Stock wiring questions

by builtnotbought Thu Jan 28, 2016 3:53 pm

I have a questions about stock 74 elco wiring. I will appreciate any help.
I'm rebuilding car and I decided to leave stock harnesses. I checked all old wires, cut broken and repair somewhere, lengthened generator, wiper motor and heater harnesses to hide them a little. I made new "+" and "-" Batt cables from welding cable, installed circuit breaker on "-" wire near Batt. Ran new "-" wires from circuit breaker to frame, from frame to engine block, from frame to body using the same welding cable.

When the car was running several years ago I had a curios case when on the turn of the road the main "+" wire from Batt hit the header and all car turned off. No smoke no smell only everything turned off. Then no response on ignition. Wire was isolated again and the next day car became alive as nothing happened. Now I guess it was a temperature fuse that recovered aften the case.

My questions are -

1. Where is the main temperature fuse located in the stock wiring? How does it look like?
2. Is temperature fuse factory on 73-77 or do I have aftermarket one?
3. Should I strengthen stock wiring with main Mega fuse and where it should be better located in harness?

As I understand starter and Gen harnesses are not protected with fuses in stock wiring, am I right?

Thank you for help!

by ant7377 Thu Jan 28, 2016 10:43 pm

Sounds like you had a bad connection at the starter or on the battery,there is no Mega fuse. The starter wire does have a fusable link at the end of the wire on the big terminal. A fusable link is designed to melt if there was ever a short at that wire as a fuse would.

by 74 beast Fri Jan 29, 2016 1:37 am

Chech with painless wiring bet you can get front harness and just start new

by builtnotbought Fri Jan 29, 2016 3:01 am

74 beast wrote:Chech with painless wiring bet you can get front harness and just start new

New wiring is always great but now I'm not ready to buy it.

ant7377 wrote:Sounds like you had a bad connection at the starter or on the battery,there is no Mega fuse. The starter wire does have a fusable link at the end of the wire on the big terminal. A fusable link is designed to melt if there was ever a short at that wire as a fuse would.

May be it had a fusible link on the end before short, service didn't tell me anything. When I disassemble wiring it had usual straight wires coming to starter.

So now I have new straight wires from Batt to starter big terminal, and 2 other wires connected to big and small starter terminals thats going to Generator and Ignition, and new Ground wire with mechanical switch from Batt, all of them without fusible links.

What wires from 4 mentioned above I need to protect with fusible links/fuses?
Can you prompt what Ga wires are coming to starter terminals in stock wiring?

Thank you, sorry for fool questions but I don't have lots of knowledge in wiring.

by ant7377 Fri Jan 29, 2016 7:04 am

The only wire on the starter that gets a fusible link is the one from the car to the big terminal. Im not sure what gauge though. Someone here will know.

by builtnotbought Fri Jan 29, 2016 7:22 am

ant7377 wrote:The only wire on the starter that gets a fusible link is the one from the car to the big terminal. Im not sure what gauge though. Someone here will know.

Thank you

Found here on forum that red wire going from Big starter terminal to junction box on the firewall is 10ga factory and it must be protected with 14ga fusible link.
Only this wire must have fusible link inline.

Somebody please confirm ga.

Thank you

by ant7377 Fri Jan 29, 2016 7:58 am

Yes thats the one. If it blows it makes a lot of smoke.

by thatfnthing Fri Jan 29, 2016 10:11 am

demid wrote:
ant7377 wrote:Sounds like you had a bad connection at the starter or on the battery,there is no Mega fuse. The starter wire does have a fusable link at the end of the wire on the big terminal. A fusable link is designed to melt if there was ever a short at that wire as a fuse would.
May be it had a fusible link on the end before short, service didn't tell me anything. When I disassemble wiring it had usual straight wires coming to starter.

So now I have new straight wires from Batt to starter big terminal, and 2 other wires connected to big and small starter terminals thats going to Generator and Ignition, and new Ground wire with mechanical switch from Batt, all of them without fusible links.

What wires from 4 mentioned above I need to protect with fusible links/fuses?
Can you prompt what Ga wires are coming to starter terminals in stock wiring?

Thank you, sorry for fool questions but I don't have lots of knowledge in wiring.

