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fog lights

Discussion in 'Gen 2 Prius Accessories & Modifications' started by tomdeimos, Jan 14, 2005.

  1. tomdeimos

    tomdeimos New Member

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    Has anyone dealt with the issues of re-wiring the fog lights to work without headlights?

    I gather this may not be legal, but I can tell you for sure it is necessary! My old Mercedes
    could run the fog lights just fine with parking lights on. I didn't have to do it very often
    but when I did it kept me on the road.

    Last night I hit heavy fog and found that the HID lights in fog were worse than most cars
    with high beams on as far as my seeing anything was concerned. I couldn't see 3 feet
    ahead of me. I really missed my switch that let me run the fogs without headlights.

    In fact I don't see the point of the fog lights ever being on with headlights on too! They don't help me see at all that way. The whole benefit of fog lights to me is to get the light coming
    out from the car lower down, so you don't just see a complete wall of white in front of you.
    I could not even see any pavement at all at some points last night and had to just
    assume the road continued straight.
     
  2. IsrAmeriPrius

    IsrAmeriPrius Progressive Member

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    I was taught to use only the low beams of the headlights while driving in the fog and to never use the high beams in those situations.

    By the way, the Prius' fog lights will lit only when the low beams of the headlights are on. They go off the moment you switch to the high beams.
     
  3. popsrcr

    popsrcr New Member

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    >>Has anyone dealt with the issues of re-wiring the fog lights to work without headlights?

    I gather this may not be legal, but I can tell you for sure it is necessary! <<

    Honestly, this has been discussed, but they are driving lights, not real "fog" lights. Fog lights are usually yellow. The color helps cut the fog.
     
  4. tomdeimos

    tomdeimos New Member

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    I would say mine are yellow. But the point is what you call
    them doesn't matter. I could see more with them if I could turn them on
    without headlights, and last night I had to turn off the headlights and drive with nothing
    but the parking lights!

    And till I did that, it wasn't just me being blinded. When I had just my normal low beams on the fog must have made them look like high beams, so for the first time every on coming car flashed at me.

    I never used the so called fog lights at all because they made zero difference in glare
    or visibility. The HID just wiped them out.

    But if they are really not fog lights maybe I just need to add them and take the Prius ones
    out. I see no point to running lights that don't help you see anything better.

    Or maybe they should be wired as DRL's and that would solve my fog light usage problem as well. And if you want them more yellow, I should think bulbs would be
    readily available.
     
  5. tomdeimos

    tomdeimos New Member

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    I think you missed my point. What I said was the HID low beams were worse than
    the high beams on any previous car I have had. Not that I ever put the high beams on
    in the fog. I rarely ever can use high beams at all, due to traffic around here.
     
  6. popsrcr

    popsrcr New Member

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    Hum. They do call them foglights. I just think the yellow would help more.
    I did drive in some fog here with the HIDs. Probably not as bad as what you experienced. Didn't suck much more than normal.
     
  7. IsrAmeriPrius

    IsrAmeriPrius Progressive Member

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    You may have meant it; however, you did not write it quite that way.

    This is what you wrote:

    The words "Low beams" did not appear anywhere in that post.
     
  8. tomdeimos

    tomdeimos New Member

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    You're right I guess I didn't mention low beams, I just assumed everyone would know I wouldn't try to use high beams.

    So now I am wondering did all cars make their fog lights
    pretty much useless during the last 15 years or so, or is it
    mostly Japanese cars that make them turn off without the
    headlights on.

    My old Mercedes I was driving was a 1987 and I have used it
    in regular fog with both sets of lights on, and with just fog
    when visibility got down into the 5-15 ft range.

    The Prius ones I will have to re-wire before I can even tell
    if they would work as well, since they are washed out by the
    HID.

    I think much of the problem is the HID are at high beam
    intensity full time. Only the aim changes for low beam, but
    the fog spreads out all the light anyways.

    Note I'm only talking about unusually bad fog, but some blizzard snow conditions could be like this too around here
    and be more likely.
     
  9. Frank Hudon

    Frank Hudon Senior Member

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    wow someone else who found the fog lights one notch better than p**s useless. This subject was beaten to death last winter and spring on PC, do a search on them and read up. Yup fancy junk! useless in real fog.
     
  10. DanMan32

    DanMan32 Senior Member

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    I understood him fine.

    The HIDs light up the same intensity, 'low beam' or 'high'. A shutter masks the top rays in low beam mode, and move out of the way in high beam, thus throwing out light upward as well.

    So with that much light, fog can definitely reflect it back in all directions.

    I agree, the fog lights are useless. They are drowned out with the HID lights. They'd be more useful if they could be turned on without headlights.
    And they will seem yellow compared to the more white HIDs.
     
