I was reading this thread and it was mentioned that the stock wiring cannot support four 55w bulbs.
I will be replacing my headlights with Optix 2020s


https://www.fiero.nl/forum/A...060811-2-068909.html

I don't think that info is correct. I've used 55 w and no problem

Arn

What about running all 4?

I haven't done it myself, but, I have done it with my 1972 Datsun 510 and it worked fine. The real problem with running all 4 is that if a cop comes by the other way at night, he's going to pull you over for a MV violation if you forget to dim. The only way to ensure you don't get a ticket is to have the high beams on a separate circuit with a separate switch.

Hope this helps.

Arn

quote Originally posted by Arns85GT: I haven't done it myself, but, I have done it with my 1972 Datsun 510 and it worked fine. The real problem with running all 4 is that if a cop comes by the other way at night, he's going to pull you over for a MV violation if you forget to dim. The only way to ensure you don't get a ticket is to have the high beams on a separate circuit with a separate switch. Hope this helps. Arn

No, that is what I was trying to say. I am going to hook them up like stock as far as high beam/low beam, but I was just wondering if the load of the 4 lights running at once will be a problem.

Since you have done it did the lights put out more than the stocks?

My lights were CB 100watt rally lights X 4 I ran them off two different fuses.

Essentially if you have 40w low beams X 2 + 55w high beams X 2 you will have 190 w output. Yes that is pretty bright. You can check the amperage requirement pretty easily to see if your fuse will handle it. If not, neither will your wires.

Arn

I'm planning on adding relays up front that will power the lights directly from the battery. I don't like how the Fiero headlights are actually powered through the switch. I know mine gets fairly warm when the lights are on for a while.

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Here's a thread you migt find useful

https://www.fiero.nl/forum/A...060811-2-068914.html

I asked the same question that you asked above in one of the projector headlight thrreads (i just can't find it). The conclusion was that the stock bulbs are 35 watts low beam and 55 watts high beam. If you wanna use (4) 55 watt lights at the same time, you are essentially doubling the load from the stock configuration. The stock high beams = 55 watts oer side, (2) 55 watt = 110 watts per side. The conlcusion was to use a relay to make sure you don't overload the system. In your case, you could just add a relay ofr the extra (2) 55 watt bulbs, so that the stock wiring is taking the 55 watt + relay voltage for each side.

Two things to be aware of:

1. If you overlaod your system, it might not blow a fuse right away, but slowly burn out if you keep your lights on for a long while. In other words, it might be OK for driving around town, but your lights may go out while you're taking a long trip.

2. There is a fusable link in the headlight circuit. So if you are experimenting and lose power, you might have blown a fuse AND your fusable link - check the link if you don't get power back after replacing the fuse.

PS. Xanth: a warm headlight switch is normal when the lights are on.

[This message has been edited by PaulJK (edited 10-04-2007).]

a long time ago I changed my headlights to the h4 style. I installed some 100 watt low x 120 watt high beam bulbs (purchased overseas). My headlight switch suddenly got really hot when the high beams were active. I converted the headlight to Bosche style relays that power the headlights from the battery directly. The headlight switch switched the relays on. one relay was for high beams, one for low beams.
I added a 20 amp fuse to the power feed from the battery (they needed 19). My switch is now cooler than before I put these 100 watt bulbs in.

I did something similar, got a deal on an H4 conversion harness from AR. Worked well since I had put one of V8 Archie's battery boxes up front. Light switch stays cooool.

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John DuRette
Custom 85 SE/86 GT
"Kinda makes you nostalgic for a Members Only jacket"

I'm not good with auto wiring except when it comes to audio. I am confuse on how to use two different fuses, but run the same switch. Running 100w low beams and the same high beams would be sweet, but how do I do this safely or just running 4x 55w safely (2high / 2low). (diagram please).

[This message has been edited by goatnipples2002 (edited 10-04-2007).]

Just to clear up some things. The stock headlights are 35W low beam and 55W high beam. I think the Sylvania Silverstar's are 45W/65W.
The wires to the lights are 12 gauge. So at 35W you are drawing about 3 amps and at 55W you are drawing about 4.5 amps per headlight. Each wire can handle about 9.5W. With both high and low beam on that is a total of around 7.5 amps. The wiring is fine. I cannot say how many amps the headlight switch can handle.

Basically you have about 8 amps per side that you can utilize. (or about 96 W per side) The guy who had the 120W high beams was drawing 10 amps thru the wire, hence that is why it heated up. Many here (myself included) have upgraded to the 90MM headlights which are 65W low with a projector beam and 65W high beam with a straight lens. (they use the H9 bulbs) I personally would not run the low and high beams on at the same time with them.

