dim tail lights

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Mar 22, 2016 | 03:40 PM

hdrider1957

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Cruising

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From: Peoria illinois

dim tail lights

i have a 1988 c4 corvette project car I have it running great but the problem i have is the headlights are nice and bright but the tail lights and fog lights are very dim. Could i please get some ideas where to start
Relays, grounds etc

Mar 22, 2016 | 06:52 PM

WVZR-1

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Quote:

Originally Posted by hdrider1957

Generally speaking you can't have it the way you describe. If ALL ARE DIM that would seem to be a voltage problem at the lamp socket BUT if it were low at those then the HEADLAMPS would also be dim.

You need to start with maybe a quality check of the battery/charging system. Do the lamps brighten when the RPMs of the engine are increased? When you say dim- are they all dim? You say yes but don't explain very well. Check voltage at multiple sockets for confirmation.

Incorrect bulbs might contribute but you mention ALL so that seems very unlikely.

Mar 23, 2016 | 12:43 AM

Cliff Harris

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From: Anaheim CA

The fog light wiring is protected by the TAIL fuse, which is also where the power comes from for the tail lights. I suspect a problem in the fuse or fuse block.

Mar 23, 2016 | 08:47 AM

WVZR-1

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Quote:

Originally Posted by Cliff Harris

The fog light wiring is protected by the TAIL fuse, which is also where the power comes from for the tail lights. I suspect a problem in the fuse or fuse block.

TAIL fuse is the starting point for sure - all exterior lamps should be dim. If you've 12V at the TAIL fuse then the issue would be between the fuse and the light switch, if you've 12V to terminal F on the light switch then well ........

Checking at the light switch is NOT easy.

I'd think you maybe need to check the entire fuse block for correct voltage paying particular attention to the CTSY/CLK also as I believe in the earlier C4 the same fusible link supplies TAIL and CTSY. If less than 12V to either maybe the fusible links behind the battery at the jump block would be the next to look at.

Last edited by WVZR-1; Mar 23, 2016 at 08:49 AM.

Mar 23, 2016 | 01:52 PM

Churchkey

Melting Slicks

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From: Cherokee National Forest TN

Rear turn/stop lights bright? If so the grounds are good. If not bright you have a poor ground connection. Frame rail corrosion @ the ground connections under the battery box is common. IIRC the tail light ground is somewhere else my 8A electrical manual is currently unavailable = no help as to where it might be. Probe a black tail light wire & connect a jumper wire to a good ground to test. Also probe a brown tail light wire & check volts, should be within a few tenths of battery voltage. If not the above info will help get things sorted.

Good luck

Mar 23, 2016 | 06:46 PM

WVZR-1

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Quote:

Originally Posted by Churchkey

Name: G401 Coupe early.png
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Name: G401 'vert early.png
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FOGS are grounded through G115 & G116 top of frame rail behind park light (near horn) on each side. Is it possible to have all grounds faulty? Yes. So like Cliff mentioned check fuse block for 12V (or close), then create your own grounds with a jumper and check as "Churchkey" mentioned.

Don't forget to "POST BACK"!!

Mar 24, 2016 | 10:52 AM

hdrider1957

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Cruising

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From: Peoria illinois

fog lamps

OK i took the fog lamps out of the cars regular wiring system and simply made my own wiring harness for the fog lights with switch, relay and in line fuse. This took care of the problem, Thanks for the help \\

Quote:

Originally Posted by WVZR-1

Create your own grounds as suggested or the TAILS are all grounded through G401 I believe and here's a couple images from an early FSM, coupe (near center of lock pillar), 'vert (behind passenger seat).

Attachment 47966062

Attachment 47966063

FOGS are grounded through G115 & G116 top of frame rail behind park light (near horn) on each side. Is it possible to have all grounds faulty? Yes. So like Cliff mentioned check fuse block for 12V (or close), then create your own grounds with a jumper and check as "Churchkey" mentioned.

Don't forget to "POST BACK"!!

Mar 24, 2016 | 11:20 AM

WVZR-1

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Quote:

Originally Posted by hdrider1957

Tails are fine now? Had you modified the fogs/increased wattage prior to the tail "dimming" you had mentioned and that created the issue?

I believe I'm understanding what maybe created your issues.