Alternator conversion
-Written by Steve Phillips for Hot VWs magazine-
In this article, I want to talk about doing and alternator conversion on an upright engine. That meaning all Bugs, Ghias, Things, and Buses up to 1971. Is an alternator the way to go? As with most things, there are pros and cons to having them. Can I put an alternator on my engine and is that the way to go? I’ll explain my opinion and let you come to your own conclusion.
From my experience, generators are more reliable than alternators. With a generator, you can jump start, push start, and basically abuse them. They just keep working. Alternators are a little more sensitive. If you jump or push start, you run the risk of killing the alternator. That means you’re buying a new one. It’s not a given that you will ruin it by doing those things, but it does happen. It has happened to me a few times and usually not at a good time. For instance, being at a show out of town! So why even go with the alternator? Here are my base criteria: Will this car be needing a lot of amps? Maybe a Baja bug with lots of lights? Streetcar with a big stereo? Camper bus with lots of gadgets? If so, then yes, an alternator is the way to go. A standard generator puts out 30 amps and a normal alternator puts out 50. Another reason an alternator might be the way to go is if you’re converting a 6-volt car to 12-volts, then, it's simple when it comes to the wiring. How so? A 6-volt generator has the regulator mounted on top of the generator and the wires go right into it. On 12-volt generators, they have a remote regulator and that will have to be mounted somewhere and new wires made to go from it to the generator. Please just make sure you don’t mount the remote regulator to the fan shroud with self-tapper screws. It will fall off and short the whole main harness. Remember, the hardest thing about doing electrical is getting the smoke back in the wire...Just kidding. An alternator has the regulator built into it, so your wiring stays right where it was on the 6-volt generator.
The only other exception to putting an alternator on an upright engine, would be a 36hp motor. The reason being, on a 36hp motor, the stand that mounts the generator does not come off the engine. Alternators are larger than generators so the stand (mount) will not fit. If you have a 40hp-1600hp, then you’re in luck because the stands are removable. There are three types of stands: 6-volt, 12-volt generator, and 12-volt alternator. As stated before, the 6v stand is smaller in diameter than a 12v generator or alternator so to convert to 12v, you will need a 12v stand. In addition to the 12v stands, you have those specific to generators and those for alternators, as well. Here’s the dealio; the alternator stand is a narrower width (front to back) than a generator stand. This is because the front part of an alternator is larger. A generator is the same size in diameter all the way from the front to the back. So, you can put a generator on an alternator stand but you cannot put an alternator on a generator stand. You might need to read that again. With that said, if you’re converting, look at what you already have before going out and buying parts. There is a chance you already have the correct stand!
So how do I perform this conversion? There are few ways to go about it. First thing you’ll need to do is get the generator off. Looks easy, but it’s not. If your motor is out, it’s easier as we will at some point need to get the nut off the back that holds the fan on. If the motor is in the car and you don’t want to take the motor out, there is a little trick that you can try. First, disconnect the battery. The wire that goes to the regulator is unfused power and we don’t want to short this wire. With the belt and everything together, grab a 36mm socket, a ratchet or breaker and reach around the back and get it on the fan nut. Next, with a screwdriver, place it in the notch of the pulley (as if you were going to take the belt off). This will help to keep the generator shaft from spinning. Now, you can try to break the fan nut free. If you get it, you’ll be ready for the next steps. If you cannot (because someone put in on with an impact), you will have to pull the motor or pull the fan shroud up. Pulling the fan shroud up on a non-doghouse fan shroud is not the end of the world. Pulling it up on a doghouse shroud IS close to the end of the world. You’re better off pulling the motor out, which we will get into later. Okay, so you’ve got the fan nut broken free and it’s loose. At this point, you’ll want to remove the belt and the strap that holds the generator to the stand. Onto more fun, you will see 4 bolts or screws (factory were bolts) that hold the large circular tin on that is attached to the generator and fan shroud. These will need to come out. If you have a single stock carburetor, remove the carb, and put a paper towel in the intake where the carb was. Getting the top two out is no big deal. Getting to the bottom ones... not so easy. If they are bolts, you can squeeze a wrench down there and unthread them. If you have screws, get ready for a huge pain in your a**. That’s why the factory used bolts here. Once you get them out, you’ll need to reach around the back and unthread the fan nut. You will also be removing a large wave washer that is under that nut. Now, put your hand on the fan and spread your fingers out and wiggle the fan until it starts to come off. With your other hand, pull the generator towards the rear bumper. What we are trying to accomplish here is getting the generator out and leaving the fan in the fan shroud. There isn’t enough room to take it out as one unit. Once the large circular tin hits the intake manifold, the fan should be free of the shaft, and you can just tilt the generator out. Give yourself a pat on the back, the hard part is over!
