74 S2 Spider Battery to Starter Wiring Wrong? - Alfa Romeo Bulletin Board & Forums
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post #1 of 18 (permalink) Old 09-19-2019, 07:37 PM Thread Starter
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74 S2 Spider Battery to Starter Wiring Wrong?

Hello Ė this is my first post. Thank you to those that have shared so much insight here.

I hadnít had an Alfa for quite a few years, but a couple of years ago picked up a nice Ďdriverí 1974 S2 Spider. I proceeded to enjoy driving it and tinkering, quickly learning that changing out the fan blower requires just Ďa bití of disassembly.
When I last worked on it long ago, as I took things apart to attempt the blower replacement, I came to discover that a PO had long ago modified quite a bit of under-dash (everywhere actually) wiring to install a 1980ís vintage alarm.

Life has a habit of getting in the way, and only recently have I dusted off the Alfa to continue, the passage of time has complicated my task it seems. When I took things apart back then I took pictures to ease the reassembly. However since then Iíve changed phones, etc. and no longer have the pictures ☹. I thought no problem, I have one one of Papajamís wiring diagrams he provided me back when I first started. Thatís where I am now, only to find that some significant bits of my cars wiring donít look like that diagram. Sorry for the long intro, attached are pictures and my initial question follows. Thanks in advance for any insight you can provide. In terms of mechanicís skills Iím not a novice, but Iím not particularly good either LOL.
The diagram indicates thick red wire running from battery positive to starter solenoid, but instead my car has thick black wire running from battery negative under engine to starter solenoid Ė thatís pretty different so I figured I should either confirm or correct before going any farther. Note that the thick red wire shown attached to solenoid appears to come from the fuse panel via cowl.

Thoughts?
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post #2 of 18 (permalink) Old 09-20-2019, 12:15 AM
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It looks like there is some confusion over the wiring colours there. The red wire on your battery should be earth, this is easy to confirm, trace the red wire from the battery, I believe you will find it goes to earth, now remove it from the battery and run a OHM meter between the terminal and the engine block, any resistance? Thought not, thats the earth lead. The Battery is in the wrong way around +earth. Again, double check (measure twice, cut once), reconnect the battery the other way around, black wire to +, red to earth, that sounds so wrong! Now use your meter to check you have 12v + at the starter, you should have.
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Daily drive is a Giulia 2.0 MA, wife drives a 939 Spider in the summer and a Abarth 595 in the winter. For special sunny days we have a S2 Spider Junior in the garage.
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post #3 of 18 (permalink) Old 09-20-2019, 12:51 AM
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It looks like there is some confusion over the wiring colours there. The red wire on your battery should be earth, this is easy to confirm, trace the red wire from the battery, I believe you will find it goes to earth, now remove it from the battery and run a OHM meter between the terminal and the engine block, any resistance? Thought not, thats the earth lead. The Battery is in the wrong way around +earth. Again, double check (measure twice, cut once), reconnect the battery the other way around, black wire to +, red to earth, that sounds so wrong! Now use your meter to check you have 12v + at the starter, you should have.
Right. My S2 spider (actually all Alfa Romeos and most cars I know off) have negative earth which is usually connected with black wires. Red (hot) is usually marked with red wires.
My guess is that the battery is placed wrongly (flipped frontside / back if I can read the +/- right under them cables) and I really doubt that the car ever started or ran in this set-up (not without the battery exploding I would think).

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post #4 of 18 (permalink) Old 09-20-2019, 03:11 AM
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? now I'm confused

I can see a + sign under the red wire and a - sign under the black. To me that is correct.
(If it were the other way around, there'd be some serious melted wires around!)

If you flipped the battery around, wouldn't the posts be right near that hold down bracket and just looking to short out?

positive post of a battery is always slightly larger than the negative post to avoid clamping the terminals on wrong (at least with top post batteries)

Dom - Alfa Spider 1990 S4 - formerly: Alfa 101 Sprint, 2600 Sprint, Montreal - family classics: Jensen Interceptor II, '58 Hooper RR Silver Cloud I, Shadow II, '60 Corvette.
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post #5 of 18 (permalink) Old 09-20-2019, 08:27 AM
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? now I'm confused

I can see a + sign under the red wire and a - sign under the black. To me that is correct.
(If it were the other way around, there'd be some serious melted wires around!)

If you flipped the battery around, wouldn't the posts be right near that hold down bracket and just looking to short out?

positive post of a battery is always slightly larger than the negative post to avoid clamping the terminals on wrong (at least with top post batteries)
Sorry, I can't tell for sure from the pictures but, yes, positive plug + on the battery "usually" connects to red cables and feeds into the wiring loom and ancillaries (as in starter). Negative plug - usually connects to short black cable which runs a foot or less before being earthed / fixed on the body.
Wish I could post photos but my spider is completely stripped to the bare metal at this time. Name:  DSC_3060.jpg
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post #6 of 18 (permalink) Old 09-20-2019, 08:50 AM
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Wish I could post photos but my spider is completely stripped to the bare metal at this time. Attachment 1589586
looks like an E type coupe on the side, keeping the spider good company
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Dom - Alfa Spider 1990 S4 - formerly: Alfa 101 Sprint, 2600 Sprint, Montreal - family classics: Jensen Interceptor II, '58 Hooper RR Silver Cloud I, Shadow II, '60 Corvette.
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post #7 of 18 (permalink) Old 09-20-2019, 09:02 AM
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IF what i remember from basic electricity classes is correct: since all the components in a car are direct current, reversing the leads will make everything run the opposite direction. not such a big deal for windshield wipers but now your defroster is a "froster" and you have five reverse gears and only one low forward gear.
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post #8 of 18 (permalink) Old 09-20-2019, 09:21 AM
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IF what i remember from basic electricity classes is correct: since all the components in a car are direct current, reversing the leads will make everything run the opposite direction. not such a big deal for windshield wipers but now your defroster is a "froster" and you have five reverse gears and only one low forward gear.
... Don't listen to him the "froster" may work in reverse but the gearbox is not electric at all

