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Fog lights

Paul G

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Joined
Aug 27, 2001
Messages
200
Location
Griffith, IN, USA
Corvette
96 CE LT4 Convertible
Both of my fog lights went out at the same time. I thought for sure it was a fuse, or switch or something. But, both bulbs were burnt out at the same time. I replaced the original 34 watt bulbs with the 50 watt bulbs. I noticed that when I have the driving lights on (pull the headlight switch out to the first click, headlights not on yet) and turn on the fog lights, the headlights were glowing dim, and the fog lights were no brighter than before. I pulled out the Helms manual, the schematic shows that the later 88 which I must have, run the fog light current path to ground through the high beam filiment of the headlights. That is why the headlights are glowing dim with the just the fog lights on. The manual shows the early 88 the fog lights go directly to ground. I grounded the lt green wire from the fog lights and they glowed at full brightness.

Anyone know why GM changed this? Can they be switched over to the early 88 configuration?
 

Paul G

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Joined
Aug 27, 2001
Messages
200
Location
Griffith, IN, USA
Corvette
96 CE LT4 Convertible
After thinking about this a little it seems GM's intent might be to have the fog lights turn off when the high beams are switched on. That is the only reason I can come up with. (Maybe I answered my own question).

Any other thoughts???
 

69MyWay

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Jul 3, 2001
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4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
Paul, I have not reviewed the wire schmatic, but I would imagine that the fog lights share the same ground as the high beams/head lights. I would think that you are back feeding somewhere due to a poor ground.

I would clean all front body ground contacts and see what happens. Otherwise, I can't make any sense out of what you are discovering there. I don't know why they would do it that way.
 

Paul G

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Joined
Aug 27, 2001
Messages
200
Location
Griffith, IN, USA
Corvette
96 CE LT4 Convertible
69MyWay said:
I would think that you are back feeding somewhere due to a poor ground.

I would clean all front body ground contacts and see what happens.
That was my first plan of attack. With no success. After looking in the manual (the electrical supplement manual shows the change took place late in the model year) it is clear that the fog lights current path to ground is through the high beam filament. With the fog lights bypassing the high beam they are as bright if not brighter than the headlights. That is what I wanted.
 
T

Tonylong

Guest
Paul. I've been following this topic because I also wanted to "righten" my fogs.
I have an '89. I just went to the vette and tried the various positions:
parks on - allows the fogs on
Low beam on - allows the fogs on
High beam on - Turns OFF the fogs !!

It looks like your theory was correct.
I know my wiring is unmodified.
The General doesn't want the High beams and fogs on together - actually it makes sense.
I alsol have a '95 Jeep Wrangler and it works the same way (high beam on = fog off).
If you use the fogs in fog - then you don't want any excess light as it will cause glare back.

BTW did you use clear or amber lights.
I want use brighter AMBER lights in their place.
HTH
 
T

Tonylong

Guest
Follow up post
I repeated your first test:
Pull switch to first detent (park only)
and turned on fogs.
Fogs lit OK as expected.
NO headlamp on even dim.
I used voltmeter - no volts on either Hi or Lo
filament.
You may still have a wiring problem, or bad ground.

LOL
 

Paul G

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Joined
Aug 27, 2001
Messages
200
Location
Griffith, IN, USA
Corvette
96 CE LT4 Convertible
Tony, Do you still have the original 34 watt lamps in your fog lights? Simple Ohms law states that the highest voltage drop will occurr across the path of highest resistance. Since I switched from 34 watt to 50 watt fog lamps the resistance went down. They are getting less voltage now. Which means the headlamps are seeing more voltage and they now glow where they didnt before. Thats why the fogs are no brighter with the 50 watt lamps. My high beams did not glow until I switched to the 50 watt lamps in the fogs. I am going to open the wire harness and look for the conection point where the lt green fog light wire ties in to the lt green high beam wire. Early 88 has a purple wire feeding power to the fog lamps and a black wire to ground from the fog lamps. My late 88 has the purple wire feeding power to the fog lamps with a lt green wire on the return side of the fog lamps. lt green is the same color wire the high beams use.

Does this make sense? Or am I screwed up?
 

Paul G

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Joined
Aug 27, 2001
Messages
200
Location
Griffith, IN, USA
Corvette
96 CE LT4 Convertible
Tonylong said:

BTW did you use clear or amber lights.
I want use brighter AMBER lights in their place.
HTH

I dont know why they call them fog lights when thay are clear? I used clear again. It doesnt go out in bad weather. I like to put on the fog lights without headlights around dusk. I think it looks cool. I just wanted them bright enough to actually see something.
 
T

Tonylong

Guest
yeah I still have tho original lights in.
I haven't yet located amber's @ 50 watts.
I won't put amber 34's in they won't be bright enough.
 
E

Eagle85C4

Guest
I put 50's in mine and the headlights work as normal, with just the fogs on there is no indication or voltage from the head lamps....
 
Joined
Oct 30, 2001
Messages
2,273
Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
Not sure which bulb the Vette uses for its fogs. I'm used to 50w fogs normally in my Subarus - I upgraded to 80w all-weather dichroics in my Outback. Made a *huge* difference. But if you're looking for oddball colors/wattages try http://www.hioutputbulbs.com/ . Gene has been serving rallyers for years and has a ton of stuff.
 

