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Left parking lights/left side marker lights not working
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chuck21401  



Joined: 20 Feb 2005
Posts: 243
Location: Annapolis, MD

PostPosted: Thu Apr 30, 2020 11:24 am    Post subject: Left parking lights/left side marker lights not working Reply with quote

I need some help chasing down a gremlin.

I noticed that the front/rear parking lights as well as the front /rear side marker lights are not working.

The headlights work fine. The turn signals work fine. The hazard lights work.

I have the wiring diagrams from the Haynes manual (and found a scanned version on Pelican Parts). I checked the fuse (14) and it is fine. I replaced the fuse and checked continuity. I'll also cleaned up the contacts but not sure that is the problem.

I've pulled the bulbs and test those in other fixtures, they all work.

I checked the ground at the front of the car near the headlight and in the back near the taillights -both areas are clean and the previous owner had cleaned the contacts and installed a new bolt to ground everything. I believe there is another grounding location behind the fusebox...I need to crawl under the dash to find that one next.

I think the next step would be to check the headlight switch. In looking at the wiring diagram, it looks current flows from the switch to fuse 14 through a grey/black wire. So with the switch on...I should see 12V or so there right? If not, could the switch be bad? It just seems odd that one function of the switch would go bad.





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Last edited by chuck21401 on Thu Apr 30, 2020 11:33 pm; edited 1 time in total
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Paul  



Joined: 02 Nov 2002
Posts: 9435
Location: Southeast Wisconsin

PostPosted: Thu Apr 30, 2020 10:59 pm    Post subject: Reply with quote

With the key out of the ignition and the headlights off, what happens if you activate the turn signals?

This should light the parking lights on the side based on the turn signal lever position.
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
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Porsche: It's not driving, it's therapy.
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chuck21401  



Joined: 20 Feb 2005
Posts: 243
Location: Annapolis, MD

PostPosted: Thu Apr 30, 2020 11:34 pm    Post subject: Reply with quote

Paul wrote:
With the key out of the ignition and the headlights off, what happens if you activate the turn signals?

This should light the parking lights on the side based on the turn signal lever position.


Turn signal right...right side parking lights on.

Turn signal left....nothing.
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Paul  



Joined: 02 Nov 2002
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Location: Southeast Wisconsin

PostPosted: Thu Apr 30, 2020 11:49 pm    Post subject: Reply with quote

If you don't have 12v at fuse 14 with the parking lights on, it is most likely the headlight switch or a bad connection in or on the fuse box.

Check for 12v at fuse box E1 using a test light.
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.
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chuck21401  



Joined: 20 Feb 2005
Posts: 243
Location: Annapolis, MD

PostPosted: Fri May 01, 2020 5:44 am    Post subject: Reply with quote

Paul wrote:
If you don't have 12v at fuse 14 with the parking lights on, it is most likely the headlight switch or a bad connection in or on the fuse box.



I found 12V at fuse 13 with the parking lights on; right side lights working.

I found 0V at fuse 14 with the parking lights on; left side not working.

Quote:
Check for 12v at fuse box E1 using a test light.


Unless I'm confused, I think I'll need to access the back side of the fuse box to do this...I'll need to pull the front seat and hang upside down to do that.

Good timing actually...I'm just about ready to install a new set of freshly covered seats.

So right now the prime suspect seems to be the switch...but there could be a gremlin in the fuse box.
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chuck21401  



Joined: 20 Feb 2005
Posts: 243
Location: Annapolis, MD

PostPosted: Sun May 17, 2020 12:22 pm    Post subject: Reply with quote

I removed the steering wheel and stuck my head under the dash today.

I found the grey/black wire at E1...hmmm looks discolored near the plug!

Before going further I put my voltmeter on the back of the plug at E1...12V with the switch on. Checked for voltage at fuse 14...still nothing.



Finally was able to get it unplugged. Melted plastic...discolored pin.







I tested for continuity at the front of the plug....check...but didn't check for 12V yet.

The previous owner installed fog lights; the fogs are wired into the parking lights. There is no relay. So I'm guessing the circuit was overloaded....and meltdown.

In addition to the melted plug/crispy pin...I'm guessing there is a problem inside the fusebox? Ugh.
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Paul  



Joined: 02 Nov 2002
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Location: Southeast Wisconsin

PostPosted: Mon May 18, 2020 9:35 am    Post subject: Reply with quote

Great job on the pictures.

Do you have continuity from location 1 in the plug to fuse 14?

With the parking lights on confirm you have 12V on E1 in the fuse box. Use a test light not a volt meter.

What size fuse is in 14?