To answer the original question, running two 55W lights per side would be running about 9 amps per side which is right around the limit of the wire. Now add in the fact that the wiring and connectors are 20+ years old and the current limit of the switch is unknown, I would not run two 55W bulbs on one side.
You can however, hook a relay to the second pair of 55W bulbs and run your own 12 AWG wire from the battery. This would avoid drawing high current thru the stock wiring and thru the headlight switch.

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Oreif, too bad I've already given you a +. As always you are a fount of knowledge.

Arn

I just looked up the Fiero wiring diagrams. (1986 Factory Service Manual) Out of the headlight switch is a 10 AWG wire which goes to the low/high beam switch. Out of the low/high switch is two 12 AWG to each light, One is to each low beam and the other is to each high beam. The 10 AWG wire can handle about 15 amps max so I would assume the headlight switch would be rated the same. That would mean the absolute max would be 180W total for all headlights so four 55W would be a total of 220W.


NOTE: The wire "max" that I have posted in this post and my one above is the "recommended" safe max limit. The wires can take more, But then the wires would start to heat up. How much would depend on current levels and wire condition.

There's more to figuring wire size / current capacity than just the wire gauge - the length of the wire is also important.

Every piece of wire has resistance - as current flows through this resistance some of the electrical power is converted to heat. If you know the resistance / foot of the wire you're using, then multiply that by the number of feet in the run and use P=(I*I)R to determine the power (in watts) being lost in the wiring. If the wire is twice as long it has twice the resistance; this doesn't affect the safe current handling capacity, but it has a profound effect upon the amount of power lost in the wiring.

Safe current handling is based upon the wire staying cool enough that the insulation doesn't fail. But there's more to consider here. The power lost heating the wires is power that doesn't get to the headlight bulb - and those incandescent bulbs lose brightness rapidly as their terminal voltage drops. You could be losing 30% of the light output from your headlights and still be running the wiring safely.

Want to put a number on the power lost in your headlight wiring? Grab an accurate voltmeter and measure the voltage at the socket on the back of the headlight bulb with the engine running and the battery fully charged. Now measure the voltage at the battery terminals; subtract the headlight voltage from the battery voltage and multiply the result by the (roughly) 9 amps the headlights are drawing. That'll give you the number of watts that are being lost in the wiring.

And if you're measuring more than 1/2 volt of difference between those two measurements it'd be worth your time to track the problem down and correct it. Don't forget the grounds; they're part of the circuit, too.

If you're thinking of adding more or higher wattage bulbs to the headlight circuit, be sure and do these measurements first so you know what's going on. Do the measurements again after your new lamps are installed. You might find out that higher wattage lamps produce less usable light because of the increased losses in the wiring...

quote Originally posted by Whuffo: There's more to figuring wire size / current capacity than just the wire gauge - the length of the wire is also important. Every piece of wire has resistance - as current flows through this resistance some of the electrical power is converted to heat. If you know the resistance / foot of the wire you're using, then multiply that by the number of feet in the run and use P=(I*I)R to determine the power (in watts) being lost in the wiring. If the wire is twice as long it has twice the resistance; this doesn't affect the safe current handling capacity, but it has a profound effect upon the amount of power lost in the wiring. Safe current handling is based upon the wire staying cool enough that the insulation doesn't fail. But there's more to consider here. The power lost heating the wires is power that doesn't get to the headlight bulb - and those incandescent bulbs lose brightness rapidly as their terminal voltage drops. You could be losing 30% of the light output from your headlights and still be running the wiring safely. Want to put a number on the power lost in your headlight wiring? Grab an accurate voltmeter and measure the voltage at the socket on the back of the headlight bulb with the engine running and the battery fully charged. Now measure the voltage at the battery terminals; subtract the headlight voltage from the battery voltage and multiply the result by the (roughly) 9 amps the headlights are drawing. That'll give you the number of watts that are being lost in the wiring. And if you're measuring more than 1/2 volt of difference between those two measurements it'd be worth your time to track the problem down and correct it. Don't forget the grounds; they're part of the circuit, too. If you're thinking of adding more or higher wattage bulbs to the headlight circuit, be sure and do these measurements first so you know what's going on. Do the measurements again after your new lamps are installed. You might find out that higher wattage lamps produce less usable light because of the increased losses in the wiring...