The car would have originally come with a fusible link (FL) on the wire from the small starter terminal to the horn relay -- this is the main feed for most of the electrical system in the car. It sounds like someone removed it from yours in the past. It's easy to replace -- a FL is simply an ordinary wire that is 4 sizes smaller than the wire you are trying to protect. So 14ga for a 10ga wire, 16ga for a 12ga wire, etc. It's job is to melt in case a short happens between the starter and the fusebox, since only the circuits AFTER the fusebox are protected by the fuses. If a short happened before the fusebox, there would be nothing to stop it and it could burn your car to the ground. So the FL melts and breaks the circuit to save all the rest of the wiring. Here's a photo showing a FL protecting the main red wire (top) -- the ring terminal goes on the starter terminal:

Stock wiring questions Fl10

Also, once you get to the horn relay next to the brake booster, you will find a lot of other FL's coming off of it -- this is where most of the car's circuits branch out from, and there still is no fuse protection, so a bunch of FL's are used.

Hope that helps!

by ant7377 Fri Jan 29, 2016 6:21 pm

Is it like that on a 74? I thought that was only 73? I know there is differences.

by thatfnthing Fri Jan 29, 2016 6:35 pm

Could be some differences, but it should be pretty close. I know the ignition is wired different from points to HEI. I only have full diagrams for 73, but there have other threads where it turned out that the 73 wiring was the same in 77.

In any event, the rule of thumb still stands -- if a circuit has no fuse protection, it should have a FL. The exceptions are obviously the main batt-to-starter feed and the main alternator feed, and I believe HEI did not have one because the much smaller diameter wire can induce resistance that will negatively impact HEI performance. Same reason you don't use the old points resistor wire to feed an HEI upgrade.

by ant7377 Sat Jan 30, 2016 11:51 am

The old points resistance wire. Where does it go? I have a petronix in my 73 to eliminate the points and I took of that wire but is hot I have it all taped up but I dont like it under there hot like that. Does it go to the small terminal on the starter?

by builtnotbought Sat Jan 30, 2016 5:39 pm

thatfnthing wrote:
demid wrote:
ant7377 wrote:Sounds like you had a bad connection at the starter or on the battery,there is no Mega fuse. The starter wire does have a fusable link at the end of the wire on the big terminal. A fusable link is designed to melt if there was ever a short at that wire as a fuse would.
May be it had a fusible link on the end before short, service didn't tell me anything. When I disassemble wiring it had usual straight wires coming to starter.

So now I have new straight wires from Batt to starter big terminal, and 2 other wires connected to big and small starter terminals thats going to Generator and Ignition, and new Ground wire with mechanical switch from Batt, all of them without fusible links.

What wires from 4 mentioned above I need to protect with fusible links/fuses?
Can you prompt what Ga wires are coming to starter terminals in stock wiring?

Thank you, sorry for fool questions but I don't have lots of knowledge in wiring.

The car would have originally come with a fusible link (FL) on the wire from the small starter terminal to the horn relay -- this is the main feed for most of the electrical system in the car. It sounds like someone removed it from yours in the past. It's easy to replace -- a FL is simply an ordinary wire that is 4 sizes smaller than the wire you are trying to protect. So 14ga for a 10ga wire, 16ga for a 12ga wire, etc. It's job is to melt in case a short happens between the starter and the fusebox, since only the circuits AFTER the fusebox are protected by the fuses. If a short happened before the fusebox, there would be nothing to stop it and it could burn your car to the ground. So the FL melts and breaks the circuit to save all the rest of the wiring. Here's a photo showing a FL protecting the main red wire (top) -- the ring terminal goes on the starter terminal:

Also, once you get to the horn relay next to the brake booster, you will find a lot of other FL's coming off of it -- this is where most of the car's circuits branch out from, and there still is no fuse protection, so a bunch of FL's are used.

Hope that helps!

Thank you for the info but you got me confused at all with starter terminals. I checked today all these wires with tester and draw a scheme of my wiring.
Stock wiring questions Oaia_213

So I need to put FL only at wire No.1 from big starter terminal to junction unit. Or the wire from small starter terminal that goes to cluster need FL too?
And what do you mean "horn relay" ?

