Rear fog light on 73 tii

[02Les]

that looks my Baroness but the wheels is on the wrong side

No Rob, it's on the right side. Right = another word for correct. he he.

[Clint]

Greetings Armond -

Thanks for your reply with the info and photo. The Fog Light you have on your car is exactly what I am looking for...do you have a Hella part number for the light shown in the photo? Would you have a source for this Hella light?

Thanks,

Clint

[jdt10768]

I am planning to install one of these things sometime soon.

Interested in using it as 3rd brake light, and also having it turn ON when I turn the headlights on --> and to increase intensity to ludicrously bright when brakes are applied.

 

Can anyone shed light (ha ha) upon the wiring procedure to achieve this result?

Thanks!

 

 

[adawil2002]

16 minutes ago, jdt10768 said:

I am planning to install one of these things sometime soon.

Interested in using it as 3rd brake light, and also having it turn ON when I turn the headlights on --> and to increase intensity to ludicrously bright when brakes are applied.

 

Can anyone shed light (ha ha) upon the wiring procedure to achieve this result?

Thanks!

 

 

 

I'm no electrical expert. It sounds like you'll need a dual filament bulb in the light. Then run a wire to the headlight switch and tap into the switch on power side and ground. Then another set of wires to the brake light terminals. Be sure to put inline fuses in the circuits. Advise buying the red Haynes manual or the Prospero's Garage wiring diagram. Running the circuit to the headlight switch will be the tough part.

Edited March 13, 2017 by adawil2002

[MoBrighta]

54 minutes ago, jdt10768 said:

I am planning to install one of these things sometime soon.

Interested in using it as 3rd brake light, and also having it turn ON when I turn the headlights on --> and to increase intensity to ludicrously bright when brakes are applied.

 

Can anyone shed light (ha ha) upon the wiring procedure to achieve this result?

Thanks!

Be glad to help- After half a million miles on my 1972 2002, I had the wiring memorized!

 

I have been doing a rear fog light conversion to tail + brake light for decades.  Also have done conversions with working rear fog lights to provide tail and brake AND rear fog, all in the same light.

 

There are ways to tap into the wiring in the trunk going to the stock lights, and no need to run a relay unless you want to - I think it's a good idea, and did it in mine, so I would recommend it.

 

I would be happy to build you a harness that plugs in, just like the original wiring, and avoid alligator clips and cutting / damaging the original wires.  Get in touch via email, we can work out the details and cost. I also want to know more about the rear fog light - specifically wiring details, and what the lamp socket looks like. 

 

Maybe you'll want high output lamps?  Not high wattage, to avoid issues with fuses, wiring, or lenses melting of course.

 

Andy

[jdt10768]

2 hours ago, MoBrighta said:

Be glad to help- After half a million miles on my 1972 2002, I had the wiring memorized!

 

I have been doing a rear fog light conversion to tail + brake light for decades.  Also have done conversions with working rear fog lights to provide tail and brake AND rear fog, all in the same light.

 

There are ways to tap into the wiring in the trunk going to the stock lights, and no need to run a relay unless you want to - I think it's a good idea, and did it in mine, so I would recommend it.

 

I would be happy to build you a harness that plugs in, just like the original wiring, and avoid alligator clips and cutting / damaging the original wires.  Get in touch via email, we can work out the details and cost. I also want to know more about the rear fog light - specifically wiring details, and what the lamp socket looks like. 

 

Maybe you'll want high output lamps?  Not high wattage, to avoid issues with fuses, wiring, or lenses melting of course.

 

Andy

Thanks Andy, will give you a shout soon!  John

[Simeon]

7 hours ago, jdt10768 said:

I am planning to install one of these things sometime soon.

Interested in using it as 3rd brake light, and also having it turn ON when I turn the headlights on --> and to increase intensity to ludicrously bright when brakes are applied.

 

Can anyone shed light (ha ha) upon the wiring procedure to achieve this result?

Thanks!

 

 

 

That will need some trick bulbs. The normal brake light bulb is 21W and the normal fog lamp bulb is 21W so what you need is a dual filament bulb of 21W and ... ? plus the wiring to run it. 

 

Maybe do do it with a front fog lamp running H4 bulb and coloured red?

[xferboy]

If you were to wire the marker lights to the rear fog light with a resistor inline (7 ish ohm should be 1/2 voltage, probably less than 1/2 intensity), and a second run with out  a resistor from the brake lights, you should be able to achieve what you're looking for.  You'll need a couple of diodes (2 amp) to prevent back feeding the other circuits.

 

If you think that might be what you're interested in, I could draw up a circuit (to make it clearer) and calculate values for you.

