First posted 6/2005 R. Kwas, additions on-going

Information for the well informed installer of the SW-EM Alternator Upgrade Kit
Comments added in Yellow.


Generator and Alternator Mounting Provisions on B18 and B20s
Special Applications
$40 Alternator Experience
Failure of (modified) Alternator Housing
...just install a "One-Wire Alternator"!
Minor Installation Error
Installing a 100A Alternator
Another $40 Alternator Experience 
Alternator Thermal Considerations

Alternator "R" Terminal
Delco Alt on OE Cast Bosch Pivot
One spacer washer fits between Alt Pivot Boss and Bracket, two don't 
Broken OE Alternator Pivot Bolt

Alt Kit Pivot bolt with a "Drunken Thread"!
Failed SW-EM Alternator Kits


Generator and Alternator Mounting Provisions on B18 and B20s
All B18 blocks had the three holes (Yellow) for securing Generator Bracket. 
Late B18s and all B20s added the (Green) Pivot for OE (Bosch and Motorola) Alternators.  This OE pivot is NOT suitable for mounting a Delco Alternator because of differences in the Alternator cases (see also Special Applications below). 

Picture of a B20 with both pivot and bracket holes. 

See also:  Broken OE Alternator Pivot Bolt


Special Applications

Mounting an o.e. Bosch alternator using the SwEm Kit bracket.  This situation has occurred twice - first, when the threaded mounting boss of a B20 block broke off (?), the bracket saved the day because it is secured to the block by the three threaded holes which were used on B18 block castings to mount the generator bracket, and fortunately were retained on B20 castings (although unused); and second , when a new Bosch alternator and (mechanical) regulator were already on hand, and didn't need to be purchased.  Since no mods to bracket were necessary in this case, the option still remains for a future upgrade to a higher output D-R alt. with internal solid state regulator.

The following mechanical differences between D-R and Bosch alternators exist:

1.  The Mounting boss nominal length of the alt. castings.  Bosch is shorter.  See Pictures 1 and 2.  Solution:  Use a spacer (or a stack of washers), sized to take up remaining space, but this spacer must be sized after cutting (Bosch) casting to correct for belt plane offset - See highlight on pic No.1 - once bolt is torqued, everything is locked from movement.
2.  The Pivot bolt sizes.  Bosch used a larger bolt than upgrade kit, so pivot hole in casting is larger.  When using smaller bolt from upgrade kit, this could cause misalignment.  See Picture 3.  Solution:  Use metal tubing or strategically sized and formed piece of sheetmetal to center pivot bolt in larger hole of Bosch alt., again, once bolt is torqued, everything is locked from movement.

3.  Belt Plane.  Different offset of alt cases.  Solution:  To make offset equal to that of D-R alt., and assure pulley alignment, cut away 3/8" of casting as highlighted in Picture 1.

Picture 1, Delco-Remy Alt. on left, Bosch on right.  Offset in mounting boss of Bosch casting which causes pulley misalignment is highlighted.

Picture 2,  Showing mounting differences from another angle (Bosch alt. on top).   Pivot boss length differences are visible.

Picture 3,  Showing mounting differences in castings and pivot bolt holes.


$40 Alternator Experience

posted by timbert on Wed, Dec 11th 2002 at 7:47 PM

I switched over to an alternator on my '66 122 - using the fabulous [WOW...Thanks! Ron] SWEM kit - several months ago. The one piece of advise that I didn't heed was to not buy the cheapest AC Delco type alternator I could find ... I bought one for $45 at the local auto parts super store. Everything seem to work okay for a couple months. For a while now, the alternator has been making quite a racket & the alternator pulley/fan looks to be wobbly - but everything seemed to still work & it has been awfully cold & wet & dark to be swapping out the alternator, so I just let it slide.

Today, when driving home at night - in a cold rain with wipers & fan going, the headlights seemed quite dim & then, when I switched into overdrive, the radio cut out momentarily. The amp light, however, never came on.

As I understand it, the amp light will light up if there is a difference between the voltage produced by the alternator and the voltage of the battery charge. So, my WAG (wild ass guess) is that the alternator is not producing enough amperage which caused the problems I experienced tonight.

Am I understanding the situation somewhat correctly? Are excessive noise & low output consistent symptoms of a faulty alternator ?