While the above is correct, On a car it isn't going to have a large effect unless you exceed the safe current limits of the wire. (or have corroded wires/connectors) A 10 AWG stranded wire is typically .9989 ohms per 1000 ft or .0009 ohms per foot. A 12 AWG stranded wire is typically 1.588 ohms per 1000 ft or .0015 ohms per foot. On a car you are talking less than 25 ft max for any single wire.

I do agree that if you are going to add or change the lighting to more powerful lights, You should check out the wires and connector. Corrosion can increase resistance and 20 year old wires and connectors could easily have some.

[This message has been edited by Oreif (edited 10-05-2007).]

quote Originally posted by Oreif: While the above is correct, On a car it isn't going to have a large effect unless you exceed the safe current limits of the wire. (or have corroded wires/connectors) A 10 AWG stranded wire is typically .9989 ohms per 1000 ft or .0009 ohms per foot. A 12 AWG stranded wire is typically 1.588 ohms per 1000 ft or .0015 ohms per foot. On a car you are talking less than 25 ft max for any single wire. I do agree that if you are going to add or change the lighting to more powerful lights, You should check out the wires and connector. Corrosion can increase resistance and 20 year old wires and connectors could easily have some.

You might want to put the voltmeter to your car and see what you've got. The factory wiring is just barely big enough to handle the stock headlights - and after so many years the switches and connectors aren't all that good anymore. While the wire itself may be OK and still frairly low resistance, the entire circuit is what's important. Even on a stock Fiero - if you think the headlights are dim this would be a good place to start your diagnosis.

Practically speaking, I have never had a wire problem in any car except where they've been sprained or nicked. I have had, on the other hand, numerous connector problems. The connectors get corroded over time. The latest one was my trunk release connector. I thought it was the ground but after adding an additional ground wire I found out different. It was the connector.

Alot of dim headlights simple need their connections cleaned, both at the light and at the relay.

Arn

Sorry but (35w +35w +55w +55w = 180w total), to figure your amps using Ohms Law you have (W / V = I or amps) so 180 / 12 = 15 amps. To figure voltage drop you use (2 x K x D x I)/ Circular mils = Voltage drop, (approximate K = 12.9 for copper and 21.2 for aluminum) therefore (2 x 12.9 x 25' x 15) / 6530 Cmils = 1.48 volts lost in a 25 ft run using number 12 wire. For a number 10 wire you would loose .9 volts in 25 ft. Circular mils of wire can be found in any NEC Book (national electrical code) in table 8 in the back of the book. Take it from me on these specs I should know I have to teach this stuff two nights a week, and yes I am a certified adult education instructor, certified by the Great state of Arkansas. This coming summer I will be getting my Master Electrical license, this test is not easy in the least, 60 questions on electrical code in three hours with up to 20 calculations on service sizes, voltage drop, and many more. If anyone has any other questions on electrical calculations just ask I'll be more then happy to help you. Before anyone says "well you're an electrician that has nothing to do with cars" all electrical calculations are the same no matter what the voltage or if its AC or DC.

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'88 Coupe (extensive mods underway)
https://www.fiero.nl/forum/Forum2/HTML/086359.html

[This message has been edited by HTXtremes (edited 10-06-2007).]

quote Originally posted by HTXtremes: Sorry but (35w +35w +55w +55w = 180w total), to figure your amps using Ohms Law you have (W / V = I or amps) so 180 / 12 = 15 amps. To figure voltage drop you use (2 x K x D x I)/ Circular mils = Voltage drop, (approximate K = 12.9 for copper and 21.2 for aluminum) therefore (2 x 12.9 x 25' x 15) / 6530 Cmils = 1.48 volts lost in a 25 ft run using number 12 wire. For a number 10 wire you would loose .9 volts in 25 ft. Circular mils of wire can be found in any NEC Book (national electrical code) in table 8 in the back of the book. Take it from me on these specs I should know I have to teach this stuff two nights a week, and yes I am a certified adult education instructor, certified by the Great state of Arkansas. This coming summer I will be getting my Master Electrical license, this test is not easy in the least, 60 questions on electrical code in three hours with up to 20 calculations on service sizes, voltage drop, and many more. If anyone has any other questions on electrical calculations just ask I'll be more then happy to help you. Before anyone says "well you're an electrician that has nothing to do with cars" all electrical calculations are the same no matter what the voltage or if its AC or DC.

The stock set up is only low beams (35W + 35W) or just the high beams (55W + 55W) You would need to modify the wiring in order to have the low and high beams on together. Also the low beams are on one wire and the high beams are another wire. Your voltage drop is based on using one wire for both which is not the case.