H4 Upgrade
 

I've installed relays on my low and high beam circuits. Can I safely use 80/100 H4 bulbs? I know the relays protect the swich but I'm concerned about the factory wiring.

Thanks in advance,

Robo

Good question. I think the gauge of the factory headlight wiring is large enough, but your connections need to be clean and sound. This especially includes the grounds.

On my '72 restoration, I've installed relays, and 10 awg wiring directly from the battery to the bulbs (via the relays). The factory harness has been completely bypassed. I've got 100W bulbs but am looking for something higher. At this point the only thing I'm worried about is melting the glass of my lenses :D

With good relays and proper 10g wiring, grounds, etc, one can run 100/150 H4 bulbs......:)

I thought I read you have to replace the connectors with something different to handle over a 80/100.

If not, I want bigger bulbs.

My experience using 80w/100w bulbs was that the plastic plug or bulb holder melted with the high heat generated by the higher wattage.Something to be aware of.

Wire is typically 'rated' by size & the current (amperage) that it can safely carry. 14 AWG (American Wire Gauge) can safely carry 15 Amperes. 12 AWG for 20 amp. 10 AWG for 30 amp.

Using a derivative of Ohm's law: P (power in wattage) = E (voltage in volts) X I (current in amps), simply add up the total wattage (high + low) & divide by the voltage (12). For 80/100 that would be 180w/12v=15 amps.

You would need 14 AWG wire at a minimum. But as above, the plastic connectors might melt so the Bakelite HD versions are a wise choice.

Ian

What is the factory wire gauge? I am going to do a H4 conversion over the winter and will replace the wiring to the lamps anyway. Most of the OEM stuff looks to be 16 gauge.
Where are the higher amperage/heat Bakelite connectors available? I searched Pelican and couldn't find them.

I also believe that the factory wire is 16 AWG but that was just from visible inspection. I know that mine had stock bulbs & the wire was hardened & blackened (from mild overheating) for about 2 inches from the connector. I rewired the main lghts with 12 gauge & re-used the parking & signal light wires. I also ran a new 18 gauge wire for the city light to use as an always-on driving light to ward off soccermoms in SUVs.

The HD Bakelite sockets are made by Hella & they are available from Daniel Stern Lighting & not from our host.

http://members.rennlist.com/imcarthur/hellasocket.jpg

Ian

Good stuff!

I just did an H4 conversion on my '87 and will be building a stand-alone 12ga. harness using ceramic HD H4 plugs I sourced from Daniel Stern Lighting. He is a wealth of knowledge regarding lighting.

just my routine


I ran 130/100w Narva for years. They burnt out after 5-15k night miles.

I currently use Osram 85/80w, pn 64206, as a replacement and can't tell the difference comparing one Osram 85/80w hooked up to one side and the Narva 130/100w on the other. The Osram is a beefer bulb if you compare them.


if you run big big watt bulbs don't lean on the flasher as it engages both high and low beam at the same time. The bulb ground will melt.

I also use E-code lens' as the DOT US headlight lens sucks.

I haven't read anyone having any trouble with the relays' contacts toasting that pelican or Marcos sells.

remember - if you install relays - like you SHOULD - then the wire run is quite short. Thus, the total resistance is low. I have never bothered to replace the stock wiring. BUT, I cleaned up all ground points and connectors in that area. That is a huge source of resistance -- it is called contact resistance.

The std. recommendations are based on much longer runs of wire than we deal with here.


I have not had a heat or melting issue with the stock bulb sockets on two cars running high output bulbs in H4's and H1's. BUT I clean the sockets and use a conductive paste or dielectric grease.

I got some fairly trick ceramic sockets from Dan Stern. Good tip on the dielectric grease.

When I bought my '87 it had 80/100w bulbs installed in the oem H5's. The driver's side light was acting a bit funny and when I removed it to inspect the problem the oem socket had partially melted, so it definitely does happen. I like the dielectric grease idea too, I will have to do that with my H4's.

going thru this myself...thanks for the input fellas