I purchased a high power relay - but I haven't installed it yet.

This weekend, I installed a conversion kit for my Euro front turn signals (2 bulbs instead of one). When I got them all hooked up, the driver side flashed one bulb - then the other (seemed neat). When I got the passenger side done, both bulbs flashed at the same time.

My first thought was that this was some kind of German thing (just like the left/right parking lamps). But after a short while of admiring my new setup, I blew a fuse.

Reviewing various wiring diagrams revealed that the ground wire was hooked up to the wrong connection on the turnsignal bucket. But, this is how it had always been because I didn't touch that wire. I corrected & the blinkers started working correctly (both bulbs blinking at the same time).

THE PROBLEM:

Went for a drive last night & now both high & low beams are on. and when I switch back & forth, the dash light stays on for both low & high. The lights get a little dimmer on lows but definately not normal low. Also, when I got a few blocks from my house the headlights started flashing bright/dim/bright.

I went back home, looked at the stock headlight relay & when I wiggled the wires, everything fixed itself. WHAT HAPPENED HERE? By the way, the headlight flasher is relatively new.

THE QUESTION(S):

1) What is the difference between a relay & a fuse and why do I need to add a high-power relay for the H4's.

2) Based on previous posts, I'm told to add a high power relay. Does this replace the existing relay or is it a pure add.

3) Is it possible that the headlight wires are wrong & when I fixed the turn signal wiring, suddenly the headlight error revealed itself.

Any Help would be greatly appreciated! Thanks, in advance.

Vern

[Dave at Pelican Parts]

1) A fuse is a component that will destroy itself when too much current goes through it. They are rated for the maximum amount of current that they will allow--e.g., most of the 914 fuses are 8 Amp, which means if something tries to suck 9A through one the metal part of the fuse will fail and it will no longer conduct electricity.

A relay is an electrically-operated switch. Usually a heavy-duty switch. You run a large power wire (through a fuse!) to the input of the switch, then run another large wire from the output of the switch to whatever you are "feeding". You use two other wires to flip that switch on and off.

2) The "power relay" is used in addition to the stock relay. The stocker just directs power to either the high beams or the low beams. The power relay is intended to use the high-beam signal from the stock relay as one of its "switching" wires, while acting as a heavy-duty switch between a thick wire from the battery and the high-beam element of the headlight.

3) It is most likely, IMHO, that you have a poor ground connection. Check near the headlight buckets and also up under the dash. I'm thinking that when you wiggled the wires doing the change-over, you got the poor ground in better contact so it conducts well enough.

--DD

[Tidybuoy]

Perfect Answer! Thanks.

When I wiggled the stock relay, I also noticed that it had come un-clipped from the fuse box which may have contributed to the problem.

In a previous message, you stated that the most difficult part of adding the new power relay was running direct power from the battery, through the tunnel, to the forn trunk.

Fortunately, I did this a long time ago when I wired for a power amp. (using very heavy wire - almost like battery cable). I will probably just tap into this source and get this project done tonight.

Thanks Dave.

[Tidybuoy]

One more thing,

Any advice on what size fuse I shoud use for the H4's? This would be for the "in-line' fuse.

[Dave at Pelican Parts]

Figure a "nominal" voltage of 14.5V. Divide the power rating of the high-beams by that. If you got the 100W ones, for instance, each bulb would suck (100/14.5) 6.9A. That's just under 14 amps for both, but they will likely require more current than that when they start up.

I'd guess at a 20A fuse. But if you've already run a big cable from the battery, it should already be fused on that cable near the battery, right?? Right?

--DD

[Tidybuoy]

Yep, it's fused! Saved me a little more money.

Thanks!

[SteveStromberg]

Put the Hi Amp Relay cause you will be buying a Headlight relay running the amperage those 100watter 's use. I would use the Optilux 55-60 Super White as there are very bright but the same draw as stock bulbs. Steve

[SteveStromberg]

How about this Light, It has a driving light in it .


Steve