If the motor is out of the car, you can pull the fan shroud up. You can start by removing the belt and generator strap. Next, there are two bolts/screws (one on each side) where the fan shroud meets the cylinder tin. If this is non-doghouse shroud then just lift and the shroud will come right up, with the generator attached. If this is a doghouse shroud, there are a couple of tins on the back side of the shroud that will need to be removed to lift the shroud up. Once you have the shroud out of place, lay it on its back and remove the four bolts/screws that hold the large circular tin to the shroud. Once those are off, you can lift the generator out. As you can see, the process is significantly simplified by having the motor out of the car.
Alright, we have the generator out. What’s next? I would start with the generator stand. There are four 13mm nuts holding it into place. Remove them and the stand will come off. Once that is off, we need to think about the oil filler. There are a couple of things we can do when it comes to this. One way is to clamp it in the vise, get out an oil filler spout tool (special tool), and remove it so we can install it on the alternator stand. Keep in mind, there is a gasket, and it goes between the stand and the filter spout, not on the inside. A single port intake gasket will work if you don’t have the correct gasket handy. The other option is to buy an aftermarket oil filler spout. I like the stock ones, but that’s just personal preference. The after-market ones don’t have the baffling that a stock one has. Either one will work. Now, to reinstall the stand! There is a baffle under the stand. It is important that it goes on in the correct way. This baffle keeps oil that is thrown up by the cam gears from shooting up the oil filler. I see them installed incorrectly all the time. Please see picture for correct way. The correct stack up of gaskets is paper gasket baffle then another paper gasket. I use Gasgacinch gasket sealer on the paper gaskets and the torque on the four nuts is 15 lb.-ft., but snug works too.
Now, we are going to look at things for those of you who are converting from a 6-volt to a 12-volt. Unfortunately, there is very little we can use here. You will use the fan, fan hub, hardware, woodruff keys, pulley shims, nut, belt, and shims. You will need to buy a 12-volt pulley, 3 piece backing tin (circular tin), and a strap. To begin the assembly process, I start with the 3-piece tin. There is a correct way to put the tin on so make sure you are paying attention. Start with the flat piece and if it has a ½” hole in it, when holding that piece vertically, the hole should be facing down. Stack that onto the two studs that stick out of the back and then position the small round piece so that it is cupping the flat piece. As for the second tin, look at the edge. You'll see it has an open area and that open area faces down, as well. Now, install the two nuts. I use nylocks for these or you can use a small drop of blue lock tight on non-nylock nuts. We don’t want them coming off; however, do not over tighten them, we just want them snug. Now, place the woodruff key in the slot of the alternator for the fan hub and install the hub. Make sure you're not pushing the key out and then install the fan. If the motor is still in the car, this will be a mockup. If the motor is out, we will be installing it for good. Moving forward, you can put the fan on the hub with the wave washer and nut. Hand tighten this nut and give the fan a good spin. If it hit the tin, you will need to shim under the fan with a pulley shim. Keep playing with this until you have the fan spinning completely clear. Try not to shim it too far away from the tin though because if you do, the fan will hit inside the fan shroud. With the fan on, stand up the alternator and install the pulley woodruff key and the inner half of the pulley. Pick up the alternator and give the fan a spin again. Does the pulley clear? Most of the time it will. If it's still hitting, you will need to take it off and sand the back side so that it doesn’t. That completes the setup process. If you have the motor out, go ahead and install the alternator assembly in the fan shroud with the fan shroud laying on its back. Install the four bolts. Rule of thumb: if you have a stock intake manifold, use a bolt (6mm by 1.0P by 10mm long, with a washer), if you have dual carbs, screws or bolts work here. Tighten them snug and spin the pulley. Do you hear anything rubbing? If you do, you will need to play around with shimming the fan again until you don’t. If you don’t hear any rubbing, then you're good to continue putting the fan shroud back on. If this is a non-doghouse oil cooler, you're okay to just put the shroud back on. Make sure the fan shroud goes on the inside of the cylinder tin on all edges. Install the two side bolts and leave them loose. Now, install the strap around the alternator and stand and tighten it. Again, give the pulley a spin. If everything is clearing, you can tighten the side bolts snug. If you hear rubbing, loosen the strap, and wiggle the top of the shroud in or out while spinning. If you find a spot where it doesn’t rub, tighten the strap there. Again, tighten the side screws. If this is a doghouse shroud, you will want to make sure there is a foam seal on the oil cooler from front to rear. This keeps the air going through the cooler and not around it. Make sense? Once back on, put your two rear exit tins on.