I realize that this is probably overly simple question, but I am trying to learn as best I can how to keep this thing going.

thanks for the continuing education


posted by
Ron Kwas on Thu, Dec 12th 2002 at 8:26 AM (amended and corrected)


That is totally typical of the $40 "rebuilt specials". If the alt was making serious mechanical noises that soon, it probably means that it didn't get new bearings when they "rebuilt" it...I wonder what else it didn't get...that's why I recommend paying for and installing the official AC Delco rebuilt ones...but it's your call of course.

As to the symptoms, dim lights indicate the alt is probably not putting out (loose belts and/or wires or that sort of thing notwithstanding), and the fact that the AMP light did not come on is somewhat unusual, but not impossible. There are some failure modes which do not result in AMP Indicator coming on...especially if you installed a "unknown" alt.

In the OE gen setup the AMP lite is connected as you state...but after the upgrade it is slightly different...then the AMP lite supplies the field power to start the alt generating power...after that, it "self-excites", so it could be putting out enough voltage to keep the AMP lite OFF, put NOT really putting out power.

Have you performed the "full field test" as described in the instruction? This bypasses the regulator and applies full field...if it doesn't put out then (indicated by system voltage rise - connect Voltmeter to monitor system voltage) that confirms alt is for s**t (which we kinda knew already anyway).

...bottom line is:  Remove alt, take to a competent automotive electrical place, have them check electrically, replace BOTH bearings and other words: Really Rebuild! OR, check paperwork I sent you with kit and buy the recommended alt.

Live and me now or pay me later...I told you so...close cover before striking... etc...etc...etc


... thanks for the kind words!

See also:  Another $40 Alternator Experience below.


 Failure of (modified) Alternator Housing                                                                                                              added 7/2010 

A simple solution is often the best solution, and simple should always be the goal, but beware of oversimplification!  Often, cutting away of part of the housing pivot is recommended as a simple way to allow an alternator to be used with the existing generator bracket.  Maybe some owners have had success with this, and their installation hasn’t failed (yet), but the fact is that removing part of the structure of the alt pivot is BAAAAD, it weakens the housing and cuts into the structural safety margin of the entire mounting system…if this is further combined with a mounting which allows any kind of movement or vibration, you can be fairly certain that the combination will let you down at some point!...and having cut the housing to fit it, surely killed any warrantee which you might need to exercise in the future.  Think twice before going the Quick & Dirty and oversimplified route…that’s really not why we drive these cars!

Shown below is a classic example of a failed Quick & Dirty alternator conversion…the (not so) clever installer simply cut away half of the pivot unceremoniously with what looks like a hacksaw, leaving a horrendous stress riser visible in the pic, (although it is also apparent that the stress riser did not cause this particular case), then used a bolt (which was likely too small in outer diameter), threaded along its entire length, including the part of the bolt which was in the pivot area.  This contributed to allowing vibration which shouldn’t have occurred in the first place, to cut remnants of these threads into the pivot inner wall, before eventually leading to the fracture which broke away what was left of it.  I wonder just how long (or short) of a time this installation lasted before it blew apart. 

The installer who did this work should consider switching careers to one which involves a shovel


WARNING:  Picture of a major hack-job, looking at which may induce vomiting, follows:

FIGURE 4.  Alternator housing, fractured at pivot which has been partially cut away. 
Also visible is evidence of vibration.  Picture credits:  Woodman

I warned you!  


The custom designed and fabricated bracket which the SW-EM Alt Kit is based on, will allow the installation of an unmodified Delco alt with a housing unweakened by cutting.  This means that the alternator housing retains its full strength, as designed, and it remains unmolested, giving the maximum strength to the mounting system, and putting the owner in a solid position for any possible future warrantee claims. 

LINK to “bad workmanship” thread on British Forum


"...just install a 'One-Wire' Alternator"!

[ I just had to reprint this answer to an e-mail question I received.]

A recommendation of "just install a 'one-wire' alternator" or similar is someone's quick, off the cuff, unconsidered, and incomplete advice, typically given to make the installation seem as simple as possible...

