Failed SW-EM Alternator Kits  

1-2008 R. Kwas

Statement of Guarantee
Policy for Broken Brackets
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Broken Alt Kit brackets:  Some kit failures have occurred over the many years I have offered them, but it must be stated upfront, that of the very limited numbers of failures of the mounting assembly of this kit which have occurred, every single one could be traced back to metal fatigue caused by vibration, which was in-turn caused by Failure Condition 1.  ...bracket not being tight against AND ONE WITH the engine block, OR the pivot bolt failure which has occurred, was similarly caused by Failure Condition 2.  ...the Alt not being securely captured AND ONE WITH the bracket.  There is no modification or improvement which can be made to the hardware to prevent either condition.  Both are a result of improper installation, and I long ago added the Tech Bulletins to the Sw-Em site and highlights in the instructions help assure a long-term successful installation.

Failure Conditions Considered:

Failure Condition 1:  The bracket MUST be securely bolted to the engine block using three 5/16"-18UNC X 3/4" long bolts.  The original bolts of the generator bracket, which are longer at 1" long (due to the original rubber shock mounts which were installed) may be reused, but a well-known cause of problems exists...it must be assured that these longer bolts do not bottom in the holes or exhibit excessive Run-In Torque before securing bracket (Run-In Torque is defined as  the resistance to turning a fastener into the threads of a nut or in this case threads of block, and before it is holding anything against the bearing surface of its head.  See also Run-In Torque).  Some variation in the hole depth exists from the factory, and also the amount of rust on threads or debris deep in the hole.  Both of these factors can and will affect the Run-In Torque of the bolts.  The simplest way to assure correct result is to first test fit the bolts into their holes without the bracket in place, and make certain that they thread in, without excessive run-in resistance, to a depth which leaves LESS THAN 1/4" of bolt shaft exposed.  Since 1/4" is the thickness of the bracket base, this will assure bearing surface on bottom of head of bolt will contact bracket, properly fastening it.  If necessary, clean the threads of the engine block by "chasing" with a bottoming tap or shorten bolts to 3/4" length.  Clean any debris from the hole (blast clear with shop air or simply a tube and a good exhale) and do not proceed with installation until the previous test is satisfied!  A medium grade thread locking compound or lock-washers should be used on bolt threads to prevent unwanted loosening.    

The other test which should be performed once bracket is mounted and bolts are torqued, is to try to spin the washers.  If it is possible to spin any of the washers, corresponding bolt has bottomed in its hole, or its high run-in torque has fooled installer into believing bolt is tightened against bracket, when it is in fact NOT, and it is NOT doing ANY holding of the bracket!  This condition must be corrected before taking vehicle into service or it will allow bracket movement and vibration which over the long term will cause material fatigue and failure.  All of these points are specifically covered, in SwEm Technical Bulletin No.1!    

Failure Condition 2:  The pivot bolt supplied with this kit is a first quality, extremely strong, thermo-forged, roll thread after heat-treat, socket head cap screw, made by Holo-Krome, and rated at 160,000lbs of tensile strength.  If a higher quality, stronger bolt is available for commercial (and not aerospace) duty, I'd like to hear about it!  Therefore, if this bolt breaks, you can be quite certain that there again was something very wrong with the installation!  On the single recorded occurrence of this, galling evident on the bolt sides after failure confirms that the Alt was allowed to vibrate against it, and this eventually caused material fatigue and failure. 


Pic of broken Pivot Bolt due to material fatigue as a result of vibration.  Galled areas highlighted. 

The nominal 2" length of the mounting boss of the Alt housing must be locked from pivoting and vibrating by tightening the pivot bolt.  Since the installer procures the Alt., this important conditon, crutial to correct mounting and long-term trouble-free service, must also be checked and assured by installer, and it is covered, in detail, in the kit instructions.  An additional spacing washer is included in the kit if the mounting boss is under-sized to take up this space and prevent excessive bending of the bracket to lock the Alt in place (see drawing).  This is also specifically covered in the Installation Instructions supplied with the kit!
 


Alt kit bracket showing alt installed and spacer washer.
 

Conclusions:  It stands to reason that if the bracket is ONE WITH the engine block, AND ALT IS ONE WITH the bracket, that after mounting, ZERO relative motion should be possible!  Therefore, after mounting bracket, fanbelt tensioning, and bringing all hardware to final torque, the Alt should not be felt to move if grabbed and given a healthy tug with engine OFF!  ...or be observed to vibrate relative to the engine in ANY WAY, and at any time while engine is running.  If it is observed to move relative to the engine in any way, it is not secured adequately and this condition must be investigated and remedied!  No improvement to the bracket design could prevent this as it is strictly an installation issue, so no change to the bracket is necessary.

Policy for Broken Brackets:  In light of the track record...that is, broken brackets have ONLY EVER been caused by installation issues, I will no longer send out replacement brackets at my risk.  I will only send out replacement brackets prepaid, and based on my inspection of the returned failed bracket, may share a certain amount of responsibility with you on it.  In one occurrence of bracket failure, and the ONLY time a vintage Volvo owner EVER screwed me, (Doug D. of Arizona, you know who you are, and anyone who contacts me about bracket failure can thank him for this policy!), was, when I immediately send him out a replacement for a bracket exhibiting a crack in the base plate (which incidentally failed after a year of service!  See Picture), and the failed bracket came back for inspection showing unmistakable evidence of having failed due to sitting on the engine block, vibrating for probably most of that year (Failure Condition 1), and Mr. D adamantly refusing to take even partial responsibility! 

Pic of cracked bracket due to vibration.  Galling on block mounting surfaces is unmistakable. 
This would not, and could not occur with proper mounting per instructions, Bulletins on SwEm site, and my repeated advisories!  I can only do so much...the rest is up to installer!

Statement of Guarantee:  One year to the original purchaser, given correct mounting.  Beyond that, subject to my inspection and judgment...and Iím a pretty reasonable guy!