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Old 04-20-2004, 09:07 PM   #1
TheCorvetteKid
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Default Just finished the 880 -> 885 fog light upgrade, and...

...while the upgrade went fairly easily, I noticed something odd happened when I turned on the fog lights - my headlights glowed (dimly)! Is this normal?

Just to retrace my steps for a second, I replaced both of my stock 880 fog light bulbs with new GE 885 bulbs. I pulled the 10A brake lamp fuse and replaced it with a 15A one, just as the posted tech article specifies. I then pulled the light switch to the first detent. The parking lights came on, and the headlights remained off and in the 'closed' position. When I turned the fog lights on, the head lights glowed dimly, and still in the closed position. I pulled the switch to the second detend and the headlights came on and the light assemblies rotated to the 'open' position, as normal. With the lights in the 'open' position, I pushed the headlight switch back to the first detent, and again the headlights glowed dimly.

Is this normal? I'll be honest, I never noticed if my car did this with the original 880 bulbs. If anybody here wouldn't mind just running out to their garage and turning on their headlights and fog lights (pull the switch to the second detend), then turn just the head lights off (push the switch back to the first detend) and see if their headlights also glow, I'd really appreciate it. Especially those forum members that have done this 880 -> 885 conversion. I want to find out if my wiring is all screwed up.

Thanks in advance.

P.S. Other than this problem, I would whole heartedly recommend this upgrade. While I can't conclusively say that the new lights are THAT much brighter than stock (the car is in a fully lit garage, so I won't be able to comment until the car hits the road) for the cost, it's certainly worthwhile.
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Old 04-21-2004, 12:40 AM   #2
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Default Re: Just finished the 880 -> 885 fog light upgrade, and... (TheCorvetteKid)

Stock setup for now except I have already replaced the 10 amp fuse with a 15 amp. I only get light from the headlights when I fully pull out the ****. The rest of the settings do not result in any glow in the headlamps on my 87. Now, how do you get access to the fog light bulbs to remove them? I can see how to get the running light/turn signal bulb out but it looks impossible to pull the fog light sockets as the hood hinges are in the way. Anyone :confused:
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Old 04-21-2004, 02:50 AM   #3
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Default Re: Just finished the 880 -> 885 fog light upgrade, and... (TheCorvetteKid)

Your not getting the full effect of the new bulbs. In some of the later c4's they grounded the fog lights through the highbeam filament of the headlight. you need to find the ground for the headlights, cut the wire, and ground the headlight and foglight seperately. I had to do the same thing on my '88. there are some tips on here about it if you can find them.
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Old 04-21-2004, 09:42 AM   #4
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Default Re: Just finished the 880 -> 885 fog light upgrade, and... (TheCorvetteKid)

I agree. I think you have a grounding issue.

Art
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Old 04-21-2004, 01:15 PM   #5
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Default Re: Just finished the 880 -> 885 fog light upgrade, and... (TheCorvetteKid)

The 89-back, use a ground thru the headlamp. When the headlamp go to high beam, this effectively cancels the ground, 2 positives on the road lights causes them to go out. The 880 bulbs don't draw as much current as the 885s. The current draw is actually causing the high beam filament to glow on the stock lamps due to resistance of the lamps.

On the air inlet to the radiator is a wire bundle that has the foglights power and ground, don't remember the colors, I THINK Hot ones are blue and other blue w/white stripe, DON'T QUOTE ME.

Anyway, cut the grounds loose, you can trace back to the lights and I think they're black, vtvm them out, take the grounds, tie them together, buttsplice another piec of wire and heatshrink the connection and ground them to the chassis. Problem will be solved.

These lights used the headlamp filament as a path to ground, it does not affect the headlights, except to keep them from glowing.

The 90s up do not have this problem, the road lamps are separately grounded and are powered by the low beam circuit, which of course turns off on high beam. To keep the road lamps on on high beams requires a different high beam circuit or a switched relay to keep them on.

One last thing you can do to is put a diode on the circuit to block the path back to the low beam circuit when on high, keeps highs and lows from being on at the same time, best to do it behind the dash, but you can do it at the headlights too.


[Modified by johnnyevans, 1:20 PM 4/21/2004]


[Modified by johnnyevans, 1:41 PM 4/21/2004]
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Old 04-21-2004, 02:32 PM   #6
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Default Re: Just finished the 880 -> 885 fog light upgrade, and... (johnnyevans)

This sounds like something I may want to do to my '91. If I understand correctly, the power would come from the low beam circuit. If I increase the wattage of the Driving Lights (Fog Lights?), would the low beams then be dimmed to a glow as was described for the high beams?
TIA
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Old 04-21-2004, 04:11 PM   #7
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Default Re: Just finished the 880 -> 885 fog light upgrade, and... (olefam)

Its a grounding problem...I don't have it on my "94"...and I did the mod a few years back :cheers:
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Old 04-21-2004, 05:59 PM   #8
TheCorvetteKid
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Default Re: Just finished the 880 -> 885 fog light upgrade, and... (69mako)

I had a feeling it was a grounding issue. In fact, it's kind of a relief - I was worried it was a problem caused by a previous owner or some bone-head mechanic messing around with the wiring and getting things crossed.

It figures that the problem wouldn't exist after the '89s! It's always the case.

But thanks for all the help. I really do appreciate it. I will take a look at fixing the issue this weekend since the car is still up in the air undergoing spring-time preparations.

Although I do have the service manual and johnnyevans' directions are great (thanks Johnny!), if anyone has any pictures or 'simplifed' wire diagrams, please feel free to post them. Anything to make the job easier...

Thanks again guys! I'll make sure to post the results once I've got the problem all taken care of.

:cheers:
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Old 04-21-2004, 09:21 PM   #9
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Default Re: Just finished the 880 -> 885 fog light upgrade, and... (olefam)

Glenn
No, it won't affect the low beams at all. There is a fuse in the circuit, don't remember which one, go to 15 amps, it won't hurt a thing.

They also have a high output turn/marker lamp that is clear, I think its 28-30 marker and 45-50 turn, watts. I don't think that I would use them without a relay circuit set up, it probably would be all right, but you're adding about 30% more load on the turn signal switch and I don't know how well it would hold up. It would probably hold up, but the vettes system wasn't designed for towing, so I don't know how heavy duty it is.

I may have been a little misleading on the low beams providing power to the road lamps, the switch is actually controlling the circuit for the road lamps, but if you wire the lamps to stay on while on high beams, it will back feed through the switch circuit circuit and keep the low beams on with the highs. That's the reason for the XXXX XXXXX. darn it, went to modify and forgot! Try this:
That's the reason for the blocking diode.
On the 90s up you can cut the wire and have the road lights switch hot at all times, or go the blocking diode method.

If you need it, I'll lay a circuit out for you with a few how tos. I'll get it scanned and send you a copy if you want it, unless you have AutoCad or WP 10-11, they can read a dxf file. I can lay you a diagram for the 89 and 90, they should be the same down and up, just maybe wiring colors.




[Modified by johnnyevans, 9:30 PM 4/21/2004]
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Old 04-24-2004, 10:06 AM   #10
TheCorvetteKid
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Default Re: Just finished the 880 -> 885 fog light upgrade, and... (johnnyevans)

Hi Johnny,

Thanks for all the help. Still haven't gotten under the hood to fix the problem, but a circuit diagram drawn on AutoCAD would be a big help. If you have one, or can whip one up quickly, please email it to me.

Thanks again for the help.

:cheers:
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Old 04-24-2004, 10:06 AM
 
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