 

Alternately, an arduino, some FET's, could provide endless options (Pulse width dimming, Flashing brake light, SOS, etc)

 

[jdt10768]

14 hours ago, xferboy said:

If you were to wire the marker lights to the rear fog light with a resistor inline (7 ish ohm should be 1/2 voltage, probably less than 1/2 intensity), and a second run with out  a resistor from the brake lights, you should be able to achieve what you're looking for.  You'll need a couple of diodes (2 amp) to prevent back feeding the other circuits.

 

If you think that might be what you're interested in, I could draw up a circuit (to make it clearer) and calculate values for you.

 

Alternately, an arduino, some FET's, could provide endless options (Pulse width dimming, Flashing brake light, SOS, etc)

 

sure, any help appreciated xfer, and I'm sure others would appreciate the documentation as well

Thanks!

[xferboy]

Give this a whirl:

 

I am assuming we're going to use a 21 watt bulb, and the bulb wattage is calculated at 12v

 

First, let's find resistance of the bulb  (I'll go measure later)

 

21w=(v^2)/r

144/21 = r = ~6.85 ohm

 

For simplicity of picking components lets use a 10 ohm resistor for the 'dim' side of the circuit.  Other values (for 5% resistors) are 6.8, 7.5, 8.2 and 9.1)  You'll have to re-calculate for values other than 10.
 

We'll need some diodes.  We only need to worry about current capability of the diode (we're no where near reverse voltage in this circuit) 

For sizing I'll use 14.4v.  When ever is subtract .7 that is the voltage drop across a diode.

 

for the Brake light diode, you'll need at least a 2 amp diode

(14.4v-.7)/6.85r=2 amp on the nose.  I'd go bigger.  2.5, 3, 5 amp.

You could get a single big diode, or put 3 1amp diodes in parallel.  (1N4001, very common, $1.50 for 10 online hobby pricing )

 

The marker light side won't be passing as much current

(14.4-.7)/(10+6.85) = .8 amp.

One 1 amp should be good

 

Now to size the resistor  (I^2)*R

(.8^2)*10 = 6.4Watt - probably 10watt 10ohm for ease of sourcing

By the way, the bulb output will be:

(.8^2)*6.85 = ~4.4 (just lower than the marker lights)

 

So, you'll need a 10 watt 10 ohm resistor (about the size of a small bic lighter) and either a 3 to 5amp diode and a 1 amp diode.  Alternately, you could use multiple (3) diodes in parallel for the brake light and one for the marker side. 

 

If you use a smaller ohm value resistor for more intensity, 10 watt should be fine for all sizes listed above. If you use a 6.8, you'll need diode that can handle more than one amp (or 1 one amp in parallel)

 

I think that should be all.

 

Diodes can be soldered, just be some what quick so you don't cook them.

 

Hope that helps.

 

Allan

Edited March 15, 2017 by xferboy
Fixed equasion

[ray_]

Pretty neat, Allan.

 

If it were me, I'd seek some way to use a bright LED or array of them... not that that would look very period.

 

 

Cheers,

[xferboy]

Could be fun setup as an extra marker/3rd brake, and fog using LED's.

 

3 levels of brightness.

 

Since the price of period correct rear fogs has been creeping up, has anyone found a modern one (Gates, Bosch, Hella, etc) that has the right look but isn't crazy expensive?  I've always thought that the slim chrome round lights look right on a round tail.

[pklym]

From the FAQ, I believe Mike Pugh. I had edited a copy to try to make the rear light also turn on with the hazards, but upon looking at it again now, I don't think it was right.

[jdt10768]

8 hours ago, xferboy said:

Could be fun setup as an extra marker/3rd brake, and fog using LED's.

 

3 levels of brightness.

 

Since the price of period correct rear fogs has been creeping up, has anyone found a modern one (Gates, Bosch, Hella, etc) that has the right look but isn't crazy expensive?  I've always thought that the slim chrome round lights look right on a round tail.

 

I bought this one to use http://www.ebay.com/itm/232199955309?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT  but didn't pay full asking price/make an offer

free shipping from Germany, not bad

Thanks for the diagram xfer, I am an electrical illiterate but have friends who know what's going on

I will post final result!

[xferboy]

7 hours ago, pklym said:

 

I see what this one is doing.  Kind of a sneaky/different (good) way of using a relay.

 

When the relay is in its normal state (not energized), the Normally Closed (NC) 87a connector will allow current to pass from the brake lights (when on) and light up the rear fog.

 

When the rear fog light switch is closed, current will flow to energize the relay, allowing current to also flow through terminal 87 and to the light.