Sorry for crappy scheme.
Thank you

by thatfnthing Sat Jan 30, 2016 7:15 pm

ant7377 wrote:The old points resistance wire. Where does it go? I have a petronix in my 73 to eliminate the points and I took of that wire but is hot I have it all taped up but I dont like it under there hot like that. Does it go to the small terminal on the starter?

Going back to look at my diagrams (my wiring is long gone) The YEL wire from the R terminal on the starter is ordinary wire. The 20ga BLK wire with PNK print from there is the resistance wire (1.35 ohms for 8 cyl), and runs back to the bulkhead connector. On the inside of the cabin, it becomes a 12ga PNK which runs back the ignition switch.

Short answer -- you should be able to remove both the yellow and black wires if you have the Pertonix wired independently.

by thatfnthing Sat Jan 30, 2016 11:46 pm

demid wrote:Thank you for the info but you got me confused at all with starter terminals. I checked today all these wires with tester and draw a scheme of my wiring.

So I need to put FL only at wire No.1 from big starter terminal to junction unit. Or the wire from small starter terminal that goes to cluster need FL too?
And what do you mean "horn relay" ?

Sorry for crappy scheme.
Thank you

Not crappy at all! In fact, very helpful.

Your 'junction box' is actually a relay used to power the car's horn. However, the factory also used it to split power off from the main feed (#1) to a bunch of other circuits, so it actually does act like a junction box too.

So #1 is the main feed from the starter to the rest of the electrical system via the 'junction box', and along the way splices with the feed from the alternator like in your drawing. The alternator actually powers the car's systems via this circuit when the car is running.

#2 should be a 16ga red wire that runs from the junction box to the alternator (like in your diagram) -- the alternator uses it to measure the current in the system in order to know how much electricity to put out. It has a 20ga FL of its own on the junction box end.

According to the diagram, #3 could be any of a couple different wires that lead to the bulkhead connector below -- each will have a FL protecting (again on the junction box end), and its function will depend on what the wire color is and what terminal on the connector it goes to.

FL HERE: Yes, a 14ga FL should go right there at the starter end to protect the #1 red 10ga wire.

OR HERE TOO: I'm guessing this is a purple wire, yes? If so, it is the feed from the ignition switch to start the car, and should NOT have a FL.

Also, keep in mind the bulkhead connector where #3 goes is not the fuse box itself. It's just a connector for the wires to pass through the firewall. The fuse box actually mounts on top of it. If you unbolt the fuse box, you'll see some of the wires that come through go to the fuse box and some go other places inside the car.

Hope that helps!

by builtnotbought Sun Jan 31, 2016 5:33 pm

Yes that helps a lot, thank you!

thatfnthing wrote:
Your 'junction box' is actually a relay used to power the car's horn. However, the factory also used it to split power off from the main feed (#1) to a bunch of other circuits, so it actually does act like a junction box too.

it's cool, what a curious fact

thatfnthing wrote:
So #1 is the main feed from the starter to the rest of the electrical system via the 'junction box', and along the way splices with the feed from the alternator like in your drawing. The alternator actually powers the car's systems via this circuit when the car is running.

#2 should be a 16ga red wire that runs from the junction box to the alternator (like in your diagram) -- the alternator uses it to measure the current in the system in order to know how much electricity to put out. It has a 20ga FL of its own on the junction box end.

Yes #2 alternator wire is red and it has a strange rubber/plastic transparent barrel as on attached photo before eyelet. Is it FL you talking about?
I repaired mine because eyelet wire got broken where it's connected to the barrel. I think I need to buy new one. Are these barrel type FL available now somewhere? Can't google them.
Stock wiring questions 2010-010

thatfnthing wrote:
According to the diagram, #3 could be any of a couple different wires that lead to the bulkhead connector below -- each will have a FL protecting (again on the junction box end), and its function will depend on what the wire color is and what terminal on the connector it goes to.

Wire #3 as I can see is factory on my car with no repairements, simple wire with eyelet on the junction box end. It goes to the bulkhead's left lower corner. Don't know if the part of the wire that is under hood is FL but I think I will not touch it and change to FL.

thatfnthing wrote:
FL HERE: Yes, a 14ga FL should go right there at the starter end to protect the #1 red 10ga wire.

