frod

@mazdaverx7 my short was coming from the headlight motor. It melted the headlight switch and the wax around the other cables.

@Tiger03447 thank you for the response. I’ll search for the wiring diagram and plot it.

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orig944

The early cars have numerous unfused circuit paths. For example, the fog light relay (as Tiger unfortunately found out) has no fuse. That fuse is between the relay and the fog lights when it could just as easily been before the relay. Just dumb. The fuel pump / DME relay is unfused, along with the DME itself, the fuel injectors, and the instruments. Plus there are more.

They must have figured this out eventually, since the remodel has about double the number of fuses. But, I won't vouch for complete fuse protection on the new one either.

orig944

Yeah, the headlight switch too.

Tiger03447

I just ordered the wire last week. Money at my house has been pretty short lately. I’m in the process of talking with a German company that makes solid state power distribution panels . No fuses,no relays. All mosfet type transistors stuff. I’m certainly no EE guy, but I don’t want a recurrence of the previous event. I have no idea as to the price or if they will even talk to me in a serious manner. Thought it might be a better way to fly. Time will tell. I’ll keep the loop open. Also considering installing a later model fuse panel over in the glove box space. Just a mega job of extending the wiring from the firewall to the glove box area. Front and rear harnesses seem OK. Just the center section is FUBAR. Thanks .😀

harveyf

Rich, I forgot to mention them when we talked but "fused links" are a very cost effective way to add overlead protection to any circuit. Yes, they will get destroyed if there is an actual overload but that certainly beats the alternatives!

Chalt

So does this mean the DME is vulnerable to a short and it could be fried since it is unfused?

Chalt

In which scenarios would a fused link be better than an inline fuse?

Chalt

Researching, I found a wiring supplier for vintage hot rods. I downloaded their catalog (Ron Francis Wiring). https://www.ronfrancis.com/ (I am not affiliated) On their website, it says request a catalog, and you can download the pdf.

Now, I know we aren't working on hot rods/american muscle, but catalogs like this are often helpful, TO ME, anyway (sorry for yelling). The way they are helpful is that they give me:

1. They identify terminology, like a menu at Denny's, you maybe can't read (not you, but someone), but you can point to the pancakes and say I want that. How can you search the internet for a pancake if you don't know it's called a pancake? Catalogs can help with that.
2. You can get ideas that may cross over you your application.
3. You may actually be able to buy from that catalog.

Tiger03447

Yeah, I’ve been down the burned up headlight motor harness gig as well. AND the headlight switch melted too. That one was my fault. Actually when the relay stuck I was trying to get the headlights to retract and the fog lights were on. Apparently they were on “too good”. I haven’t received the wire yet, probably be in after the holiday. AFAIK, there isn’t much difference between a fusible link and a fuse itself. It takes up less space in the harness, because you don’t need a fuse holder and it can be spliced right into the wire. Just more stuff to deal with when it blows and needs to be replaced. TIA guys😀

harveyf

@Chalt I haven't much background on fused links but would say off the top of my head that they are more durable in a wet environment. Most of the in-line fuse holders that I've run across don't look like they would hold up say inside the engine compartment. It is interesting that a Porsche electrical design team chose to tolerate certain wiring paths, as described inside this thread, without any overload protection. Since they worked for Porsche, I'm going to say they had their reasons but it would be interesting to know what those reasons were. That said, I can't recall any car I've owned where the main power feeds from the battery and the alternator were fused.

Tiger03447

I used to have a Grumman truck that had a fusible link mounted right on the battery. I started the engine, then turned on the headlights. Blew the link. Engine died and left me stranded. Had to call a flatbed and take it to the dealer to fix it. I don’t think that I’ve ever seen a fused battery to starter or alternator wiring harness either. Hmmm.

Tiger03447

Well, since my last post, I have received my wire, and an EBay later fuse/relay panel with all of the smaller plugs in the back. (14?). I am considering cutting the wires going through the firewall, putting in Deutsch connectors on both sides of the incoming wires, adding new 16 ga wire and rethreading it back through the firewall. Then I will take the new wire behind the HVAC unit and put a later fuse/ relay panel where the glove box used to be, only retaining the door, to keep the panel from view. At least this is my plan, which will, most likely have to be changed multiple times before this mess is sorted out totally. Thanks for the rant😀!

Chalt

Show us pictures as you progress.

Tiger03447

I will try. But with the hot weather and no A/C in the garage, it’s a cooker in there even at night. Hope to get the a/c problem fixed first, and SOON!😀