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928 Indicator Lights & Hazard Switch Wire Melted

 
Old 01-24-2015, 09:02 AM
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desperateaudio
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Default 928 Indicator Lights & Hazard Switch Wire Melted

Hey guys I am new to the forum. I have owed several porsche's in my life but at the present time I owe a 1986 928s and I am hoping you guys can help me with the following issue I am having.

When I purchased the car she had been sitting for a while with only 3 owners (me being the 3rd) and 54K in milesshe is in very good condition but has many of the gremilns that come up on the 928's that have been left sitting. I have fixed all of them but one and the issue is as follows:

I pulled the CE panel out to do a cleaning as normal and here is what I found: (For reference I also have the POD completely removed from the car so I have direct access to all switch bases)

1. I took notice that the "B" plug has a wire at pin "15" that got so hot from the back of the plug heading into the wiring harness that it melted the rubber covering right off that wire all the way to the harness up under the dash.

2. Also I noticed that on the back of the CE Panel where the "B" Plug would attach into the CE Panel there is a jumper wire from pin "15" to Pin "14" of the "B" Plug that is also had it's rubber partially melted off it.

3. The wire is black and is a power supply when the ignition key is in position 2 and start. The wire originally starts it's life at the ignition switch Terminal 15, goes to the CE Panel - "B" Plug at Pin "12" and jumps from there to Pin's "13", "14" & "15".

4. From Pin "15" it exits the back of the plug, goes up into the harness under the dash and according to the schematic I have it comes straight to Terminal 15 of the Hazard Switch.

See this link which is Page 4 and you go to grid G5:

http://www.manualslib.com/manual/392...?page=4#manual


5. I have checked the continuity of the wire between the ignition switch and the "B" Plug Pin "12" and all is good. I have checked the continuity of the jumper wires from the "B" Plug Pin "12" all the way to Pin "15" of the "B" Plug and all is good with the wire.

6. I checked the continuity of the wire in question from the "B" Plug Pin "15" to the bare copper where it disappears into the harness under the dash and I have continuity but when I check it from Pin "15" back to the Hazard Switch Base at Terminal 15 I have no continuity which seems to me that the wire in question must have burned through and severed itself up insde the harness. Would this seem correct to you folks based on the attached schematic?

7. There are NO burned or melted wires at the Hazard Switch Base.



FOR REFERENCE: These are the rest of the items pulling power on that line from Terminal 15 of the ignition switch to the "B" Plug Pin "12"

"B" Plug Pin # 12 feeds power to Pins "13", "14" & "15" but it also feeds the 7.5A fuse for the AC which then travels back out of the CE PANEL via "G" Plug.

"B" Plug Pin # 13 goes to the back window heater switch.

"B" Plug Pin # 14 goes to the kick down switch.


This whole issues is centered around the Hazard and Individual blinkers for all 4 corners of the car. Now here is the problem. The Hazards work but the individual blinkers do not. If you look at the schematic page noted above you will see that when you push the Hazard Switch in to make the hazards works you get power from Terminal 30 which is direct battery power. When the switch is open which is the default you get turn signal power from Terminal 15 via the "B" Plug Pin "15".

I believe the fix is to replace the burned wire from the "B" Plug at the CE Panel to the back of the hazard switch and then my blinkers should work.

What do you folks think?

Also what the heck could have caused this to happen? Nothing else is at all messed up in the car. The car has not been hacked in any way it is all original. No water from what I can tell. I find it very odd so any help you guys can offer would be greatly appreciated.

Thx in advance for all your help,

A
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Old 01-25-2015, 02:53 AM
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My initial thought is, The signal switch is bad on the column, other issues may be involved.
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Old 01-25-2015, 06:13 AM
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Ok thx that is interesting as I see those as just switches... so u are thinking a dead short somewhere in the switch? If there a way to test the switch?

Also what are your thoughts on abandoning the melted wire and pulling another or do you think I should cut the harness wrap and find the end?

Thx again
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Old 01-25-2015, 11:40 AM
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what most probably happened was that someone was removing the pod switches with the battery still connected,
and the switches were hanging out of the pod.
Then the turn signal switch was actuated or the key was turned on ,
and the headlamp or hazard or foglamp switch grounded out on the pod housing ,
(you will notice its made of aluminum.)
( you will also notice that there are metal parts that are exposed on the sides of the barrel switches)
This in turn fried the wire to the CE panel.

To fix it carefully remove the melted wire and examine any other wires that may have gotten damaged,
if your lucky you will only have to replace one wire from a switch to the CE panel,
so take your time,
keep the battery disconnected while working on the electrical system.

Dont ask me how I know this... Hard won experience
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Old 01-25-2015, 12:43 PM
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Sounds good. All battery power has been disconnected for weeks. I must say when I took the pod off it looked like it was the 1st time anyone had touched it. Also I have examined every switch in depth and no arching, grounding melted wire at switch head, nothing. They all look untouched. Will cut back tape wrapping harness today until I find the end of the melted wire.

Thx
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Old 01-25-2015, 01:42 PM
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What you propose makes sense - the function is as you describe.

However that the wire melted means something was wrong, and may still be wrong. The (15) wire to B15 and the (30) wire to A15 are not fused - anything shorting on these or downstream will just burn up (as here). Stan may be right about cause - but I'd do some checks first.

The hazard switch connects either (15) normal or (30) hazard to the flasher pin 49 to power the flasher unit. The hazard switch active also connects both indicator feeds together and to Flasher pin 49a - this causes all the indicators to flash. This exercises almost all of the flasher functions for both sides.

