WallyP

Perhaps I didn't say this clearly enough...

"Yes, that is a misprint. Look in J9, and you will see a box labeled O31, which is where the mislabeled box is located. It shows the brown wire going to a welded connection point labeled 1, and from there to ground.

All brown wires are ground or earth.
All brown/with a stripe are switched grounds.

The size is because the rear defroster pulls some serious amps... "

The wiring diagram shows the brown wire going to a chassis ground.

Hooking a brown wire (ground) to a black wire (power) on a 928 will lead to a blown fuse if you are really lucky, a melted wire harness if you are moderately lucky, and a toasty hulk if you are really unlucky.

Mrmerlin

I dont do well with describing words a picture will provide much more value

yardpro

wally.

you were very clear.. i must not be conveying the question clearly...

i totally understand that the big brown is a ground...

my question is where the end with the female plug hooks to?

the wire harness that comes up from the pillar into the hatch roof has no large brown wire to connect it to...

i have just up;loaded some pics from my phone to my pc..

the first pic is what i found when the light fell out...you can see the melted wires. the green, white and brown sheathed wires go to the back light (they tie in tp thr top hatch light)

the second pic is the connector after the panel was removed.. you can see the cooked red wire and the brown wire to the left of it... the large black with the blue butsplice was NOT connected to anything

the third pic is the brown and black i have been asking about.. they come yup from the window heater elements into the top of the hatch

the last pic shows the ends of these two wires..
I know the black from the connector hooks to this black, but where does the brown connect?

FYI.. the butt splices are marine grade heat shrink connectors... VERY high quality connectors, that form an airtight seal... also VERY expensive

yardpro

a few more for clarification

the one pic shows the two red wired going down the side of the hatch to the passenger side defroster element.. the black wire is actually the white, green and white that connect to the rear hatch light.. they are in a black sheath.

the second pic is where the wires come up from the pillar, and into the hatch roof,, they come out through the plastic curved piece.

yardpro

any ideas what to connect the brown wire to to get it to the correct ground location?

Alan

Well you could just screw it to the hatch sheet metal - that is grounded - like the rest of the body.

You should have a brown wire running through the hatch to roof connection - that is what you should really use - its on pin 3 of the connector.

Alan

yardpro

the wire on pin 3 is MUCH smaller gauge than the big one coming from the heater... I am concerned about the potential amperage cooking the wire...

Landseer

Using wiring diagram, label ( you can buy the sticky lables at home depot or lowes ) and trace every wire by color, diameter and start/end point. Peel away the right side carpets if needed and pull the CE panel.

Diagram it on a sheet of paper.

Don't connect anything else / too much cobbling has occurred on that harness already.

Replace all wires with the right wire color and diameter. All those crimps are trash, including the waterproof ones.

You want it right, do it right.

That's the only way to do it right.


Your pictures kinda suck for giving good reference to us playing at home. I think I see a black/white wire with AWG printed on it. Its trash too. Somebody tried to avoid the $500 of harness costs to rewire a completely melted harness using cobble. Happens on 25 year old cars.

The HVAC fan and the defroster and mirror heater circuits on these cars are notorious for scorching all the way back to the CE panel, including the rear spaghetti of wires and can cross into other wires. So, its mandatory to trace it all.

yardpro

thanks for the advise.

chris.
I appreciate your advise..
just to clear the air... the awg is history.. PO did that job...
there is only one splice now between the connector the existing wires.
AS for the connectors, you must not be familiar with ABYC marine electrical connectors, and their crimps..They are by far the best connector out there.. they have a special, rather expensive crimp tool requires to properly crimp the connector, then have an adhesive that is activated when the fitting is heated.. The marine industry has MUCH higher standards for electrical component connections than the automotive industry...if you have an electrical fire in your car, you pull over and get out... you have an electrical fire 25 miles off shore... shark bait...

i removed the connector, heated the pins and removed the wires and solder, then re soldered new appropriate wires into the pins... no i did not have the correct colors, but i do have a legend that will be secured to the connector to facilitate any future work....

Landseer

I was reacting to my last review of the wiring pictures , trying to match against my car and figure out what was out of place. After that excercise, its clear I can't help from here, other than regurgitate the "trace and eyeball" method, nothing short of that has worked for me once discovering a melt. Had a defroster wire just barely melted into the LH or EZF relay power feed wire on our 85 that haunted me for weeks.

I always have problems not having appropriate wire and brass terminals. Availability is better via internet, but still costly and somewhat obscure. Eagle Day has the parts but at a high price. I want to order a slew of that stuff. Right now, am robbing from old 944 and 928 harnesses. Sounds like I need to investigate marine.

I'm generally using the metal pieces only from inside those plastic crimps, soldering a butt splice with them, then applying a higher quality double wall, adhesive lined heat shrink.

Sounds like you are on the right track.

yardpro

the masrine grade are the way to go...The only issue is that you need a special crimp tool to properly crimp them. For a marine crimp to pass, it has to hold a specific amount of weight.. they test them by hanging weights on a wire with a butt splice.. if the crimp fails... it is not approved.

Only issue is the cost. A blue butt splice is about $3.00 per fitting.. the proper tool to splice any of the fittings is $60-$80.00.

I am struggling with the proper wire color/size..
I will in the future go back and replace with the proper colors.. I was just trying to get everything working just for the sake of having everything work..

I guess i need to see if i can entice someone to pull the top hatch cover (the one with the rear sun visors) and snap a pic of where the big brown wire actually runs after the female connector.

BC

Yard -

Essentially, there is one ot two main ground wires that go into the plug on the passenger side B pillar near where the speaker goes on later cars. That flat-wired loom that goes all the way up to the hatch area, and separates into a few different areas:

1) The defroster (or as I like to call it "Timer based cockpit fire system") (I remove them)
2) The rear third brake light
3) The Light at the upper part of the hatch behind the driver's head
4) The light at the bottom of the hatch where the tools are.

The wire I THINK you are talking about from your pictures is the "power" or 12V for the hatch light behind the driver's head. That then is normall spilced by the factory to run down the side of the hatch to the other light. There is a larger ground wire thht goes into that crimp, and comes out as three grounds - one to the backup lamp, and the others to the lights.

Honestly, Porsche did not seem to think very clearly about what happens to wires and crimps and thin coverings over important wires when being bashed and bounced about near uncovered metal body parts in a sports car for 25 years. Whenever I get these car (I have had 8 now) unless these faulty areas are in pefectlty good order, I remove many of the looms simply because I have no use for them and I need wires to be tightly crimped, packaged properly, and tied down properly or I can't think.

The unbelievably stupid **** that happens to these cars over thed decades is not only because the prices for new looms and stock wiring is outrageous - its simply because most people do not understand or enjoy wiring, and are too freaking lazy to look up what something is intended to do in the stock wiring diagrams. Ocassionally it does not help with the published diagrams are incorrect and Porsche simply never cared to correct glaring mistakes.

***
You may also be running into the issue depending on your year that there is an additional loom that runs down the hatch body panels which plugs into the hatch lock (male part) for the central locking system.

yardpro

thanks BC.
i have all the wires sorted out except the large gauge brown wire.

It is defianately a ground for the lower defroster psnel. Wally and I have discussed the wiring diagram issue.. mispring on where it goes...

I have hooked everything back up and ordered a new light, as mine is broken. ( the plastic that holds the steel spring loaded ball is broken.