I can totally understand the appeal of this...I mean its pretty tough to screw up connecting just ONE lonely wire (not that it couldn't be done!)...but I have considered the details:  The AMP Indicator cannot function with a one-wire installation...and there are Alt. housing variations which must be considered given the wiring and alt location right next to the exhaust in the B18/20 kit has been engineered taking all these factors (and then some!), into careful consideration...and it is backed by literally thousands of successful if you're capable of following the explicit instructions included in the kit, and buy one of the specifically recommended, official, quality, Delco rebuilt Alts, and are capable of connecting THREE wires to the Alt., you will end up with a charging system in your vintage Volvo which has lots of electrical and mechanical operating margin, and which is therefore highly reliable...and also, an AMP Indicator which still functions, just like before! 

--------------- --------------------------------------------------------

Minor Installation Error:  Occasionally, like when an engine is apart for a while for a rebuild, someone might forget where things go when they put it back together, and get it this installer, who located the engine end of the Belt tensioning bar in the wrong (Red) upper hole in the head...we won't hold it against this installer (let those without sin cast the first stone!)...apparently he quickly realized the error and corrected it, by relocating the Bar securing point in the correct (Green) hole, but I thought it would be interesting to show here...  Funny thing is that the adjustment slot was even long enough to allow the incorrect placement. 

Belt tensioning Bar located in the incorrect upper hole (Red) in head, when it should be located, as before, in lower (Green) hole. 
Also visible is the pivot cast and machined into block for OE Alternators (Yellow) and new pivot (Orange) provided by SW-EM Kit bracket.

Correctly mounted Delco Alternator, including Belt Tensioning Bar...
Beautiful, and ready to render reliable service for a long time!


Excerpt from an e-mail asking about Installing a 100A Alternator:

I recommend not going above ~60A output, even with AC installed.  Track record with ~60A Alts has shown continued very good reliability (zero recorded failures as a function of output current!).  If you insist on putting in a higher power unit instead of one of the ones I recommend, you do this on your own...and YOU are then responsible for the engineering!   The Bracket will certainly take it, but you WILL need to uprate wiring, and definitely Fuseblock...and don't come back complaining to me when your Water pump pulley fatigues (from the additional possible cyclic load), blows apart, and possibly launches the Fan into the Radiator!  I don't want to be a naysayer, but remember, when strengthening the weakest link in a chain, the next weaker link will be exposed and vulnerable...!

Fatigued WaPu Pulley, possible the result of over-tightening Fanbelt,
but there is a good chance of this happening with a 100A Alt installed! 


Another $40 Alternator Experience:

My response to Andrew C 9/11/2016:  Shredding Belts on an Alt installation: 

The alternator is working fine electrically, but it is shredding belts. I have tried 3 so far, and have been very careful to tension them, the first 2 squealed horribly then snapped, the last one just gave up and dropped off somewhere, and the AMP light came on.

The angle of dangle of the pulleys relative to one another seems ok. The pinch bolt is nice and tight, tension seemed OK and the pivot was cinched up too.

What am I doing wrong? What would cause this?  My Response in Blue:  As a rule, Belt should be in a single plane, which obviously means pulleys must also be (it should be noted that Belts can take a LOT of misalignment...recall the 90degree turn with 90 degree axial twist of the 60s Corvair installation!), but I suggest you check this critically with a fresh eye again!...triple holes into block for Alt bracket are slightly oversized to allow some minor adjustment... but this is first time I've heard of multiple belts shredding themselves, so something is very wrong indeed!  It may be an possible misalignment of pulleys (although I fail to see how, unless something is assembled wrong, but I can't imagine what might be either!), or that one of the driven pulleys (WaPu, Alt) are sluggish to turn somehow (remove belt, check bearings in each for free turning ability) and at the same time, I'd also check all pulleys for imperfections on the belt running surface which might be damaging the belt (although minor ones of these would normally get polished away after a short while of running), but maybe a significant nick in pulley is insulting the belt every time it touches it, taking a chunk out of it, leading eventually to belt failure.  More likely, a squealing belt is caused by a very high (maximum) electrical load causing belt to slip...if allowed to persist, this will overheat belt and can lead to failure, as it has in your case (multiple times!)...what is State of Charge of Bat? ...have you charged Battery overnight with a line powered Charger? should!...expecting Alt to recharge a completely flat Battery (or a Battery with a shorted cell, which will continuously load the hell out of Alt) will result in a persistent high-Alt load condition which won't be doing the belt any favors, and can lead to these symptoms.  Also, CAREFULLY feel around (or look with an IR temp scanner) for hot spots in the elec system...all that elec energy generated under max load condition would be going somewhere!  That's all I can think of right now...  Again, if you wish to discuss live, you're welcome to call me today at XXXXXXXXX