For the wire on pin B15 to burn up one of the turn switch connections for each side (L or R) must have shorted to ground - and it needs to be a path that doesn't exist when only the hazard is engaged. Only the combination switch fits this scenario.

2 options:

Take the combo switch out (remove steering wheel etc) and test it to see there is never any connectivity to ground (including the case) on L & R in any position.

or (easier)

Before you replace the B15 wire - use a jumper instead with an inline fuse of 5A - and see if it works with that in L & R column switch modes - to be sure you don't still have a short...

BTW - did you move the indicator stalk into L & R positions while the hazards were on? I would NOT recommend you do this as a test - since it could provoke the same kind of short on the (30) wire... But if you have already done this with no ill effects it would suggest the short is no longer there. I'd still go with option 2 above to be safe


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Old 01-25-2015, 02:27 PM
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Thx Alan,

No I did not move the stalk while the hazard switch was engaged and due to normal copper corrosion you can see the melting took place a very long time ago as the bare wire has turned green.

So I already have the pod out and combo switch is right there so my question is am I to understand that none of the pins in the combo switch should ground to the case? Therefore only being a switching conduit to the required circuit correct?

Thanks

Anthony
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Old 01-25-2015, 03:31 PM
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Just find terminals R, L & 49a

None of these should contact the case in any indicator/hi/lo stalk position. Don't worry about the other stalks - they wont cause any issues here.

R & L should only ever contact to 49a and not both at the same time.

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Old 01-25-2015, 05:01 PM
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Thx Alan,

All are good and no pins on the combo switch drop to ground and the R & L all hit to 49a as required but not at the same time.

Also all of the wires that go from the Hazard Switch to the Combo Switch all have continuity as required.

So now my attention is on the Hazard Switch at the pod. Although there is no sign of burning or over heating in any way I am just checking its function. In open mode (No Hazard Lights) Terminal 15 is connected to Terminal 49 and I have continuity between them and all other connections in the switch are off. When the switch is closed (Hazard Lights On) I have no continuity between Terminal 15 and 49 but now I have continuity between 30 and 49. I also have continuity between Terminals 49a, R & L when the switch is closed. This seems right to me based on the schematic of the switch in the manual.

Your thoughts?

Thx

Anthony
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Old 01-25-2015, 05:53 PM
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That is correct - all sounds good.

I don't think the hazard switch was really ever a suspect here - the short must have been elsewhere on the L & R wires.

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Old 01-25-2015, 06:28 PM
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I agree completely Alan but thought I would check while I was there. I have attached a pic of the cut open harness and found the melted wire end. Hopefully the upload has not killed the pic much. I test continuity on this end of the wire to the hazard switch and I have continuity so at least I now have confirmation as to why I did not have blinkers.

You can see it at the top of the bundle sticking up greenish in color. The other end attached to the "B" Plug just pulled right out of the harness. Tomorrow I will check all surrounding wires as I have already found one with damage.

Thx for the help.
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Old 01-26-2015, 12:13 PM
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Originally Posted by Mrmerlin View Post
what most probably happened was that someone was removing the pod switches with the battery still connected,
and the switches were hanging out of the pod.
Then the turn signal switch was actuated or the key was turned on ,
and the headlamp or hazard or foglamp switch grounded out on the pod housing ,
(you will notice its made of aluminum.)
( you will also notice that there are metal parts that are exposed on the sides of the barrel switches)
This in turn fried the wire to the CE panel.

To fix it carefully remove the melted wire and examine any other wires that may have gotten damaged,
if your lucky you will only have to replace one wire from a switch to the CE panel,
so take your time,
keep the battery disconnected while working on the electrical system.

Dont ask me how I know this... Hard won experience
This is exactly what happened to me while working on the Stepson. Lesson learned (the hard way) It is not fun to replace the wires on the back of the CE panel. My hazard switch had come loose from the pod while I was moving the pod around and grounded one of the power tabs on the side of the switch to the aluminum pod housing. I turned the key and damn, there is a lot of smoke inside those wires.
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Old 01-26-2015, 03:43 PM
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Well today I am putting everything back together. I am replacing the wire that fried from the hazard switch to the "B" Plug on the CE Panel. So I cut back the tape holding the wires together at the switch about 3 inches and low and behold the wire is melted there as well but what was exposed to my eyes not taped was in perfect shape. Crazy stuff.

I am going to tell you what I think happened in the end although it is far fetched.

When I started to 1sft remove the CE Panel I had noticed a mouse urine smell and some mice feces in the corner under the CE Panel right at the "B" Plug. I think a mouse got there. urinated on top of the plug and while still wet someone turned the car on. That is what I think happened because there are absolutely no signs of s grounded switch, plug, etc. anywhere... just the remains of the mouse.
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Old 01-26-2015, 10:04 PM
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water/urine doesn't conduct well enough for that... so it can't have been that. Something like what Stan suggested makes the most sense.

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Old 01-27-2015, 10:02 PM
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Everyone thx so much. Powered car up today and blinkers worked perfect with no issues. all lights working now and with pod clean up I have adjustable dimmers on the pod and all lamps working inside the pod as well.

Now I just need to get the lights on all the switches to work. They work on the Hazards, fog lamps and OD but not the main light switch d-frost so I need to work on those next.

Also neither the front or rear wipers works so again next

A
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