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Old 02-09-2009, 12:14 PM   #1
jpowell1
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Default 940 100A Alternator Swap in '82 240

I just want to throw this out there so it'll come up in a search for other people who do this. The info I found on this swap was kinda spotty, and I tried a number of searches.

I swapped a 100A Bosch alternator from a 940 into my '82 244. The 940 alternator came with the bracket to mount the alternator on the driver's side on the top of the engine. My alternator (55A! what is this, a Model T?) was on the passenger side on the bottom. I have a water-cooled T3, and then metal oil lines to an oil cooler for the turbo. (Leastaways I'm pretty sure that's what those are...)

Biggest Issue: The 100A alternator is a beast in comparison to the 55A. It would fit without bending the metal oil cooler lines, but I could not tilt it up enough to make the stock 36.5" belts fit over the alt. pulley. The 100A alternator kept hitting the exhaust heat shield and the wastegate actuator diaphragm housing when I tried to tilt it up. Since you have to lay it way more out to the side to make this work, it means everything is now too short. That means the stock belts are too short, the stock charging wire and battery light wire are too short, and the stock bracket is too short.

Belt Solution: I used a 38.5" belt. I couldn't quite get a 38" belt on there. Maybe if I tried harder I could, but meh. A 38.25" would have been perfect. It was a 15/32" cross section (11mm) by 38.5" length, labeled 15385 at the Zone or other parts stores. Make sure you get the same brand on both belts. I got two different brands (lots of stores only carry "one" of each) and the lengths are a little different, despite the identical labels. If one is shorter than the other, PUT THE SHORTER BELT ON THE PULLEY GROOVE CLOSEST TO THE ALTERNATOR BODY. Trust me. When these belts are tightened, then are very, very close to the lower alt. mount bracket, and the belt closest to the alt. body runs right over the top of it. That belt needs to be tight, so put your smallest belt there. The groove that's further from the alt. body puts that belt out away from the mount so it is not an issue there. But if you put the loose belt on the inside, it'll rub and then it's game over.

Small Wiring Solution: I was able to reuse the same ground wire ring terminal. Make sure to put an 8mm backup wrench on the nut closest to the body if the top nut doesn't wanna come off; you don't want to break that stud. I know some people have to change this, I did not. For the thin red wire (that goes to the battery light, I think), just cut a ~ 4" piece of thin wire, put a spade on one end, and then the female spade on the other end, and that'll extend the thin wire enough to go on the proper terminal of the alternator. Some people have mentioned that they had a ring terminal there, so you may have to modify this wiring a little. Bottom line is you'll need maybe 4" or so to make this thin wire long enough. If you are smart enough to change an alternator, you'll know what has to be done here.

Heavy Wiring Solution: This was sort of a PITA, but it got done. The stock charging wire will probably be TOO SHORT. Do not just try to hook it up and pull the wire taut. Electrical connectors .ne. mechanical connectors, so don't do that. You will need at least an inch or so extra. Mine was just BARELY short, but don't succumb to temptation here. My charging wire was 8ga. Do not use a smaller wire (higher gauge number). You will need something to splice in a longer piece of wire. You can use a lawnmower battery cable (6ga at the local Zone) and cut one end off, since it has a good ring terminal already factory crimped on one end. Just drill out the hole for 6mm (or 1/4" here) and then you need a way to connect the other end to the stock charging cable. I had a 6mm ring terminal on my stock charging wire. You can purchase heavy gauge connectors from a local electrical store that have a hole with a setscrew to attach to bare wire, and then they have another hole where you can bolt them to something. I used a 12mm long M6 bolt and double-nutted the original wire to that type of connector (with a lock washer, too), and then put two layers of heatshrink (big heatshrink!) around the whole joint. I used roughly 6" of wire. The other end just bolts right to the alternator then. The reason I made it longer was so the wire could just kind of float freely behind the alt. and not be stretched or rubbing against anything.

Bracket Solution: I levitated a 13mm wrench with the power of my swearing at 9pm when I realized the bracket was too short. Since you have to lay the alt. out so far, none of the stock brackets are gonna reach. I just took a spare bracket, cut the slotted part out, and bolted that to the stock old 240 upper alt. bracket so that I could extend the slotted part. I used two M8 bolts to bolt the "extension" on the existing bracket so it couldn't fold up under compression from the belt tension and then this all worked. You need to extend the slot in the bracket about 2" or so. Recycling another alt. bracket worked for this. As far as the order goes, the stock 240 alt. bracket is bolted onto the block, and then the extension piece is bolted on the *front* of that, I am pretty sure (towards the front of the car) and then the front face of the extension mates with the *back* of the upper alternator mount on the 100A 940 alternator. Since I recycled the stock bracket I could use the stock M8 carriage bolt and I only had to tighten one nut on the front to hold it all tight.