OR HERE TOO: I'm guessing this is a purple wire, yes? If so, it is the feed from the ignition switch to start the car, and should NOT have a FL.

Yes I think it's purple and it goes right to the bulkhead, and tester showed the other end of this wire is on the steering column long wire jack controlled with ignition key.

thatfnthing wrote:
Also, keep in mind the bulkhead connector where #3 goes is not the fuse box itself. It's just a connector for the wires to pass through the firewall. The fuse box actually mounts on top of it. If you unbolt the fuse box, you'll see some of the wires that come through go to the fuse box and some go other places inside the car.

Exactly! But I couldn't be sure that it is FL on the junction box end.

Thank you

by thatfnthing Sun Jan 31, 2016 6:02 pm

Glad I could help!

demid wrote:
thatfnthing wrote:
So #1 is the main feed from the starter to the rest of the electrical system via the 'junction box', and along the way splices with the feed from the alternator like in your drawing. The alternator actually powers the car's systems via this circuit when the car is running.

#2 should be a 16ga red wire that runs from the junction box to the alternator (like in your diagram) -- the alternator uses it to measure the current in the system in order to know how much electricity to put out. It has a 20ga FL of its own on the junction box end.
Yes #2 alternator wire is red and it has a strange rubber/plastic transparent barrel as on attached photo before eyelet. Is it FL you talking about?
I repaired mine because eyelet wire got broken where it's connected to the barrel. I think I need to buy new one. Are these barrel type FL available now somewhere? Can't google them.

Is that the alternator end? Yes, that sure looks like a FL. Maybe they did it in later years (which would make sense if a short should happen on the alternator end of the wire), but the 73 diagram only shows a FL at the starter end of that circuit. The plastic barrel doesn't really serve a purpose, it's simply where the two different size wires are bonded together. If you pick up a 14ga FL, it will come with some kind of splice like in the picture I showed earlier. Just cut the old one off past the plastic barrel and attach the new one to the red wire.

demid wrote:
Wire #3 as I can see is factory on my car with no repairements, simple wire with eyelet on the junction box end. It goes to the bulkhead's left lower corner. Don't know if the part of the wire that is under hood is FL but I think I will not touch it and change to FL.

If it's never been touched, I'd leave it alone unless you're having a problem of some kind.

demid wrote:
Yes I think it's purple and it goes right to the bulkhead, and tester showed the other end of this wire is on the steering column long wire jack controlled with ignition key.

The purple wire goes back the bulkhead connector. Inside the cabin it runs to the neutral safety switch on the base of the steering column. From there it becomes purple with a white stripe and runs back to the ignition switch.

by builtnotbought Mon Feb 01, 2016 6:28 am

thatfnthing wrote:
Is that the alternator end? Yes, that sure looks like a FL. Maybe they did it in later years (which would make sense if a short should happen on the alternator end of the wire), but the 73 diagram only shows a FL at the starter end of that circuit. The plastic barrel doesn't really serve a purpose, it's simply where the two different size wires are bonded together. If you pick up a 14ga FL, it will come with some kind of splice like in the picture I showed earlier. Just cut the old one off past the plastic barrel and attach the new one to the red wire.

Yes, I have the same type alternator end as on photo. I think there is a metal stripe inside the barrel and wires on both sides connected are the same size.

thatfnthing wrote:
If it's never been touched, I'd leave it alone unless you're having a problem of some kind.

ok

thatfnthing wrote:
The purple wire goes back the bulkhead connector. Inside the cabin it runs to the neutral safety switch on the base of the steering column. From there it becomes purple with a white stripe and runs back to the ignition switch.

Got it, thank you!

I made some more photos of strange jacks and connectors in the harness, I will post them later. May be somebody will recognize something.

by thatfnthing Mon Feb 01, 2016 10:48 am

demid wrote:Yes, I have the same type alternator end as on photo. I think there is a metal stripe inside the barrel and wires on both sides connected are the same size.