I am going to take the alternator off tomorrow as it will aid me in removing the manifold, I will have another closer look at the bracket and see if the pivot needs packing or something.  Take and fwd a picture just off the plane of the belt to allow me a look, before removing.  I'd be quite interested in knowing and understanding root cause of this issue, as it is rare and preventative measures might need to be included on SW-EM site, or at least in Alt instruction.  Good Hunting!

Update:  The exact cause for the shredded Fanbelts was never determined by this it was, he returned the Alternator to the supplier who replaced it with another...when he installed the replacement, the problem was cured!  It should be noted that this WAS NOT an official Delco rebuilt unit, proving once again that you get what you pay for!


Alternator Thermal Considerations: 


Cooling air is drawn into the rear of Alt, past the electronic components, and is discharged out the front,
by way of the centrifugal impeller.  Green (A) is a threaded hole in Alt Housing.  It can be used to connect an addition Chassis Cable, and possibly to secure a Heat-Shield (see below).  Note the direction of rotation (yellow). 

I haven't had any reports of heat-damage to an Alt upgrade, so I don't think a Heat-Shield is necessary, but given the above, my recommendation for anyone considering adding such a shield would be to form it as shown here in yellow:

Heat-shield concept for Delco Alt installation:  Heat-shield (Yellow) would block warmer air plus radiation from Headpipe from rear of Alt while directing cooler air (Blue) from the front of Alt into the Cooling Air Intakes.  It could (and must be!) WELL secured by single fastener into threaded hole in Alt case (Green A).  It would be highly advisable to also use two additional securing points (Green B) at the Alt housing bolts). 

Note:  All advantages would be quickly negated if your groovy Heat-shield were to loosen and short the Alt output stud to chassis!

Link to Brickboard Thread:  Alternator Heat Shield:

While on the subject of Heat Shield and Cooling Air flow, here is a reference picture of a Delco Alt installation with an IPD header.  The hot exhaust is not too far away, but there's plenty of Cooling Air available given the general direction of the airstream and the hurricane of turbulent airflow occurring under the hood!   



Alternator "R" Terminal:

From FB thread about installing a Tach originally for a diesel powered vehicle with a W terminal on Alt ("R" terminal on Delco Alts):  

I agree that a Tach originally meant for a diesel (which has no Ignition System from which to take an RPM related signal) cannot be directly used to monitor RPMs on a gasoline powered engine, but understanding how it does work on the diesel, and a bit of engineering, allows using it on a B18/20! 

Calibration:  The only question in operating a former Diesel Tach in a different Alt would be the relationship of the frequency at the W ("R") terminal at a given RPM, on the original engine, versus the frequency from another Alt, and this would clearly be a function of the pulley diameter of the original Alt which the Tach played with vs. pulley Dia of the Delco.   

From those Links:


...and if the Alt does not have a W terminal (R for Relay on Delcos [don't ask me why!] cast into Housing), it can simply be added to one of the output phases as seen above!  Note that the "Bat" terminal (2) should more correctly be named:  Sense, to avoid confusion with Battery (output) terminal. 

Taking the Tach signal from the Alt also reminds one of early mechanical Tach drives, which would be taken by a speedometer-like cable drive from the Generator. 


Alt Kit Pivot bolt with a "Drunken Thread"!

Thread about installing a SW-EM Alt Kit:

My posting to that thread:


I realize this is an ancient thread, but I ran across it again while doing some research and wanted to chime in with a couple of stupid comments. First, a big THANKS all who recommended the engineered Sw-Em alt kit!

Advice often seen: "simply install a "One-Wire" Alternator..." that's oversimplified advice (it comes from people working on tractors, who apparently have trouble when working with more than ONE wire!), given by those who want to make it sound as easy as possible...what they don't mention is that when doing that, you also loose AMP Indicator function! If you can handle following specific detailed instructions, and connecting up all of THREE whole wires without screwing it up, that's the preferred way...and you'll retain the function of the AMP Indicator...just like before!