Conclusion: If you know this crap beforehand and round up these parts BEFORE starting, this job is easy. I spent at least 8-10 hours figuring out how to extend the wiring and the brackets, as well as figuring out exactly what size belt I liked. If you get the parts before you start, this shouldn't take more than a couple hours.

If you would like for me to sell you the parts to make this work, I can do that. ;) But you ought to be able to do this.

I can now run my blower motor, high beams, both seat heaters, and my wipers and stay above 12V. It's nice. I am planning a headlight upgrade soon and needed the juice. The new alt. runs at ~ 14V all the time until you load it, so it was a big improvement over stock. Please add any commentary to the thread, or stuff that will make it easier for someone else.

I am sorry I have no pics, but my camera battery was dead and I can't find the charger.

Final Note: I did not personally have any problems with the oil pressure sender. I have a small fitting in the block that tilts the oil pressure sender up 45 degrees and kind of away from the alternator. I am not sure if that is necessary for this, so be warned.
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Old 02-09-2009, 05:28 PM   #2
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i put a nippon denso 100A alternator in my brother's '83 242 (b21ft) and all i had to do was change the terminal on the charging wire, and put some washers on the tensioner bolt to shim it up.
worked great. only problem we had was the first alternator we tried had an effed regulator and would put out ~18+ volts at times.
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Old 02-09-2009, 05:35 PM   #3
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Quote:
Originally Posted by HonestJhon View Post
i put a nippon denso 100A alternator in my brother's '83 242 (b21ft) and all i had to do was change the terminal on the charging wire, and put some washers on the tensioner bolt to shim it up.
worked great. only problem we had was the first alternator we tried had an effed regulator and would put out ~18+ volts at times.
Same but no regulator problems. Mine still works to this day. Been on two motors with no problems
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Old 02-09-2009, 05:37 PM   #4
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the nippon one is lovely and small
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Old 02-09-2009, 05:38 PM   #5
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This alternator install is for the large Bosch type that looks like a large Denso alternator correct? I just wanted you to clarify which Bosch alternator it is. It's the type that has an internal fan and internal regulator. That's the largest hardest to fit alternator that are direct fit alternators. The Denso and older style Bosch alternators fit a bit easier.

A good writeup with good descriptions of what you did.
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Old 02-09-2009, 05:44 PM   #6
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would love to see some photo's of it. i put the 80amp 760 one in my 244, that was a tight squeeze on the stock belts/wiring etc
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Old 02-09-2009, 06:36 PM   #7
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So there's one that fits better...that is good to know now that I did everything. lmao

It was a large Bosch, the voltage regulator is external, I am pretty sure, just bolts onto the back of the regulator. I was able to reuse the voltage regulator from my old 55A alternator since it was fresh.

The fan must be internal; the pulley did not have any fan blades on it and the front face was just flat. I will try to get some more info on that. If I can get the camera charged I'll try to get some pictures of it. Maybe the buddy who pulled it for me will remember more about it. :D
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Old 02-09-2009, 06:55 PM   #8
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I had easy time swapping in the 100A on all of my Redblock engines. Be sure you Add another ground wire, preferably 4 gauge. I went with 2 gauge and noticed everything got brighter and the alternator had a way easier time keeping 14v. The stock 240 alternator ground wires often fail and cause charging problems or other problems. Espicially on the turbo models with the extra heat.
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Old 02-09-2009, 10:30 PM   #9
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Hey, good tip on that, thanks!

It was the larger Bosch unit out of an early early 940 according to the source.
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Old 02-09-2009, 10:57 PM   #10
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Yeah mind was earlier one with external regulator and external fan
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Old 03-21-2009, 06:46 PM   #11
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Just get the brackets off of a 7 series volvo for the alternator and also get the bracket for the power steering pump (with all the lines goin to the rack) then swap the position put the alternator on top and the power steering pump on bottom

the brackets mount right up to the block
and the power steering pump will be able to stand the heat better

although if you decide to do this the A/C has to go and
u have to get a larger belt to go from the alternator to the pully
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Old 12-22-2013, 10:00 PM   #12
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What if you have a 100amp from a 940 going on an 88 244 like I do? The 100a has only 2 studs for wires, the B+ thicker one and only 1 little stud for an 8mm nut, I've read its to the dead battery light, I believe. Also, the 100a unit has the black cover on the terminal side unlike the oem 80a. They're both Bosch. Can the thinner wire with the shortest reaching distance be cut and turned into a female space for the leftover connector on the alternator? What are they for? WHAT DOES IT MEAN!? WHAT DOES IT MEAN!?
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Old 12-23-2013, 05:10 PM   #13
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The "dead battery light" also is the alternator exciter circuit, I believe. If this isn't hooked up, your alternator will not function until it self-excites by revving to well over 2000 RPM. I know this because my battery dead light stopped working in my 940 thanks to a cracked gauge cluster circuit board. Resoldering the board fixed the problem.
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