Disconnect the fog lights.
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.
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chuck21401  



Joined: 20 Feb 2005
Posts: 243
Location: Annapolis, MD

PostPosted: Tue May 19, 2020 1:25 pm    Post subject: Reply with quote

Paul wrote:
Great job on the pictures.


I'm 6'4". Almost had my feet sticking out of the sunroof to get under there.

Quote:
Do you have continuity from location 1 in the plug to fuse 14?


Yes. And I was perplexed about that. I was not expecting that.

Quote:
With the parking lights on confirm you have 12V on E1 in the fuse box. Use a test light not a volt meter.


Bought a test light. Yes. Test light lit up at E1 in the fuse box (well, at the plug for EI1 ...but not at fuse 14 when I reconnected the plug.



Quote:
What size fuse is in 14?


White. 8amp. good continuity. Also tried new fuse.

Quote:
Disconnect the fog lights.


Ah ha!

Lights came back on. Test light working at fuse 14.

So what's going on here? Seems obvious that wiring the fog lights into the parking lights caused the issue but I don't understand the findings.

Thanks for your help Paul.



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Paul  



Joined: 02 Nov 2002
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PostPosted: Tue May 19, 2020 11:43 pm    Post subject: Reply with quote

Glad to help. At which point were the fog lights connected? Were they on a switch or always on with the parking lights?
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.
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chuck21401  



Joined: 20 Feb 2005
Posts: 243
Location: Annapolis, MD

PostPosted: Wed May 20, 2020 11:52 am    Post subject: Reply with quote

Paul wrote:
Glad to help. At which point were the fog lights connected? Were they on a switch or always on with the parking lights?


Previous owner added the fog lights when he built the car (81 chassis with 80 transmission/torque tube/engine + wiring harness + green gauges from the 80). The fog lights were from Autozone. I bought a set of Cibie Airport 35s on Ebay from someone in France.

So I believe that they were always on with the parking lights.

At this point I'd like to wire them to a dedicated switch and correct wiring and relay. Ideally would like to use the factory fog light switch which goes under the oil pressure gauge. I've done some digging, the switch is available but finding the correct "pig tail" to go with it might be tough. Euro cars might be different.

Found this pic of the switch elsewhere on this board.

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slowcarfast  



Joined: 03 Jan 2020
Posts: 18
Location: Seattle, WA

PostPosted: Mon May 25, 2020 6:35 am    Post subject: Reply with quote

I think it will be easier to just do your own wiring for the proper fog lights and not worry about the factory harness. Just take switching current for the relay from one of the two low beam feeds, through the fog light switch. Then fog lights can be turned on only with low beams on, and switch off automatically when high beams are on. Power to the relay direct from the battery + post. Run new ground wires from each fog light to the factory grounds at the front of the chassis, left and right. The hardest part is just getting all the bits together. Don't forget cable sheathing!
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slowcarfast  



Joined: 03 Jan 2020
Posts: 18
Location: Seattle, WA

PostPosted: Mon May 25, 2020 6:40 am    Post subject: Reply with quote

Oh, and re the switch, I just put a switch for driving lights in the factory fog light switch position. My new switch is a standard size, but larger than the hole provided. Interestingly, it's the same size as the combo seat belt/brake warning lights hole on the other side of the center console. So I just cut the hole for the switch bigger. Understandable if you don't want to alter the console, tho.
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slowcarfast  



Joined: 03 Jan 2020
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Location: Seattle, WA

PostPosted: Mon May 25, 2020 6:55 am    Post subject: Reply with quote

And I'd also love to know if Paul has a theory on how the added fog lights caused this problem. Maybe it's impossible to say, though, without seeing exactly what the PO did to wire them. The fact that (s)he wired them to the parking lights makes you wonder what other bodges they came up with.
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Paul  



Joined: 02 Nov 2002
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Location: Southeast Wisconsin

PostPosted: Mon May 25, 2020 11:11 pm    Post subject: Reply with quote

Hard to say without knowing how they were connected.

One SWAG is that they were wired between E1 and fuse 14 meaning they were not fused. The overload eventually caused enough corrosion/resistance at the fuse box so that the fog lights soaked up all available current leaving nothing for fuse 14 and the parking lights. This could explain why removing the fog lights from the circuit caused the parking lights to work.
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.
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slowcarfast  



Joined: 03 Jan 2020
Posts: 18
Location: Seattle, WA

PostPosted: Tue May 26, 2020 5:37 am    Post subject: Reply with quote

@Paul : I like it. Sounds reasonable to me.
@chuck21401 : Speaking of fuses, of course you would fuse that new high-current feed to your new fog light relay!
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