  11. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    I think it's interesting that after all those posts, not a single person seems to have addressed rewiring the lights. :)
     
  12. IsrAmeriPrius

    IsrAmeriPrius Progressive Member

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    <div class='quotetop'>QUOTE(tomdeimos\";p=\"63550)</div>
    The Prius replaced my 1987 MBZ 300E which I drove for 17 years and four months for a total of almost 217,000 miles.

    <div class='quotetop'>QUOTE(DanMan32\";p=\"63553)</div>
    So, DanMan, you are the expert in these matters, is it doable?
     
  13. DanMan32

    DanMan32 Senior Member

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    Hmm, a challenge. I love it!

    It looks like one end of the fog switch on the combo switch connects to the body ECU, which in turn engages the fog relay to turn the lights on.

    Now the other side of the fog switch connects to an orange wire, which connects to a blue wire through a terminal block, and goes to the low beam side of the headlight dimmer, which isn't used for anything else. It seems if you feed ground to the orange wire after disconnecting it from the junction block, the fog light could come on any time. At first I thoght that might defeat the auto off, but I think the body ECU will turn it off automatically no matter what you feed to to the fog terminal.

    Will have to do some trial runs.
     
  14. DanMan32

    DanMan32 Senior Member

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    Someday I'll tackle full-Auto DRL, but I suspect I'll have to get the DRL ECU and sensor. I am suspecting that may not be cheap, and I'll have to get that from Canada.
     
  15. tomdeimos

    tomdeimos New Member

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    I just took a look too at the wiring and that junction block stuff looks like
    Toyota actually intended to disable these things for the US but just jumper
    differently and they'd work for other places!

    I'll definitely be rewiring mine before I drive in fog like that again I hope! Looks like I just need to jumper pin 14 to 15 on that jumper block. Just
    let me know where it is, if you find it first Dan! And I hope you are right
    that the ECU will kill it, but if not and I forget the switch, I'll get to use my
    Coleman backup battery!

    And thanks everyone regarding the archive info, I'll start reading the stuff
    I missed. I think I vaguely remember some fog light discussions, but it
    seemed so much less important while I was just waiting for a car!
     
  16. DanMan32

    DanMan32 Senior Member

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    Well, I tried to ground the sky blue wire, pin 4 on the combination switch, which goes to the body ECU for the fog light. Unfortunately, the body ECU is too smart, and won't turn on the fogs unless the headlights are on low. They won't come on with highbeams even if I ground the SB wire going to the ECU, bypassing the dimmer switch, so I don't know why they make use of the low beam switch for the fog.

    So Tom, jumpering pins 14 and 15 won't do it.

    We could bypass the body ECU and turn on the fog relay ourselves. If we don't mind turning on the fogs only when the tail light is on, then we can jumper the SB wire on pin 13 at the ECU to the yellow wire at pin 17 on the ECU. The tail lights go off automatically, and the fog relay gets its power from the tail lights, so it will cut out automatically, and turn off the fogs.
     
  17. jayman

    jayman Senior Member

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    <div class='quotetop'>QUOTE(Frank Hudon\";p=\"63552)</div>
    Are they ever. Purely cosmetic and better left off. A "real" foglight, like a Hella with a yellow lens, would work wonders.

    You could wire the real foglights on a separate circuit, and put the headlight switch to Park. I'm not sure if that would be legal in the U.S. or Canada though.

    Headlight aim is very important for driving in snow, rain, and fog. After I had my headlights properly aimed at an Autopac-certified bodyshop using a digital reference aiming machine, nighttime performance in poor conditions was much improved.

    If the headlights are dirty with slush/salt or road grime, the light can be diffused or diffracted. I've noticed this driving on slushy roads in Winnipeg. I frequently have to stop at a gas station to squeegee the headlights. Here is wishing for headlight washers/wipers.
     
  18. tomdeimos

    tomdeimos New Member

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    Thanks for the bad news Dan.

    Guess the ECU bypass is the way to go then. I'll start looking for a switch
    to fit the little slots next to the smart entry disable button.
     
  19. Tideland Prius

    Tideland Prius Moderator of the North
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    Can you change the bulbs to better ones? would that work?
     
  20. ammiels

    ammiels New Member

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    DanMan, Please let us know when you succeed. I asked Wonderful Wayne to look into this a year ago and he said he would. But he has dissappeared. You really want only the fog on when you need near illumination. When really needed it does not light the road very far, but enough so you can stay on the road while you slow down.
    I know I can get an ign switched hot to switch an add-on relay and bypass the OEM, but there oughtabe a better way.