Alternator Field Wire; 1986 Spider

[Moon96815]

1986 AR Graduate Spider 1966cc w/5 speed manual trans w/Bosch L-Jetronic Fuel Injections system. This makes it an "S3" American, I think. It has 175,000 miles recorded thereabouts.

I am mentoring the young (21 yo) owner of this vehicle which has multiple issues. The alternator was not putting out and draining the battery. 11.5 V at the battery and at the fender well relay post to which the alternator output (red) and field wire (green) are attached for relay to the system.

We removed the alternator and had it bench tested at a local shop; it put out 14V @ 60A (rated at 14V @ 55A) and held a steady 14V with no load so the alternator itself is OK.

Belatedly, we checked the green field wire voltage supply and found that it had no voltage. We then traced the field wire back to the instrument panel and identified the other end with a multimeter. The field wire is continuous (and reads 10 ohms to engine ground). We found battery voltage at the pink wire on the same connector as the field wire at the instrument panel (top middle white connector, I think, with about 10 wires in the harness. The green wire path on the circuit board is also directly connected to the voltage indicator instrument light on the board so this seems correct.

The problem is that when the ignition key is turned to the "ON" (run) position the green wire is NOT energized which it seems that it should be to energize the alternator and to activate the voltage indicator on the dash.

The 10 ohms to ground resistance of the green field wire seems correct; am I correct that it should be at ground or thereabouts?. We checked the fuse box and all fuses are continuous and the box is energized with battery voltage.

Now for the "devil in the details" part. Some previous owner had evidently had problems with his steering column mounted headlight switch and so he opened up a packet of wires and spliced a toggle switch into a battery voltage feed (red) and then connected the other end of the toggle switch to the column mounted headlight switch (yellow). This produced headlights at one time and is not working now for some random reason.

I should also mention that the top of the instrument cluster was heavily corroded with iron oxide indicating that it was exposed to rain water or something. We carefully cleaned nuts, bolts, circuit board copper etched paths around the circular "mosquito lamps" (wiping lightly with white vinegar) and the contacts on the lamps themselves. We checked continuity of the lamps etc. It was a 75 minute project with two people. The end result was satisfactory in my opinion. We also attempted to clean the wiring harness connectors by connecting and reconnecting the harness to the instrument cluster copper array connectors which where clean.

I am concluding a burnt ignition switch and possibly a burnt headlight switch. Any comments appreciated.

[ghnl]

I suggest contacting BB member Papajam. Send him a PM (Private Message) requesting copies of his color-coded wire diagrams for that model Alfa. Include your email address and he'll send some .pdf files that will make chasing Alfa electrons much easier.

[papajam]

Quote:

Originally Posted by Moon96815 The problem is that when the ignition key is turned to the "ON" (run) position the green wire is NOT energized which it seems that it should be to energize the alternator and to activate the voltage indicator on the dash.

[ghnl]

And, IIRC, that bulb has to be a specific wattage. (which does not mean I remember what wattage that is...)

[Moon96815]

Quote:

Originally Posted by papajam It could as simple as the indicator bulb being burned out.

[Moon96815]

Quote:

Originally Posted by ghnl I suggest contacting BB member Papajam. Send him a PM (Private Message) requesting copies of his color-coded wire diagrams for that model Alfa. Include your email address and he'll send some .pdf files that will make chasing Alfa electrons much easier.

[Moon96815]

I just opened my email and received the diagram from Papajam; much thanks indeed. Is it suggested that I donate to the forum or to him personally. I use PayPal. Thanks.

[DPeterson3]

Moon,

Before spending too much brain time on this, run a completely separate, new wire from the alternator B+ (main power out) terminal to the stud on the left front wheel well where the original red main-power wire connects. It is a common problem that the original wire can appear OK, but refuse to carry current. After much head scratching and testing, I followed the experience of others on the BB who had this problem, and it cured my alternator output issues. You can leave the original wire in the bundle and just run a new one, or fiddle the old one out and run the new one as part of the old bundle. The main thing is to NOT believe your eyes, and try a replacement main-battery output wire.

[Moon96815]

Quote:

Originally Posted by DPeterson3 Moon, Before spending too much brain time on this, run a completely separate, new wire from the alternator B+ (main power out) terminal to the stud on the left front wheel well where the original red main-power wire connects. It is a common problem that the original wire can appear OK, but refuse to carry current.

[DPeterson3]

I probably wasn't clear.

There is a reddish (I think) wire that goes from the largest terminal on your alternator up to an even larger stud that is mounted on the left wheel well. The large stud on the wheel well has several wires terminating there. Put a new wire between the largest stud on the alternator and the bigger stud on the left wheel well. Ignore all the voltage tests, labels, etc. Try this. It is super easy to do, as you just make up a fat piece of wire with two ring terminals and screw it in place. The original wire appears too small of a gauge to me, so I used something fatter. Don't recall the gauge, however. Use your eyeballs and pick something fatter than the original. It's easier to get to the alternator by removing the air filter tray, and probably quicker than trying to work around it.

[Moon96815]

Quote:

Originally Posted by DPeterson3 I probably wasn't clear. There is a reddish (I think) wire that goes from the largest terminal on your alternator up to an even larger stud that is mounted on the left wheel well. The large stud on the wheel well has several wires terminating there. Put a new wire between the largest stud on the alternator and the bigger stud on the left wheel well. Ignore all the voltage tests, labels, etc. Try this. It is super easy to do, as you just make up a fat piece of wire with two ring terminals and screw it in place. The original wire appears too small of a gauge to me, so I used something fatter. Don't recall the gauge, however. Use your eyeballs and pick something fatter than the original. It's easier to get to the alternator by removing the air filter tray, and probably quicker than trying to work around it.

[DPeterson3]

I was not referring to the relay post, just to a gang-post on the wheel well. I was not referring to the field wire, but to the main bus feed wire from the alternator to the gang post.

The main bus wire from the alternator to the post is wrapped up in a bundle of wires, so it is interesting that you removed it to test it. The normal procedure would be to disconnect this wire at the alternator in order to remove the alternator. I didn't bother removing the original wire from the wrapped bundle, and just tie-wrapped the new wire along the bundle when I determined that it was the problem.

If it is not the main feed wire, that's OK with me, but all I can repeat is that I am NOT referring to the field control wire or the relay post. It is just a gang post on the wheel well.

Of course, you can chase the problem, and it could well be something in the excitation circuit. I was just trying to share that the main bus wire is a common failure point, and very easy to replace without a lot of bother to test.

[Moon96815]

Quote:

Originally Posted by DPeterson3 I was not referring to the relay post, just to a gang-post on the wheel well. I was not referring to the field wire, but to the main bus feed wire from the alternator to the gang post.

[alfabeach]

I also changed the power wire from the alternator to junction box like Don. Also I added a ground wire from the alternator bracket to engine mount. This helped a low voltage problem for me. All the relays you see are for my headlights and fog lights. This does not address your question directly, but helped me and others.

[papajam]

Quote:

Originally Posted by Moon96815 The problem is that when the ignition key is turned to the "ON" (run) position the green wire is NOT energized which it seems that it should be to energize the alternator and to activate the voltage indicator on the dash.