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Discussion Starter #1
Wanted to get some feedback from y'all. Have a brand new battery in my spider but if the car sits overnight it won't turn enough voltage to fire up the systems. Jump starting starts the car immediately but obviously this is not an ideal situation. With the car running I'm reading between 12.9 and 13.0 volts at the terminals. Voltage reading is the same with the car running about 2000 rpm. Y'all think that the battery charge is being compromised by only getting 13V from the alternator and subsequently causing this issue? My next task is to thoroughly clean the terminals, the ground, and make sure alternator connections are secure. I would like to see at least another .6 volts or so at the terminals. Last question- My understanding is that there is a junction box inside the fender where I might be able to check alternator output from before it gets to the battery... Is that correct?
 

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The battery will likely not get re-charged if it is getting less than 13.8 - 14.2V.

There is a junction box on the left inner fender - it'll have 3-4 red wires and a pair of smaller green wires. The alternator output goes to the junction box and thence to a connection at the starter motor and an to the battery. With the battery disconnected (those red wires will be 'hot' otherwise), remove and clean all those connections. And the ground connections, too. There is (should be...) a ground strap between the bell housing and a tab in the transmission tunnel (you have to get under the car to find it). And the battery ground cable attaches to the body behind the battery - make sure these are all 100% clean & tight.

Make sure none of the interior lights are switched to 'always on'. The footwell light lens is also the switch. One position is automatic (on/off with the doors open/closed), one position is off and one position is always on. Since they are not very bright, they can get moved by an errant foot to always on. If you have a light inside the glove box make sure that isn't stuck on, too.
 

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Jump starting clamps can cause battery terminals to make better connections or worse connections with the cable/post connection.

Measure the voltage at the starter pos. connection. Then wiggle/grab/tap ( don't break anything! ) the battery connections, measure again.

How ya dooin? Suspect the Battery clamps.
 

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Discussion Starter #4
Thanks as always for the excellent feedback. After I posted, I went to the garage and cleaned the battery cable terminals and the posts on the battery thoroughly. Also unbolted the ground at the rear of the car and noticed it was full of corrosion and oxidation. Cleaned the heck out of that as well, and then tried to start the car. Car started right up, but I was getting 13.2v at idle. So obviously a small improvement. After that I thoroughly cleaned the little junction box in the engine compartment. It seemed dirty as well, so I'm hoping I get some results from that also. By the way, I did make sure the interior lights stayed off during this process. Really seems like my problem might be compromised connections so far... Ran out of time so I will see how she does on the drive I'm leading tomorrow. I will keep my handy jump starter with me just in case. 😁
 

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Discussion Starter #5
Measure the voltage at the starter pos. connection. Then wiggle/grab/tap ( don't break anything! ) the battery connections, measure again.
This is on my list, as well. This will be a very telling test to do. Although I suspect that a failing alternator would probably show more of a voltage drop than this, correct?
 

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Definitely clean all the connections, a friend with a similar spider just did the same with good results.

But you might also look into a new voltage regulator. On Bosch alternators they are replaceable. Mine was dying on my Berlina and I was only getting 13V when charging. I swapped in a different regulator and got it up closer to 14V.

Sent from my ONEPLUS A3000 using Tapatalk
 

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cleaning the battery ground bolted to trunk improved the voltage reading some, but 13,2 idling is still, imo, too low.

remove the voltage regulator (very easy) and inspect the brushes.
check if they are worn down a lot or worn unevenly (latter is a sign of commutator wear)
one of the screws holding it in is a ground against the alt. body, make sure that too is clean.

remove the alternator connections and clean them up, whilst you're there!

it is a cheap part to replace, and removes it from the equation.
 

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Discussion Starter #8
So... voltage at the battery today this morning before our drive was up to 13.4-13.5V at idle. This was the result after cleaning the little junction box in the engine compartment... Did not have any starting problems today during or after our club drive, which is a positive sign. Going to continue to check and clean the alternator connections, but at this point if I don't recover any more juice from the obvious I will inspect and possibly replace the voltage regulator.
 

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always consider bad connections on anything electrical alfa romeo.
first check its all the main earth straps and battery mains.
the alternator will change its output depending on the charge state of the battery. keep that in mind when testing.
test above 1500 rpm and at idle. no charge at idle can mean alternator issues. (brushes, regulator, rings)


check our youtube video
Bad Ground - How to Test by Moss Motors, Ltd.
also they have other good related videos
Alternator - How to test using a Voltmeter
 

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On my last 115, this problem was traced to a badly internally corroded/degraded wire between the alternator output (B+) post and the previously discussed junction post. Many others have had the same problem. The ONLY cure is a new wire.

I made one from heavier gauge wire, as it was likely extended heating that degraded this wire. I didn’t bother removing the old wire or reinserting the new wire into the factory bundle. It’s a short run, and zip ties cleaned it up.

The problem is that the degraded wire can no longer carry the amperage being demanded by the car’s load, so the voltage drops.

Easy job. I’d enjoy hearing about the result.
 

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Ramping up the output voltage in an effort to overcome a damaged wire will not produce a happy outcome. Find the problem before making mods.
 
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