Hello all, I have successfully swapped a 240D engine and manual trans in a Suzuki Samurai. I'm at the point where I need to figure out the wiring. I'm trying to wire the 240D alternator (55amp?)to the existing samurai wires. Samurai has a 45amp alt. However the wires are considerably smaller gauge compared to the Mercedes 3 prong wires. I am hesitant to splice 10g MB wire to a 16 or 18 gauge samurai wire. I don't want to burn anything. I'm also aware that MB over engineered everything and maybe the 10g is just over kill. I understand that the smaller gauge MB wire from the alt goes to the dash cluster "battery" light. The other two red 10 gauge MB wires go to the B+ on the starter. I have attached a schematic of the samurai alt wiring. Electricity is not my strong suit. I'm hoping someone can steer me in the right direction. Thanks didn't he help

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1981 240D auto
1977 240D manual 300 Turbo swap
1983 300SD
1983 300TD Parts car

Another diagram for samurai alternator.

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1981 240D auto
1977 240D manual 300 Turbo swap
1983 300SD
1983 300TD Parts car

I'm not sure if this is the complete answer. But, I referenced 310.15(b)16 of the National Electric Code. The table lists the allowable ampacities per gauge of wire based on the conductor temperature.

http://texaselectricalexcel.com/documents/DownloadTable310-15b16.pdf

10 gauge wire is acceptable for 30 amps at 140 deg F, 35 amps at 167 deg F, and 40 amps at 194 deg F.

16 gauge wire is acceptable for 18 amps and 18 gauge wire is acceptable for 14 amps.

Based on the amperage discrepancy, I would think if you adapt a 10 gauge to an 16 or 18 gauge with a 45-55 amp alternator, something is probably going to get fried. The table is for residential house wiring, so I wouldn't take it as gospel for 12V on a car, but I think it will probably be close for what the cables can bear without frying something.

Dkr.

That is what I thought was weird is a 45 amp alt from the samurai would have such dinky wires.

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1981 240D auto
1977 240D manual 300 Turbo swap
1983 300SD
1983 300TD Parts car

There's probably some details missing. I haven't looked into alternators before. There would be a difference in what cables you can use if it is always putting out 45 amps vs. just peaking at 45 amps. It is also possible that it may be rated for 45 amps but put out a lower real-life rating. Those are the kinds of things that car makers would be looking at. I have no idea how it plays out in real life.

I hope the swap works out for you. I have a TDI engine I am planning to put into a Samurai or Tracker once I find a decent donor vehicle.

Dkr.

I was going to do the VW diesel route which would have been way easier given the commercial conversion kits that are out there. I had a running 240D engine and I couldn't say no.

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1981 240D auto
1977 240D manual 300 Turbo swap
1983 300SD
1983 300TD Parts car

I think it would still be a great swap. At least you don't have to deal with the electric IP and and regular timing belt changes. The diesel really brings a lot of new possibilities to the Samurai platform.

Dkr.

If you are unsure run the wiring directly from alternator B+ to the starter B+.

Note that the B+ wire on the Suzuki is the big screw terminal one, not the three spade posts. IGnition, Lamp, Sense are low current wires so they don't need to be thick gauge, only the B+ carries the alternator rated current.

D+ goes to ignition warning light, originally marked L in the suzuki wiring. Leave S(or D, sense or dummy) and IG (ignition) unconnected, as the Bosch alternator does not need them.

The only wire that carries heavy current is the B+ wire. The others are all low-current connections. If you're asking how to connect a Mercedes alternator with the three-way connector, the two large tabs on the Mercedes alternator are B+. You can attach the existing B+ wire to either of these. Run another 14 gauge wire from the second B+ tab to the main B+ junction.

For the bulb circuit, just run the L wire to the small tab on the alternator (which is D+). The Bosch alternator has no Ignition or Sense tab, so these wires should be taped off, just be careful to tape up the IG wire AFTER the bulb connection.

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Don't forget to let us know how it drives and post up some photographs .

I agree : simply run a new 10 gauge wire from the B+ alternator terminal to the battery or hot terminal on the starter .

I prefer to run direct battery current to the alternator as each connector loses one 10th of a volt or so when new .

If you make up a new sub harness, add a brown ground wire between the alternator and battery too .

Of course only BOSCH or HELLA branded voltage regulators ! .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

On the Mercedes Alternator the 2 wider terminals actually end up at the battery.

The shorter width terminal goes to the Ignition and needs to have at least a 3 watt light bulb in the circuit it is not supposed to charge.

That means circuit "L" on the Sumari needs to go to the shorter width terminal on the Mercedes Alternator.

And both of the wide terminals would go to the "B" circuit on the Sumari. As mentioned that is the terminal that needs to take the amperage.

See attached pics and read text. In the Alternator Schematic you see that the 2 wide connector terminals actually end up at the Batter +terminal and are in the end connected direct to that terminal.

So that takes care of the charging of the Mercedes alternator. However the

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84 300D, 82 Volvo 244Gl Diesel