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Discussion Starter #1
Nappy New Year all Alfisti.

Today I have resolved to selfishly do only things Alfa related so let's start this fine year with my low hanging fruit.

Jenny (1993 164L) has a dead short in the courtesy lights and front cigarette lighter circuit.
The lowest leftmost 15A fuse blows immediately whether the door is open or closed.
I disconnected all the courtesy lights and front cigarette lighter at their respective connectors.
All these units looked good anyway.

I am now faced with opening up each door to check internal wiring and the courtesy light switches.

Is there a known issue in this area?

Is there a better way to track down the short?

Any input will be greatly appreciated.

Ta,

Neville.
 

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How about the red light wiring in the end of the arm rest? Have you had arm rest off or the rear mounting screw out. I have that wiring pinched by rear screw after changing a window regulator and inner door handles.
 

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Can you check for a short circuit at each connector you disconnected when you disconnected each affected light and the power outlet (surely not a cigarette lighter these days?) with your multi meter until you locate the wiring segment that has the short in it. With the doors closed the courtesy lights should each be open circuit at their respective connectors. Plus all those connect to the delay off relay and to the control unit that powers them all off after a few minutes to prevent battery drain if the door or trunk switch remains active due to failure to completely close a door or the trunk lid.
 

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Discussion Starter #4
Thanks Steve,

I will start with the driver door as that's where most of the "action" occurs.
Getting into that door properly will entail removing all the panels and armrest etc.
I will report back later.
 

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Discussion Starter #5
Thanks Michael,

I will do as you suggest.
I have never used a multimeter to test for a short so I will go learn how to do that.
 

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You get zero resistance (ohms) across the terminals of the device you have removed. That indicates a "switch" is in the on position. If you know the switch is off (or circuit fuse is blown or removed) then you have a short somewhere you're not supposed to have, equivalent to an on switch, which measures on the multimeter as zero resistance or closed circuit. Since you know the circuit is supposedly open you should get maximum resistance.

When the multimeter is set to ohms touching the pins on the leads gets you zero resistance. With air between the pins you get maximum resistance.

The tricky part is narrowing down the circuit which has the short. If you're lucky it will be confined to the one circuit feeding the device you have just tested the connections for.
 

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Discussion Starter #7
Thanks Michael,

I appreciate the tutorial.
I always managed to diagnose electrical faults by gut feel and unplugging/plugging stuff.
Owning Alfa's I really should learn more efficient methods as you just posted so nicely.
As usual I have been sidetracked and not yet revisited this issue but the weekend ahead is to be dedicated to Alfa's.

Ta,

Neville.
 

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Well, that method works also if the device itself is causing the short. You can use several fuses sacrificially to eliminate each device as a potential cause. I think you have decided that all the devices are ok. If so then you face the more difficult troubleshooting for a stray dead short somewhere in the wiring of those circuits. Not an easy thing to do.
 

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I have done the same thing as Steve posted, it is very easy to pinch a red armrest-end light wire when reinstalling the armrest, even when you think you are being careful.
Charles
 

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My 164 had a short to ground on the passenger side rear courtesy light that prevented my electric radio antenna from working (perhaps they are on a common circuit?). When I removed the courtesy light to check the bulb, after replacing the fuse, I noticed a spark from where the insulation had been rubbed off the wire by the 'C' pillar.

More recently, I had a similar issue where the power antenna would blow the fuse every time it went up or down. Interestingly that issue went away after pulling the engine and transmission for a major service, clutch assembly replacement and power steering rack rebuild. Now if only the power adjusting mirrors would work...

Mark
 

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My 164 had a short to ground on the passenger side rear courtesy light that prevented my electric radio antenna from working (perhaps they are on a common circuit?). When I removed the courtesy light to check the bulb, after replacing the fuse, I noticed a spark from where the insulation had been rubbed off the wire by the 'C' pillar.

More recently, I had a similar issue where the power antenna would blow the fuse every time it went up or down. Interestingly that issue went away after pulling the engine and transmission for a major service, clutch assembly replacement and power steering rack rebuild. Now if only the power adjusting mirrors would work...

Mark
You are on the right path... Why do you think the mirrors don't work? They run on the same circuit as the antenna and the door lights. Clean your switch and check the wiring to the mirrors. On mine operating the mirror switch would immediately blow the fuse, cleaned the internal contacts and bam, no more short and I have functioning mirror controls.
 
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