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No Left High Beam Headlight

 
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slowcarfast  



Joined: 03 Jan 2020
Posts: 17
Location: Seattle, WA

PostPosted: Sun Apr 26, 2020 6:21 am    Post subject: No Left High Beam Headlight Reply with quote

Hey all. New-to-forum user here, and this is my first 924. The car is in good shape: it runs, it drives, and, after a braking system overhaul by a professional garage, it stops as it should. I've been enjoying driving it while taking care of relatively minor stuff myself. Currently I'm trying to get the left high beam working. Here's what I know:

It's not the bulb in the headlight (new H4 unit, tested); it's not the fuse (new fuse, tested). With the high beams ON: Right high beam is on; I have current on both sides of the left high beam fuse; I do NOT have current at the 3-wire connector that feeds the headlight pigtail; I do NOT have current on the downstream (wire) side of the "A" plug on the main electrical panel. If I unplug the "A" plug (battery disconnected!), I DO have continuity between the socket (A18) and the female spade at the headlight pigtail. SO, it seems to me that the problem has to be with a connection somewhere between the fuse and the A18 pin within the electrical panel. But I want to see what people's suggestions are before I pull out the panel! I should also mention that I did clean up the ground at the front left of the engine bay where the left headlight is grounded, and the fuse contacts. Finally, note that the left low beam works.

Related, but separate question: is there a headlight relay on this car? Given all the other relays, I would assume there is one, but I cannot find it on the wiring diagram. It's certainly conceivable that I'm missing it, because I'm still figuring out all the details encoded in the Porsche current flow diagrams. If so, let me know where it's represented on the diagram.

Thanks for your input!
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1981 924 Weissach Ed #187
1971 MG Midget
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Raize  



Joined: 18 Sep 2013
Posts: 131
Location: Scotland

PostPosted: Sun Apr 26, 2020 6:32 am    Post subject: Reply with quote

Your diagnosis seems correct. Do yourself a favour and relay your headlights though. It makes them so much better.
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1981 N/A daily driver with:
Headlight relays. Vacuum gauge. Cold start switch. Kill switch. Ported cylinder head, intake and 944 exhaust. Brake booster venturi delete. 53/35mm throttle body. M62 supercharger mounted but not connected
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slowcarfast  



Joined: 03 Jan 2020
Posts: 17
Location: Seattle, WA

PostPosted: Mon Apr 27, 2020 9:42 am    Post subject: Reply with quote

After doing a bunch of reading last night, I realized that this is a pretty common sort of problem, that indeed there are no headlight relays on this car (which certainly contributes to the problems), and that is it possible to get into and repair the electrical panel. I think it was on the Pelican forum where I found a thread where someone tore into the panel and fixed it (on an early 944, I think). So today I got the fuse / relay panel out of the car. Not too terrible really. Definitely would recommend taking off the steering wheel. It's dead easy and significantly eases access. The very good news is that my electrical panel looks to be in great shape generally: no corrosion and no signs of overheating either on the plugs or the pins. Even the infamous Blue Plug is clean as a whistle with no signs of overheating at D3. With the unit on the bench, it's not hard to separate the white rear panel from the front. They are glued together, so I ran a razor blade all the way around the seam and then just carefully and gradually pried off the white back panel with a stiff paint scraper. I had no idea what would be in this "black box". Very interesting to find layers of thin metal bus bars with the pins attached, separated by insulating plastic sheets. All the pins look good except for A19 (left low beam) and A18 (left high beam). Both are broken off their bus bars. So I've found the problem!

Question: how to fix this? It looks like originally the pins were perhaps riveted to the bus bars? Does anyone know if the pins are available so I could affix new ones? My other thought is, of course, to try to solder the original pins back on. Any thoughts appreciated!

And I absolutely will work on putting in relays. I did them on my MG, so I am familiar with the process. I still want to get these issues solved with the original wiring tho, because the easiest way to rig up the relays will be to use the original headlight wiring for the switching current on the relays.
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1981 924 Weissach Ed #187
1971 MG Midget
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slowcarfast  



Joined: 03 Jan 2020
Posts: 17
Location: Seattle, WA

PostPosted: Thu Apr 30, 2020 10:13 am    Post subject: Reply with quote

Well, I decided I could not reliably repair the broken pins. Better I think to just delete them, then go ahead and install relays. I realized I could simply use the good right side headlight circuits for the switching current. I'll go ahead and put in wiring for driving lights while I'm at it. At least I now have a pretty good understanding of the fuse/relay panel, and I know mine's in good shape other than 2 broken pins ... assuming I got it back together properly. So I'll wrap up this thread, which I know has been followed avidly. And I'll let you all know if/when I have questions about putting in the relays.
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1981 924 Weissach Ed #187
1971 MG Midget
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slowcarfast  



Joined: 03 Jan 2020
Posts: 17
Location: Seattle, WA

PostPosted: Mon Jun 01, 2020 3:39 am    Post subject: Reply with quote

Relays done; now have low and high beams, left and right! Also put in the wiring for driving lights, which I'll install soon. Everything else also seems to work, so it looks like I managed to get the electrical panel back together without mucking anything up in there.

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1981 924 Weissach Ed #187
1971 MG Midget
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TJC  



Joined: 04 Apr 2010
Posts: 751
Location: Central-ish Arizona, USA

PostPosted: Mon Jun 01, 2020 11:54 pm    Post subject: Reply with quote

Nicely done. Sometimes it's best to abandon the old stuff and "originality" for the reliable and safe if you want to use the car.
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'95 BMW 318i/5 ..."Pearl"
'80 Porsche 924 Turbo..."Pogo"
'81 Porsche 924 Turbo...Parting!
'87 Porsche 944 NA... "Liebchen"
'02 Porsche Boxster..."Sunbeam"

Still on the Prowl!

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