A couple of words about installing a 100A Alternator: First, a question: What would you possibly need that much power for in your car? Add up all the Loads (including the intermittent/occasional ones like Window lifts and Rear Window Defroggers) and you'd probably have trouble exceeding 1200W. And if you have a 1000W stereo installed, know that it draws less than 1/10 of that when turned up to make your ears bleed!...the only times it truly draws 1000W is on bass peaks, and they don't last very long (unless your showing off, in which case I probably can't help you!). If you want to supply bass peaks for a killer stereo, install some soup-can capacitors, and be done with it!

Also, those 100A don't come from nowhere!...they come from the engine...more specifically, the Crankshaft, by way of the Crankpulley, Fanbelt and (sheetmetal) [B]Water Pump Pulley[/B]...if you install a 100A Alt, in order to transfer that much mechanical energy through one belt (without squealing like a pig, if it's possible at all), you'll have to tighten up the Belt like that of a high-wire act across Niagara Falls...then you may get this for free: good luck!

...and I haven't even mentioned the wiring yet...remember...when strengthening one part, the next weakest link in the chain will be the one to break! If you simply want a reliable electrical system in your vintage Volvo, vigorous Wipers, WHITE Headlights, and a fully charged Battery with which to get started next time, I recommend and have engineered the kit to install a 60A Alt...then drive it like you hate it, knowing that it will likely be as reliable as thousands of customer miles have shown!



Delco Alt on OE Cast Bosch Pivot: 

Alt kit inquiry from Matt Y.:  (Comments added)

"... the (Delco) alternator that is currently installed on my 122 is using the cast mounting point (I call it the OE Pivot) on the B18 block.  It is out of alignment by 7-10mm, the alternator bracket is at the end of its reach and interfering with the alternator body so I can’t get the belt any tighter (it squeals on start up).  I’m curios if moving to one of your brackets would solve this for me and give me the clearance I need to get on a smaller belt?  The alternator is limited by the coolant hose when moved inwards. I’ve attached a couple of pics for reference." 

Matt's pictures used with his permission.  


Excerpt from my response "...the pictures...they show the misalignment (high, close to exhaust, and toward the rear, as apparent above in comparison of Alt housings), well, (at least installer didn't cut away part of the Alt housing to make it fit, see: Failure of Modified Alt Housing ) and yes the SW-EM Kit would absolutely cure all the issues (Alt position, therefore belt misalignment, adjustment range, interference) because it will relocate the alt a bit lower (as can be seen here:  SW-EM Alternator mounting provisions B18 and B20  )


One spacer washer fits between Alt Pivot Boss and Bracket, two don't: 

...from and Alt Kit Washer spacer issue email exchange...: 

From A.D.:  The alternator is loose within the bracket, but there is not enough space for two washers, so I can think of filing the mounting boss to allow for another washer or dismount the bracket and close it a bit, the play between the bracket and the alternator boss is less than 1 mm, but is enough to have it wiggle when the pivot bolt is fully tightened.

Response:  There is typically only room for installing one washer on a nominally sized [2 inch] alternator pivot boss, so its not a problem if there is not enough room for two washers. The remaining gap will be closed when tightening the pivot bolt. The intent of installing a washer is to take up excessive gap.

A.D.:  Unfortunately, the gap does not close after tightening, I guess that the remedy left is to put two washers, which will require a bit of filing on the alternator boss.  I have been following the Tech bulletin to the letter.

Response:  Again, the washer(s) are only present to take up excessive space...that's it!...if one washer fits, but not two, you could simply pry apart the bracket slightly (if possible...I realize the bracket is quite beefy and may not allow this)...or as you suggest, file the mounting boss slightly to make room for the second washer, or even cut another thinner spacer washer, or two, from a thin piece of sheetmetal (like even a soda can) and use that...I realize that coming from the aerospace world, you have been trained to follow instructions to the letter (and that is certainly good!!), as instructions have been authored by highly qualified individuals after much consideration (as have mine!), but in this instance, it's just not critical, and you may make a "judgement call" (you may not have an Airframe and Powerplant (A&P) rating, but in this case, its allowed!)...the important thing in the end when all hardware is fastened to final torque, that Alt is ONE with bracket, and bracket is ONE with engine, in both cases meaning that NO relative motion is possible.  [See below!]  