They might be the same size on the outside, but not the actual wires inside. The FL will just have thicker insulation.

demid wrote:
I made some more photos of strange jacks and connectors in the harness, I will post them later. May be somebody will recognize something.

I love a good puzzle. Smile

by builtnotbought Mon Feb 01, 2016 3:22 pm

thatfnthing wrote:
demid wrote:Yes, I have the same type alternator end as on photo. I think there is a metal stripe inside the barrel and wires on both sides connected are the same size.

They might be the same size on the outside, but not the actual wires inside. The FL will just have thicker insulation.

demid wrote:
I made some more photos of strange jacks and connectors in the harness, I will post them later. May be somebody will recognize something.

I love a good puzzle.

I meant wires are the same size but metal stripe inside the barrel is thinner and it breaks under heavy load.

Ok, let's continue Very Happy

I have these strange things in harness

1. Orange one with a cap. Cap is off. I guess it's smth like stock under hood light connector, correct me please if I'm wrong.
Stock wiring questions Oaia_311

2. Two plastic boxes like modern fuses holders, green and black.
Stock wiring questions Oaia_410

3. Yellow box. I guess it's a relay for something
Stock wiring questions Oaia_510

4. White holder with something yellow glued in.
Stock wiring questions Oaia_113

5. Where do these two Ground stripes run from firewall? May be to wiper motor and...
Stock wiring questions Oaia_115

Thank everybody for any suggestions!

by ant7377 Mon Feb 01, 2016 6:45 pm

The green thing is the key buzzer. The 2 grounds in your hand one goes to the hood and one to the back of cylinder head yellow thing is a relay for something. The orange thing I have never seen on one of these cars same with the white thing which might just be the angle the picture is at.

by Mcarlo77 Tue Feb 02, 2016 1:31 am

Orange connector block on engine side firewall is where the original Seat Belt Interlock Relay was plugged into. This p.i.t.a. feature was unique to '74 and early '75's...and, was usually over-ridden by bypassing it, removing the relay and installing a cap over it.

The white connector may be part of the disconnected Seat Interlock wiring to the passenger seat; although seems like the ones I've seen were black. Maybe somebody epoxied the inner connectors to seal them?

by builtnotbought Tue Feb 02, 2016 3:05 am

ant7377 wrote:The green thing is the key buzzer.

This thing must make noise when the key is turned to ingnition ON and drivers door is opened, Does it?

ant7377 wrote:
The 2 grounds in your hand one goes to the hood and one to the back of cylinder head yellow thing is a relay for something.

Got it! Thank you

Mcarlo77 wrote:Orange connector block on engine side firewall is where the original Seat Belt Interlock Relay was plugged into. This p.i.t.a. feature was unique to '74 and early '75's...and, was usually over-ridden by bypassing it, removing the relay and installing a cap over it.

My car has a cap on it. And I noticed that my belt spools under seat have connectors for some wires. But I thought they are for belt buzzer if belts are not locked.
What does p.i.t.a letters mean?
What was this system "Seat Belt Interlock Relay" made for?

I googled a little, as I understand, this system allows car to start the engine only when the belts are locked. If not IGN key will not affect starter at all.

Mcarlo77 wrote:
The white connector may be part of the disconnected Seat Interlock wiring to the passenger seat; although seems like the ones I've seen were black. Maybe somebody epoxied the inner connectors to seal them?

It looks like factory epoxied.

by ant7377 Tue Feb 02, 2016 7:31 am

I never had a 74 thats why I never saw it. The buzzer is supposed to make noise,yes.

by Mcarlo77 Tue Feb 02, 2016 10:37 am

P.i.t.a. (pain in the A$$). And yes...the Interlock System would not allow the engine to start unless the belts were buckled (there was no buzzer). Particularly annoying was the placing of something on the passenger seat (like a bag of groceries) and not being able to start the car unless you belted it in...lol! Complaints from consumers became so great that this hare-brained gov't mandate was rescinded.

Is that white connector detachable from the black portion? If so, I'm guessing it's another cap of sorts for what I still think is the harness that would feed the passenger side seat belt interlock system.

by thatfnthing Tue Feb 02, 2016 11:59 am

Most of that stuff wasn't on my 73, so those were head scratchers for me... scratch

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