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I am troubleshooting my AC, and it appears that the brown ignition wire is not plugged in on the ignition side of things. It has the 20 amp fuse and looks correct. According to the wiring diagram, it shows it just goes off to the ignition switch but it’s not specific on where to plug it in. Does anyone know where this gets plugged into.

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Well, it should go to your A/C blower control/fan speed switch if I remember correctly
 

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Well, it should go to your A/C blower control/fan speed switch if I remember correctly
That is correct, but I need to know where the other end goes. I am thinking it does not go to the fuse box since it has its own fuse. But I just dont see any where that makes sense to hook it into the ignition.
 

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Well, on later models, the brown wire went to the fuse box and the brown for the A/C went to the fuse box as well but upstream of the fuses. Same net effect.
 

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Well, on later models, the brown wire went to the fuse box and the brown for the A/C went to the fuse box as well but upstream of the fuses. Same net effect.
That is also correct. The brown ignition wire goes to the fuse box, but there is no place to plug in the AC wire. Also, coming out of the fuse box, every wire is accounted for and correct according the wiring diagram. So this is just a mystery to me :)
 

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That is also correct. The brown ignition wire goes to the fuse box, but there is no place to plug in the AC wire. Also, coming out of the fuse box, every wire is accounted for and correct according the wiring diagram. So this is just a mystery to me :)
Is there room on the ignition switch to connect it there?
 

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Nope. Everything looks correct there as well, no open spots that I can see.
Well, when you consider that the A/C was kind of an afterthought, feeding it from the ignition switch in the run position makes sense.
Here is a picture of how it was done on later models. You might have to add something to give you a place to land the wire.The brown goes to the fuse block and the A/C feed goes through a connector and then to the fuse box.

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I would be hesitant to run an extra significant load through the ignition switch. You are likely to shorten the life of the switch and introduce volt drops to other things that are fed from the switch. A better plan is to add an AC relay if there is not one there already.
 
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I would be hesitant to run an extra significant load through the ignition switch. You are likely to shorten the life of the switch and introduce volt drops to other things that are fed from the switch. A better plan is to add an AC relay if there is not one there already.
All I can say this that is how Alfa did it if you want to be original. That being said, I like that idea of an interposing relay to taker the load off of the ignition switch myself.
You could feed at A/C power through the cables coming from the battery at terminals 1-5 at the fuse blocks and then wiring the coil of that relay from the ignition switch. Sounds like a better plan that what Alfa had.
Looking at the wiring diagram, I see a couple of unused relay positions on the fuse block that could be used,
 
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I am troubleshooting my AC, and it appears that the brown ignition wire is not plugged in on the ignition side of things. It has the 20 amp fuse and looks correct. According to the wiring diagram, it shows it just goes off to the ignition switch but it’s not specific on where to plug it in. Does anyone know where this gets plugged into.
What year is your car? Hard to help if you don't provide that info. I do not see a brown wire on the A/C of either the S3 or the S4: the only brown wire I see carries power from the ignition switch to the fuse box.

Papajam's wiring diagram for the S4 A/C shown above doesn't match my car or the factory wiring diagram. On my '91 the A/C blower pulls switched power straight from the fusebox, and it does cause a significant voltage drop across the ignition switch. I fixed this by adding a relay to the system, but then of course my compressor took a dump.
 

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What year is your car? Hard to help if you don't provide that info. I do not see a brown wire on the A/C of either the S3 or the S4: the only brown wire I see carries power from the ignition switch to the fuse box.

Papajam's wiring diagram for the S4 A/C shown above doesn't match my car or the factory wiring diagram. On my '91 the A/C blower pulls switched power straight from the fusebox, and it does cause a significant voltage drop across the ignition switch. I fixed this by adding a relay to the system, but then of course my compressor took a dump.
It is an 83. That diagram is for a 1990 S# with Motronic. Just an example.
This is what he has.
 

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Discussion Starter #14
Well, when you consider that the A/C was kind of an afterthought, feeding it from the ignition switch in the run position makes sense.
Here is a picture of how it was done on later models. You might have to add something to give you a place to land the wire.The brown goes to the fuse block and the A/C feed goes through a connector and then to the fuse box.
I think I found a spot and hopefully makes sense. I plugged it into the fuse box on fuse 7 which comes off the brown wire. It shows 4 pink wires coming out of that which is what I have, but it does have an empty slot. If someone has a better spot I will be all ears. Thanks for your help!
 

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What year is your car? Hard to help if you don't provide that info. I do not see a brown wire on the A/C of either the S3 or the S4: the only brown wire I see carries power from the ignition switch to the fuse box.

Papajam's wiring diagram for the S4 A/C shown above doesn't match my car or the factory wiring diagram. On my '91 the A/C blower pulls switched power straight from the fusebox, and it does cause a significant voltage drop across the ignition switch. I fixed this by adding a relay to the system, but then of course my compressor took a dump.
Here is the portion of the AC system I am looking at, its from papajams wiring diagram.

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All I can say this that is how Alfa did it
And many people have had failed ignition switches, particularly from the starter solenoid circuit. Inductive loads cause arcing at the contacts when the switch opens and it is easier and less expensive to replace a plug-in relay. There were most likely only small volt drops in the switched circuits when everything was new but 40 years is plenty of time for contacts to develop surface resistance.
 

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Well, according to the diagram you posted, it feeds the fan switch, right? Is there an empty terminal on the fan switch?
 

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ok-- I got it. And you said there are no empty terminals on your ignition switch? Then I would say that wire should go into a connector off the ignition, look at the plastic connectors under there and see it it got pulled loose or was removed by a PO. I think you have identified the correct wire, with the 20 amp fuse inline.
 

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The wire is usually on the terminal on the power side of the fuse box. Not the fused side.

Reason being it has its own inline fuse.

Even though almost all of the 82 and later a/c's were factory installed. It was still based of the kit from the 70's. So Alfa just kept the inline fuse all the way to the end. In 87 they started using the ATO style inline fuse holder.
 
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