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post #9 of 18 (permalink) Old 09-20-2019, 09:27 AM
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looks like an E type coupe on the side, keeping the spider good company
Yuppppp, but not mine. 1966 Series 1.5 with the toggle switches, so more valuable than the spider would ever hope to be but for some reason it keeps getting smaller and smaller in my eyes... Used to love the e-type but this girl has done it for me.

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post #10 of 18 (permalink) Old 09-20-2019, 10:14 AM
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Looking again, you can see the charge lead from the alternator goes to the red lead, so that confirms it is wired the correct way. The battery in my S2 is the other way around, both + and - are both black. I'd start as I said earlier check everything with a meter, follow the route of that red wire, no guess work.

Daily drive is a Giulia 2.0 MA, wife drives a 939 Spider in the summer and a Abarth 595 in the winter. For special sunny days we have a S2 Spider Junior in the garage.

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post #11 of 18 (permalink) Old 09-20-2019, 03:42 PM Thread Starter
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Thank you all, for the advice as well as a giggle or two. Everything I see and read here from y'all indicates the 'corrected' way for my car will be to flip the battery and connect red cable to -/earth and black to +, checking with meter as I go. As I looked more closely the red wire (that appears to be too long) is currently terminated to ground.
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post #12 of 18 (permalink) Old 09-21-2019, 12:33 AM
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Where does that red lead that goes from the back of the alternator go? THAT SHOULD NOT GO TO EARTH!!! It looks like you have a battery with the wrong post configuration, which is adding to the confusion.
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Daily drive is a Giulia 2.0 MA, wife drives a 939 Spider in the summer and a Abarth 595 in the winter. For special sunny days we have a S2 Spider Junior in the garage.
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post #13 of 18 (permalink) Old 09-21-2019, 12:54 AM
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Where does that red lead that goes from the back of the alternator go? THAT SHOULD NOT GO TO EARTH!!! It looks like you have a battery with the wrong post configuration, which is adding to the confusion.
This is how I have (had...) it. Let's forget colors for a little bit and look at the symbols embosed on the battery itself :
1. The battery's "-" plug needs to be connected to the short (15 cm or so) cable which is screwed & fixed directly on the body (earthed)...
2. The battery's "+" plug needs to be connected to long and thick (possibly multiple, 2 or 3) cable bunch which feeds into the wiring loom and various ancillaries.
In my 3 Alfa Romeos, my battery is positioned exactly like the picture above, negative - towards the front bumpers and grill (earthed/anchored to the body) and positive + towards the rear (feeding into the wiring loom).
Again I say ignore the color and trace tge direction where the cables are going to make sure all is well.

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post #14 of 18 (permalink) Old 09-21-2019, 02:15 AM
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Everything I see and read here from y'all indicates the 'corrected' way for my car will be to flip the battery and connect red cable to -/earth and black to +, checking with meter as I go. As I looked more closely the red wire (that appears to be too long) is currently terminated to ground.
?? well you see that can't be correct! I think you have it correct as is! (like I said above)
Let's look at your photos:
The +Plus post of battery (ignore for now which way the battery is turned!) it has 2 reds bolted to it: a very thick red and thinner red....correct?
In one photo I can see the thinner red going to the alternator (hopefully B+ post) ...correct? (oh and remove and clean those rusty connections or you will, I guarentee you, get future problems!)
and I can see that thick red going to starter..correct?

If so....that, to me, is all correct---- just be certain the thicker red is going to the starter

Now follow that black wire on the battery -Negative (Ground) post.....that should be bolted to the chassis somewhere....is it?


nb: (not that you will be doing this) but anyone leaving a thick red wire as a ground is just doing a bodge job: some future mechanic or roadside AAA man is goin' to make a mistake, either trying to roadside boost the battery, testing electrics, whatever...and will blow your alternator or something
(and you'll of course get the honorary title of 'DPO' with the next owner)
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Dom - Alfa Spider 1990 S4 - formerly: Alfa 101 Sprint, 2600 Sprint, Montreal - family classics: Jensen Interceptor II, '58 Hooper RR Silver Cloud I, Shadow II, '60 Corvette.

Last edited by spiderserie4; 09-21-2019 at 02:21 AM.
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post #15 of 18 (permalink) Old 09-21-2019, 03:50 AM
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Dom, the OP has already said that the red cable (attached to + ) goes to ground. There is nothing, as already said, can be judged from the colours of (these) wires, indeed if that red wire does go to earth it should be replaced with a black one. The only way to ensure wiring is correct is by the OP tracing the wiring, and using a meter to confirm continuity and lets be clear, forget colours, the wire from the alternator B post must go to the same terminal that is connected to the starter, the + terminal. This battery in the OP car is the wrong way around! 55amps at 12V can cause some serious burns and at worst a fire if its all wrong.
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Daily drive is a Giulia 2.0 MA, wife drives a 939 Spider in the summer and a Abarth 595 in the winter. For special sunny days we have a S2 Spider Junior in the garage.
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