Now, I'm going to address a scenario where you have the motor in the car still. If you don’t, stay tuned anyway. What you're going to do is take the fan back off the alternator keeping track of any shimming you might have done. Place the fan back in the shroud and tilt the alternator back into the fan shroud. With it sitting there, reach around the back and line up the fan to the fan hub. Once it’s in place, put on the wave washer and nut. Pay close attention to the wave washer as we want to make sure it goes onto the fan hub correctly. You won't be able to see any of this so you will have to feel your way around. Tighten the nut as much as you can by hand and push the alternator back into the shroud all the way so the four bolt holes in the circular tin line up with the four holes in the shroud. Now, install your bolts/screws. Again, the top ones are a piece of cake. The bottoms ones, not so much. Especially, the inner lower. I've tried ample things to simplify getting that bolt back in there, but there isn't an easy way. Once you have that on, go ahead and let out a big yahoo! I flippen' did it! After you're done dancing around the garage, you can put the strap on and the belt. On the belt, please read my article on the pulley throw competition. All I'm going to say is you must have a minimum of 8 shims no matter what. What you don’t use between the pulley halves, you will use on the outside. Once the belt is on, grab your torque wrench, set it to 40 lb.-ft. and torque the fan nut. To do this, put a screwdriver in the back half of the pulley like you would have done to get the belt off. For those you who had to pull the motor out because someone used an impact gun to tighten it the last time, this is why we torque it.
We've covered most of what you will need to complete this conversion. Lastly, we will go into the electrical part. More than likely, you got an internally regulated alternator (all the new ones come that way now). If you have a 6v car, then you will be putting the two large red wires to the post (stud sticking out of the alternator pointing straight up). I crimp an eye electrical end to each red wire then put those on the stud and tighten the nut. You will see a small, blue wire. That is your field wire. That will push onto the male end that is sticking up. BOOM, done. If your car was 12v, then we are going to have to bypass the voltage regulator that is under the rear seat. What you want to do here is hook the three red wires together. I crimp on female ends and use a two to one connector to do this job. Please don’t twist them together or use a house wire nut. Just so you know, it will be the two red wires that were on the B+ terminal and we are hooking those two red wires to the red wire that was on the D+ terminal. Now, we will take the blue wire that was on the #61 terminal and hook it up to the green wire that was on the DF terminal. You can do that by using a one-on-one junction. You could use a butt splice, but as the name infers, it’s a butt splice. I would rather use a one-on-one. The brown wire you can leave alone, that is the ground.
To conclude, hook your battery back up and start the car. Make sure your idiot light goes out and that will let you know its charging. One last note here, if your idiot light is not hooked up or the bulb is out, the alternator will not charge. What? Are you kidding me? Yep, that's right. So let me explain what's happening. When you turn the key to the “on” position, the power goes through the idiot light and back to the push on connector on the alternator. That connection does two things. One, it’s a ground when the alternator isn't spinning, so the light comes on (power and a ground will light a light bulb). Two, it puts a little bit of power into the field part of the alternator which we call exciting the field. Now, start the motor. The field is excited, and the alternator will now produce power. It is putting power into the field wire and the light goes off. Why? Because having power and a power will not light a bulb, hence the light going out. If you don’t excite the field via the idiot light, the alternator will never start charging. I can't tell you how many customers have come in wanting a new alternator because theirs have stopped charging and it was a $1.00 light bulb that burned out. Also, those of you that installed the “mondo” 90amp aftermarket alternators, it's not uncommon to have to rev the motor up a bit to get the light to go out. That’s normal.
The key takeaway here is if you have a car that doesn’t need a lot of power/voltage to run miscellaneous features, stick with the generators. If you do have a need for that extra voltage, it would be wise of you to go to convert to an alternator (unless, of course, you enjoy being the last one parked at the car show because your car won't move). That’s all, folks! You're ready to roll. I hope this article helped you in making an informed decision.