Intermittent headlight failure

[NathanR]

I Installed H4 headlights and a relay kit in my 911 about 6 years ago. I've been using 80/100w bulbs. Last winter I had a couple instances when I went to drive to work in the morning and no headlights. Luckily I have a backup car. Upon inspection the lights worked fine. I replaced the headlight bulbs just to rule them out.

This morning, same failure. When I got home I was able to pull the switch a few times with still no lights, but I could hear the relays click. I tried the high beams, The high beams worked. Then the low beams worked.

Installed separate fuses on the power feed to the relay and they seem fine

All the wiring looks as new as the day I installed it. Haven't pulled the headlights yet.

Could it be the relays? What else can I check?

[wildturkey]

Earth points.

When you installed the headlight relays did you run a new earth?

I think the factory earths are located just in front of the battery.

[NathanR]

Yes, the headlight grounds are new wires to the front bulkhead ground that the battery negative also uses (through a cutoff switch). I checked this visually while I was poking around in there. There area bunch of wires there, and the headlight grounds seemed secure.

I ran a ground for the relay but don't remember where I connected it. I will check it

[NathanR]

Relays are grounded to ground point by front left shock mounting point. New wires. I checked them with a meter, and their fine, now. Of course the headlights are working too.

[targa80]

If your wiring has checked out and you replaced the bulbs then it sounds like you have a relay that is acting intermittently.

[wildturkey]

I guess you have done the push and shove test. With the headlights on wriggle and knock all the looms / relays within that area.

[porwolf]

I would use a volt meter and trace all wires and sockets including ground wires and ground connections. 80/100W are quite a load on the circuit, wires and connectors including the light bulb socket. The car was not designed for that load. It could be a heat corrosion problem somewhere in the circuits.

[timmy2]

About a year after replacing my headlights Hi/Lo turn signal stalk switch and installing the relay kit I had similar problems, then the headlights started to bounce into high beam on their own. Turned out I needed to adjust the contacts in the new hi/lo switch even with the relay kit.



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[wwest]

To much wattage, HEAT, for the bulb connecting sockets.

[porwolf]

Originally Posted by timmy2

About a year after replacing my headlights Hi/Lo turn signal stalk switch and installing the relay kit I had similar problems, then the headlights started to bounce into high beam on their own. Turned out I needed to adjust the contacts in the new hi/lo switch even with the relay kit.



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The relays only protect the electrical contacts inside the turn signal/headlight-dimmer switch. The issue with turning on high beams arbitrarily has to do with the bending of a small, non-electrical, metal plate inside the stalk:

[HawgRyder]

Universal relays are cheap...buy some spares.
The points inside them are a "useable" item...they only have just so many operations in them...when they go intermittant they are done.
Or....why not try solid state relays?
They are available in 12V activation types...and the pass through current can be hundreds of Amps
(for powering the lights).
Some are rated in millions of cycles.
Bob

[NathanR]

I fixed my hi/lo switch a couple years ago (thanks to my fellow Pelicans for that clue) and it works flawlessly. I repaired the original switch, didn't replace.

Porwolf, wwest, the circuit path for the pwer to the bulbs is all new, heavy gauge stuff. Except maybe the inside of the relays. The bulb sockets are ceramic blocks. The wire is 8 or 10 gauge.

I like Bob's suggestion and am going to try that next. I'm also going pull apart the two grounds just to check for corrosion (though I don't expect it). Do you guys ever put grease on electrical connections to prevent corrosion? Vaseline?

Thanks all
N/

[porwolf]

NathanR, did you install 2 or 4 relays? Normally people only install 2 relays, one for both low beams and the other for the high beams. Then failure of one relay could cause failure of both headlights. But if your problem affects high and low beams at the same time maybe the main headlight switch is to blame. Could be occasional internal contact failure there.

[Lmarche]

Hi, Two weeks ago, I was trying to adjust the gage's dimmer during a nite driving, and wow headlights turned off, it only did it once, but maybe it worth checking the switch. Good luck.

[NathanR]

One relay for hi, one for low.
By the time I thought to check the hi beams, they worked. So maybe it's just the lo beam relay. I rarely use the highs, they are so damn bright. When I do, reflections off street signs hurt my eyes...
I wonder if the kit came with four, because I remember having some boxes that size with my car electrical leftover bits.... I recently moved and had to go through all that stuff.
Good suggestion, thanks

[NathanR]

Lmarche, mine does the same thing, and the switch was my first assumption. But when I heard the relays clicking with no lights, I figured it couldn't be the switch at that point since the switch provides the input signal to the relay.

Or maybe both are intermittent. I'll replace the relay tomorrow and drive it like it's fixed. It will work fine for months even if it's not.

[NathanR]

Ok. I did the following over the weekend:

Changed both headlight fuses
Swapped hi and low relays, and bought a spare
Disassembled both relay and headlight ground points and wire brushed before reassembly

Hopefully this takes care of it. If the hi beams occasionally don't work, I'll know it was the relay.