Need help tracing a wire - 69T

[keitho64]

Hello

I need some help tracing a wire. The car in question is a 69T, which is constantly blowing the number one fuse. What I have found is my ignition switch has two red wires connected to pin 15. These wires are energized when the switch is in the on position. With the wires connected the fuse will blow. With them removed the fuse is fine. I am enclosing a picture of where the wire connects on the firewall connection. It is the one with the ohmmeter probe connected. I have .3 ohms between the wire and ground so I am assuming this is the culprit. Does anyone know where this leads? My schematic does not show these connections and I thought I would ask the group before ripping into the harness to trace it. This is the 6-wire plug that the ignition switch plugs into.

I don't know how clear this picture will be, but if the 'key' is the 12 o'clock position, the wire I am tring to trace is at the 1 o'clock position.








I had this same problem a few months ago and I thought I had it fixed. While I was driving along at 60 the car just died and this is where I am left. I am sure there is a wire in this circuit that is shorted and the cause of my problem.

I will note that the starter, alternator, fuel pump, ignition module, distributor etc. are all disconnected so it appears to be a pinched or cracked wire somewhere. If anyone has an idea as to where this wire goes you could save me a ton of time tracing.

Thanks for any help you can shed.

[andyjboy]

Keith - large scale COLOURED wiring diagrams for early cars are here on Pelican :

http://www.pelicanparts.com/911/911_Parts/911_electrical_diagrams.htm


Andy Boyle(UK)
'69 911E

[keitho64]

Andy,

Thanks, I have that blown up and have been using it. However it is not very clear as to where the wire goes. I think I have no choice but to open up the harness and trace this wire to the end. Not exactly what I want to do.

Thanks

[keitho64]

One more comment, on the wiring diagram they list a Resistor (item 8) does anyone know where this is in the car? I cannot seem to find it and I want to check it out.

Thanks

[Jim Sims]

In later cars, I believe fuse one feeds the inside dome liights, clock and the front trunk light. In early cars It appears to feed the back-up and brake light circuits. The dome lights and front trunk light circuits are prone to short at the switches and light fixtures. The wiring to reverse the light switch on the tranmission can be damaged if the engine is removed while leaving the transmission in place. Check brake light switch at pedal assembly. It's not clear that fuse one is related the short you believe you have found at the ignition switch. Cheers, Jim

[keitho64]

Jim

Thanks for the feedback. What has me confused is it does not blow until the key is on. The head/tail/brake/backup lights all work without the key. I am not 100% sure my fuse block is original. I will double check the interior and exterior lights to be sure I am not missing anything.

I sure dislike troubleshooting electrical problems.

[dhoward]

The only resistor I'm familiar with is the ballast resistor in the ignition circuit. I'll try to trace mine at home tonight.

[keitho64]

OK I spent some time tracing wires again. First my 69 has 16 fuses in the trunk and two in the engine compartment. Who knows what a PO may have done.

What I have is one heavy gauge (maybe 12) wire on pin 15 of the ignition and one smaller gauge (maybe 16) wire on pin 15. I seperated the two and with the large wire connected and the key on the fuel pump and ignition are energized. When I connect the second thin wire the fuse blows. What I can tell is this wire goes to the resistor relay (item 51) in the wiring diagram. If I unplug the relay the fuse still blows. I need to trace this wire back and find the problem. I think I am almost there. Thansk for the advice and listening to my woes.

Happy New Year!

[dhoward]

Does yours look like this?
(sorry, sounded weird...)

[keitho64]

I have the two relays but no ballast resistor like that. I will try to post a picture later today when I go back to work on it. Your wiring looks the same as mine, thanks for the picture. I am thinking my problem is somewhere in the wiring by the socket for the relays. If I unplug the relay the fuse still blows but who knows.

How many fuses are in the front of your car? Mine has one 12 fuse connector and another 4 fuse connector. I traced them all last night. From what I can tell the fuses are as follows:

1 - unsure yet but it is related to the wire on pin 15 of the ignition - this is the one that is blowing all the time.
2 - Wiper/Washer
3 - Cigarette lighter, interior, clock, interior light
4 - Flashers
5 - Backup light, brake lights
6 - unsure
7 - Left turn signal
8 - Right turn signal
9 - Left high beam
10 - Right high beam
11 - Left low beam
12 - Right low beam

the four position block is:

1 - Tail Lights
2 - Front parking lights
3 - License plate, trunk lights
4 - not used

I counted 1 as closest to the passenger compartment.

Signed - Keith "still Shorted in Chicago" but at least the search has narrowed

[dhoward]

Keith, see if this helps. Not a great picture. The top 2 positions only have wires on one side of the fuse. Weird. as you can see, I need to do a little work in this area, but it seems as though everything works ok.

[keitho64]

Just for reference here is the wiring in the engine compartment and then the fuse block. As you can see this has been redone by a PO. I am trying to correct everything as best as I can while I am trying to find the short. My fuse box looks almost the same. As with yours, it works, I just like to know where everything goes.

The two position fuse block in the engine compartment only has one connection. It looks like the second is to feed the fuel pump after the relay. Right now the fuel pump is not on a relay. This is one of the things I plan to correct. I am going to take this whole panel out and check all of the wiring to the relay sockets. I am hopeful I will find the short here. If not, it must be in the harness somewhere. On the bright side, when this is done I will have documented all of the wiring and fuses plus put everything back the way the factory intended it to be.





I really appreciate you taking the photos. It sure helps for the reference.

[dhoward]

No. You don't have a yellow coil too?
I've got some kind of weird fuel pump arrangement wire-nutted.

[keitho64]

Yes I have a yellow coil as well. Works like a charm. Tonight I am going to take the rear panel out and check all of the wiring out. I will post some pictures of my findings later.

[keitho64]

OK here is how mine is wired now. Relay 6 is going to the fuel pump and relay 5 is for the defroster (which is not hooked up). Does this seem right?

[keitho64]

OK one more update. I think I have everything back to stock. I found out the ignition switch was wired incorrectly. I guess that explains the power drain when off. This is how I have the ignition switch wired now:

15 - +12v in the on position only one wire feeds the dash and one feeds to the engine compartment. Both are red wires. The one feeding the dash was causing the fuse to blow but not it is not.

54 - +12v in the On and Acc position. One yellow/red wire and one red/gray wire are connected here. These feed the radio and other accessories

50 - this is the yellow wire to the starter that provides +12v in to start position

PO - this has a grat wire connected and has 12V in the off position only. I assume this feeds the clock but am not 100% sure

30 - This is the +12v from the battery.

So here is my question, if the ignition switch was wired wrong could that have overloaded and been the cause of the short? Or, is it possible I have a gauge that is shorting out when it is hot? Finally, I guess it is possible that there is a wire that is lose somewhere in the dash that shorted out while I was driving.

It is running again, I have identified all of the fuses, relays etc. and documented everything.

Thanks fir all of the help and hopefully someone can use this information in the future.