A.D.:  I filed a bit the alternator boss, added one washer and problem solved. 

Response:  Great! 


Mechanical conditions between Alternator Pivot Boss and SW-EM Bracket. 


Broken OE Alternator Pivot Bolt:  [This is not a failure of the SW-EM conversion, but of the OE arrangement with Bosch Alt, and demonstrates once again how important proper mounting of an(y) Alt is.]

A failed OE Bosch Alt mounting occurred, due to looseness of pivot bolt allowing vibration and failure of the (1/2"!!) pivot bolt.

[As I have noted before, the OE design is an "Overhanging Load", as mass of the OE Alt is supported ONLY on one side of the Alt housing pivot.  This is OK when everything is nominal and tight and no movement is possible.  If however the pivot bolt were to loosen for any reason (or not be properly tight in the first place), the system would be subjected to horrendous forces generated in the overhanging mass mode, on mount and pivot bolt, the vibration input being transferred by the Fanbelt, and in this case sufficient to eventually fatigue and break the beefy 1/2" pivot bolt!!  Alternately, I have also seen the mount on the engine block also break off (no picture, sorry)!!  This is much less so the case in designs where support is provided on BOTH sides of the pivot, as with the SW-EM design bracket. A double sided support design is therefore somewhat less susceptible to failure, AND also much more failure-tolerant if one were to occur!]

Where loose Delco Alts have caused failures, this shows that a loose OE Bosch can suffer under the same situation! 

Failed OE Bosch Alt mounting due to looseness of pivot bolt allowing vibration and failure of (1/2"!!) pivot bolt.  Note Galling, a sure indication that Alt was vibrating and not securely fastened!


Aftermath of a loose Bosch Alternator!  Even a 1/2" Bolt is no match for cyclic fatigue!
Picture by Vaughn H. and used with his kind permission. 

Link to Thread!&p=7293589#post7293589 

In the picture, circumferential galling is the unmistakable evidence of long-term vibration between two surfaces, and scarring at 4-7 O'Clock likely occurred just after final separation, when jagged edges of bolt vibrated against pivot. 

My comments to thread: 

"Such a failure is a rare occurrence, but not one which hasn't happened before...and galling apparent on the pivot from 1-4 O'Clock is clear evidence that pivot bolt or Fanbelt tensioning bar, or both were loose, allowing movement of the Alt, causing cyclic forces on bolt which caused breakage...there is certainly plenty of vibration input from the belt! Alternator should be checked to be absolutely secured to block and not being able to move in any axis...good practice is to check for secureness of Alt (and tightness of Fanbelt) any time hood is opened for fluid checking or other service.

On the Alt conversion brackets which I offer, the ONLY failures which have occurred on Alt housing, or bracket or pivot bolt, have occurred for the same reason: Looseness, and the fact that there was relative movement between Alt case and bracket, or bracket and block!  If Pivot bolt is properly torqued, after the Fanbelt has been tensioned, Alt will be securely ONE with block, and will stay that way!...but I include a nylock jamnut in my kit for additionally locking the pivot bolt in place (belt and suspenders...a triple safety feature, just because I can!). "


External material sources are attributed.  Otherwise, this article is Copyright © 2005-2019.  Ronald Kwas.   The terms Volvo, Bosch, A-C, Delco, or Delco-Remy, are used for reference only.  I have no affiliation with any of these companies other than to try to keep their products working for me, help other enthusiasts do the same, and also present my highly opinionated results of the use of their products here.  The information presented comes from my own experience and carefully considered opinion, and can be used (or not!), or ridiculed and laughed at, at the reader's discretion.  As with any recipe, your results may vary, and you are, and will always be, in charge of your own knuckles and future! 

You are welcome to use the information here in good health, and for your own non-commercial purposes, but if you reprint or otherwise republish this article, you must give credit to the author or link back to the SwEm site as the source.  If you don’t, you’re just a lazy, scum sucking plagiarist, and the Boston Globe wants you!  As always, if you can supply corrections, or additional objective information or experience, I will always consider it, and consider working it into the next revision of this article...along with likely the odd metaphor and probably wise-a** comment. 


B A C K ! . . .to Tech Articles Index Page