Relayed the headlights - now the ARC light is flashing

[GTVeloce]

So I finally got around to putting relays on the 75 close to the headlights and hallelujah, the lights are much better.

However, now, when I switch my headlights are on, the corresponding ARC light flicks on and off. It was working fine before the mod and my ARC has always worked perfectly so I'm guessing it is because the ARC works on a certain load on a system and I have effectively removed a big chuck of the load so it is thinking 'ah, he must be down a headlight. I'll let him know.'

I'm thinking a resister between the original headlight wire (which is still attached) and earth should fix the problem but I don't know what value to use. Does any electrical boffins know or anybody fixed the same problem? Too little and it won't work. Too much and it may reduce the brightness of the rest of the system.

[Divano Veloce]

Hi Julian, I don't know how much current the arc wants to see but once this is determined the resistor value is easily calculated using ohms law v=ir. Once you've selected a value for the resistor then you need to calculate how much power it will dissipate using p=iv. Select a resistor with a rating of about 2 times, maybe one with its own heat sink. Some hid kits come with such resistors so maybe see value/rating resistor they use

[Cool Jesus]

Hey GT, excuse my ignorance here, haven't been inside a 75 yet. Can you describe the symbol that is flashing or post a pic of it? Reason I ask is that I don't see how a relay will cause this fault and I'm having difficulty locating an image of where or what the headlight out warning is for the 75 arc system.

[Cool Jesus]

Never mind found an image. So which warning is blinking?
Also found that the ARC works by sampling the continuity or lack of in the various circuits being monitored. So lamp circuit is sampled through a current resistor and the current is compared to a nominal value any departure from this value will cause the alarm to flash. Now is the relay wired so that the old wiring goes through pins 85-86 and you have direct 12v to the globe via pins 30-87? If this is so, again ignorance warning here  , if the globe blows the ARC wont pick this up anyway (unless there's a specific way around this).

[Cool Jesus]

Oh and while I was surfing I came a cross a thread for fixing the ARC from ghost blinking.

http://www.alfabb.com/bb/forums/milano-75-1985-1993/69476-real-fix-arc-blinking-lights.html

Would measuring the resistance of the globe give the required value, or is that too simple?

[GTVeloce]

CJ; yes, that's the ARC and the light in question is the bottom left. As you discovered, it works by comparing continuity against a nominal value. I have wired my relay by using the existing feed to the globe to provide energy to the coil (86) with power (30) coming direct off the battery and then (87) feeding the new headlight socket. This means if I blow a globe my ARC warning light will not notice it and let me know but I prefer to have bright headlights and just keep an eye on the bulbs.

DV; I will dig up some rusty ohm's law memory and get calculating.

Select a resistor with a rating of about 2 times

2 times of what?

Good thinking of using a heat sink.

Thanks guys

[Divano Veloce]

power rating. so 10w resistor if you calculate 5 watts through the required resistance.

link below brings up images of ceramic and heatsink resistors. THey get hot and will melt plastic if not mounted properly so best to use a heatsink type and mount it to sheetmetal somewhere

http://www.google.com.au/images?hl=en-AU&q=10w+resistor&gbv=2&sa=X&oi=image_result_group&ei=JUVUVKLfD9jz8gXjo4CADg&ved=0CDIQsAQ

[Cool Jesus]

Again, not offay with the 75, but I've found that warning related to the side lights? The extra current released by the relay setup, hasn't gone and blown an old set of parkers or the rear fog has it? Does that warnings also include the main beam? I'm only going off this web page
http://www.users.on.net/~craigf/arc.htm which describes that warning as the parking lights and rear fog light?

[shiny_car]

Again, not offay with the 75, but I've found that warning related to the side lights?

^^^ Yep, that warning relates to the side/parking lights and rear foglight, not the headlights.

Obviously, check if one of those is blown. 

[GTVeloce]

Ok, people are correct, the light doesn't check the headlights, only the park lights and fog lights. However, all of my lights work fine. Fogs and all. Light only comes on with the lights turned on and it comes and goes.

Maybe one or some of the connectors are poor. Good enough for the light to work still but still drawing too much current. They all seem perfectly bright... And I still don't know why it only started after I installed the relays on the headlights.

[Cool Jesus]

I think your on the right path. It does seem too coincidental that it started after the relay install. My initial thoughts are that by adding the relays, you free up (or reduce) current draw in the lighting circuit. How old are the side/parking lights? Have no idea of where or what globes re used as your parkers (assuming there's no side lights). The parkers are always on with any headlight use, if there not expensive, try a good set of replacement globes. Is the warning occurring when stationary or in motion? If in motion, I'd think that the globe may be on the way out and element is teatering on failure.

An alternative is that the ARC could be playing up per the thread I mentioned above and it's a totally Alfa coincidence that it's occurred now Or as your suggesting a connection somewhere I loose. Could be at the globe end or even at the light switch. Just curious, does the 75 also suffer from too much current through the light switch, hence the modification? I ask as I'm not finding any threads that mention this since trying to help out here. There's plenty of threads for the alfettas, but they are older.

[shiny_car]

I don't think the error should be happening, so...how are these relays wired up? Presumably they are standard SPST (single pole single throw) relays? Thus 4 connections (or 5, if it is has two 87 outputs):

85: usually the trigger for the relay
86: usually the ground for the relay
30: usually the power supply
87: usually the power output to the headlights

So what wires are connected to each terminal? Photos?

From checking the wiring schematics, the error shouldn't happen, because the headlights and parkers run off different circuits. Thus, makes me wonder if things are wired incorrectly.

Of course, Alfas being Alfas, it could be wired correctly, and still cause the error! But...only in your car too and in no-one else's. 

[GTVeloce]

Yes, I think I have connected them correctly.
85: Feed from the original headlight plug
86: Earth
30: +12V
87: output to new left headlight plug
87: output to new right headlight plug

Then the same again but for high beam. This means the original plugs are still there with one of them being used for feeds and the other not used at all.

It also meant if I ever wanted to I could revert back to original wiring and plugs very easily. Which has me thinking, why don't I do just that and see if the warning lamp is still there?!

The front park lamps are not connected via the main plug - they have their own wiring and plug.

[shiny_car]

Indeed, wiring sounds fine.

Yes, I was going to suggest if it's easy, to revert to the direct, non-relay, wiring and see if the warning light goes off.

I presume you haven't changed any of the parking light globes to LED?

[GTVeloce]

Fixed it! By chance, I had to remove one of the headlights to straighten some bodywork when an errant truck decided to reverse into us in India. While it was out I took the chance to clean all the connecters (plugs) in that area including the park light plug. Just removed the male connections from the plug with a small flat screwdriver and sanded them till shiny followed by a squirt of contact cleaner. The female plugs just got the cleaner.

Since then the ARC light has never returned. Somehow the poor connection was enough to trip the ARC but not bad enough to kill the light.