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SWEM B18 Delco Alternator Conversion
Phil Singher

I have long felt that the original charging system on the B18 motor was marginal at best. Add some modern demands like halogen lights, electronic ignition and a two-way winter commute in the dark, and "marginal" turns into "inadequate." The original generator only puts out 25 amps or so, and this has to recharge the battery after starting while every electrical system in the car is simultaneously draining it. To make matters worse, the generator does nothing at all at engine speeds under 1500 RPM -- all that time you're sitting at a red light is pure electrical loss.

To compensate, I long since learned to use the biggest battery that would fit in our Amazon, and to scrimp on electrical loads when driving in town -- like using the heater blower only when stopped, and the wipers only when moving. While it's normal, I never liked the look of that dimly glowing red light on the dash when going down the highway with everything running, either.

These problems are inherent in the way generators work; it's not that there's anything wrong with or peculiar about the Bosch units. In a generator, all the output current flows through the brushes, and the rate of that flow is limited in the voltage regulator to prevent burning the brushes. The spinning armature in a generator is heavy and complex, so the size of the pulley is chosen to prevent its flying apart at high engine speeds. Consequently, at idle, the generator simply doesn't spin fast enough to produce a DC voltage high enough to charge the battery.

The alternator, an "AC generator," avoids these problems. The rotating part is lighter and simple, permitting use of a small pulley and good output at slow engine speeds, and the brushes supply current through the slip rings only to the internal loads of the unit. The output current requires no limiting, although voltage is still regulated to prevent cooking the battery. So why didn't auto manufacturers always use these, you might wonder? Because the AC produced has to be rectified (turned into DC) before the battery can use it, and high-current, solid-state rectifiers simply were not available commercially until the early 1960s (does the term "semiconductor" mean anything to you?).

Volvo introduced a Bosch alternator into its cars along with the B20 motor in 1968, and subsequently increased its output further to meet the demands imposed by electronic fuel injection in 1970. Unfortunately, these alternators will not bolt to a B18 block -- the mounting bosses are cast differently. What's required is a custom bracket, and, well, I'm no blacksmith.

Salvation came courtesy of Ron and Wendy Kwas, and was found on the Swedish Embassy web site. They produce a number of well-thought-out, hand-made "SWEM kits" to fit the 544, Amazon and 1800-series cars, and among these is an alternator conversion kit. Rather than simply make a bracket to adapt the B20 Bosch unit to the B18, the kit is designed to mount a modern, American-made Delco-Remy alternator producing up to 63 amps -- enough power to keep Tim Allen happy. This alternator is readily available new or rebuilt, requires no external voltage regulator, and is easily serviced with parts you can get anywhere in North America.

With the days growing shorter and the prospect of a season of El Niño-driven storms looming, I ordered the alternator kit and another SWEM electrical improvement: a reworked, high-zoot fuseblock (available exchange only, and not for 1800).

Unfortunately, the alternator brackets were out of stock, so I had to wait a bit until the next lot was produced "at the foundry" -- I guess neither Ron nor Wendy is a blacksmith, either. I promised to be patient, and they dispatched the fuseblock to me in short order.

Fuseblock replacement is a matter of ten minutes or so -- simply disconnect the battery, unmount the old block, swap the wires and fuses over, and mount the new block (now you can reconnect the battery). I went so far as to put in all new fuses (OK, I admit it, I'd had a piece of paper clip doing the 25 amp duties for a couple of years). The new block was shiny clean, the bolts through soldered for zero resistance connections, and the fuse clips and spade terminals were coated with dielectric grease -- this makes an air-tight seal on the connections and prevents future corrosion. Considering the simplicity of this installation, the directions provided with the fuseblock were very detailed and full of helpful hints.

This provided some relief all by itself -- headlights became a bit brighter, and the ominous red "idiot light" on the dash now gave a dimmer glow with all systems running. Still, the fuseblock has nothing to do with the actual charging of the battery. I waited eagerly for the alternator kit.

Which finally arrived, just in time for Christmas. Be aware that the kit does not include the actual alternator -- you have to come up with that yourself. What is included:

  • A nice, heavy-duty bracket, painted authentic "old Volvo motor red."
  • Bullet-proof hardware to mount the alternator to the bracket.
  • A connector that plugs into the alternator with leads to crimp onto your (modified) wiring harness.
  • Comprehensive, step-by-step instructions including "before" and "after" wiring diagrams, photos of the alternator, and service and troubleshooting instructions. Excellent!

The Delco-Remy SI-10 alternator is available in a variety of outputs and orientations -- you can get them with the connector sticking out the top or the side, and with a range of pulley sizes (2 to 2-1/2 inch OD is ideal). I went with the unit shown in the photos, which has the connector on top. As it worked out, this put the connector uncomfortably close to the ipd header on our car, although it would be fine with any of the stock exhaust manifolds. If you have the header, I recommend you choose a unit with the connector pointing towards the right fender when mounted.

The new bracket bolts up without the original shock mounts (did those actually ever do anything?), which means the bolts may bottom in the block before fully securing the bracket. You can easily compensate for this on the middle and rear bolts by adding a lock washer outboard -- on the forward bolt, such a washer interferes with mounting the alternator body, so I just substituted a shorter bolt in that location. The holes in the bracket are drilled slightly oversize to permit some forward / back adjustment of the bracket to align the pulleys.

The alternator mounts to the bracket with a single hex-head bolt (you'll need a 5/16" hex driver) which passes through the front of the bracket, the alternator body, and then threads into the rear of the bracket, where it is firmly locked with a 9/16" Nylock nut. The interior of the bracket is slightly longer than the mounting surface of the alternator, so you will need to put in a washer to shim the unit tight -- this permits further adjustment to keep the pulleys in one plane. A little torque on the hex-head bolt pulls the whole affair tight, with no play whatsoever -- there's no way this will ever develop the "wobbles" that plagued the old generator brackets!

The original adjustment bracket at the top of the alternator needed some offset on our car to work with the new unit -- ninety seconds with a bench vise and a sledge produced an official-looking "S" bend and a perfect fit. The securing bolt passes though this bracket and threads into the alternator; again, a very sturdy arrangement.

The old fan belt could be used over again, but wouldn't this be a great time for a new one? I thought so, anyway.

Wiring the new system requires splitting some sleeving on the wiring harness and some wire splicing -- you can either solder the connections or crimp on eyelets and bolt them together. You will need a battery cable with a built-in accessory wire on the positive battery terminal end. Other than that, there's enough wire in the existing harness to use over again with a little ingenuity. Workmanship is essential to both reliability and safety, so you need to work slowly and carefully when rewiring the car. Hooked up as per the instructions, the red "idiot light" is retained, and provisions are made for adding an optional ammeter if desired.

Our Amazon's lights are now significantly brighter, and the battery charges at idle, even under full load, dropping the idle RPM a slightly until full recharge is accomplished.

Now I can get on with thinking about adding that rear window defroster, an auxiliary radiator fan, fog lights, a four-amplifier stereo...

More info on the web:

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