Paul G

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Joined
Aug 27, 2001
Messages
200
Location
Griffith, IN, USA
Corvette
96 CE LT4 Convertible
Found the answer to my problem

I am attaching a link to another thread that explains why my high beams are glowing. I am going to need to cut the lt green wire loose and attach it directly to frame ground as I suspected. Anyone who wants to do this upgrade may have to do this also if your fog lights use a purple and lt green wire. If yours have a purple and black wire, the black wire is already conected to frame ground. All you need to do is upgrade to an 885 lamp.

Paul G.

http://www.corvetteforum.com/techtips/viewsubtopic.php?SubTopicID=52&TopicID=2
 

BigRed

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Joined
May 23, 2001
Messages
948
Location
Edmonton
Corvette
1985 Bright Red Rocket
Thats sounds like something Im going to do as well. I have a couple PIAA fog lights (Egg's) and I was going to encorporate them in to stock housing through the stock lens which will give me Serious light as well as really good looks. What do you guys think? (I believe they are 50 -65 watts)
 
T

Tonylong

Guest
Paul - re your first two posts -
I checked my Vette shop manual.

Wiring the fog lites to the hot side of the high beams is the General's cheap a$$ way of turning the fogs off when the hb's are on.

That puts the same voltage onh both sides of the fogs - resulting in no flow across the fogs !
The fix is as you described - wire the lt grn directly to a ground. The fogs are still linked to the main light switch, and will turn off with main lights, but will stay on with hoigh beams on.

Sheeesh - even my el cheapo Jeep used a separate relay fot the fogs, tripped by the HB's.

LOL
 

Paul G

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Joined
Aug 27, 2001
Messages
200
Location
Griffith, IN, USA
Corvette
96 CE LT4 Convertible
You got it exactly Tony.
Last night I opened the lt green wire at each of the fogs, conected a black wire to it and tied it directly to ground under the horns. Now my fogs light up at the full 50 watts. What a difference!!! Only thing is they stay on with the high beams on. I dont see anything wrong with that.

What had me going was the wiring scheme for the late 88 model's is only shown in the electrical supplement manual. If you dont look there first you would the swear the problem is a bad ground. (the general got me)

A relay to open the fog light circuit when the high beams come on would be the correct way to accomplish the task. The general took the cheap route.

Paul G
 
8

86targa

Guest
fog lites can be either amber or clear. The way they work is they are mounted low so there is not as much glareback in the drivers eyes, even better than low beam. also being that low also puts them usually in an area just above the ground where its usually clear in fog. Usually fog is above 12 to 18 inches above the ground and up.
 

Corvette-Pilot

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Joined
Sep 25, 2002
Messages
484
Location
Dracut MA
Corvette
1994 Black Rose Coupe
Paul G said:
I dont know why they call them fog lights when thay are clear? I used clear again. It doesnt go out in bad weather. I like to put on the fog lights without headlights around dusk. I think it looks cool. I just wanted them bright enough to actually see something.


Fog lamps have a short range and wide area.
Driving lamps are long range and very narrow.

It makes no difference what color they are, it refers to the beam pattern.
 

Corvette-Pilot

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Joined
Sep 25, 2002
Messages
484
Location
Dracut MA
Corvette
1994 Black Rose Coupe
rrubel said:
Not sure which bulb the Vette uses for its fogs. I'm used to 50w fogs normally in my Subarus - I upgraded to 80w all-weather dichroics in my Outback. Made a *huge* difference. But if you're looking for oddball colors/wattages try http://www.hioutputbulbs.com/ . Gene has been serving rallyers for years and has a ton of stuff.

This is part of the reason the fogs/driving lights go out with high beams. My neighbor was pulled over because the cop thought he had his high beams on and they were too bright. Turns out he had the low beams and a set of factory driving light on his Jeep. The cop told him to switch to high beam because he wanted to see if the lamps went off as they should. Luckly me neighbor was able to flip the manual switch at the same time as he hit the high beams and he was let go.

The cop told him that since all these high power lights started hitting the streets it has become a big problem for others to see when approched by these lights. I know some of these lights warn they are for off road use only but ofcourse this doesn't stop anyone !

At least that was the scoop I got for the MA area.
 

Redbob

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Joined
Dec 5, 2001
Messages
239
Location
Cross Roads, Texas, U.S.
Corvette
'89 dk red coupe
Paul G said:
I grounded the lt green wire from the fog lights and they glowed at full brightness.

Thanks for that tip; I just did the same thing to my ('89) car, also noticed the main beams glowing, just haven't worried much about it. But like you said, the fog lights weren't any brighter with the 50W bulbs.
In fact, I've been thinking of converting the foglamp housings to cold air intakes. Has anyone else done this?
Thanks,
R
 
L

LOUVETTE

Guest
reply

my fog lamps are turned on by pushing the switch on the right side with the little dot......is something backward .... should they be turned on by pushing the left side with the little half circle and black center with rays comming off it or is this the right way to turn them on......
 

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