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  • Mechman Alternator Installation

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    My OEM alternator in my 2002 Cummins Auto was producing high AC voltage occasionally during very hot days and was causing my transmission to shift improperly (see Torque Converter Lock Unlock Issues).  Many of us have had this problem and have tried many different remanufactured alternators to varying degrees of success.  As noted in the torque converter article, AC noise is going to come from the diodes in the rectifier failing or failed solder joints in the alternator.  

    Heat and load is generally the cause of electrical component failure.  The heat can kill the diodes themselves and also damage the solder joints on the circuit boards.  Heat can come from high power loads on the alternator like extended use of heater grids, high wattage aftermarket inverters or accessories, and also normal use during extremely hot weather.  Load can be normal electrical loads, but load can be unintentionally increased by deteriorating grounding or poor electrical connections.  It isn’t uncommon to see cables and corrosion on our old trucks and grounding alone can cause high intermittent resistance that can burn out electronics.  

      (Note: all of my tests were done with a Fluke 115  multimeter.) 

    • From Mopar Man's article, we know we should not see more than 0.1 VAC from the alternator.  
    • Ideally, VAC should be as low as possible.  Some noise is impossible to eliminate, but there should not be much.
    • My original alternator voltage was 1.3 VAC max at higher RPM and 0.040 VAC max at idle.  Occasionally on really hot days, the truck would really act up and I am convinced that it was higher than this, but this is the highest I registered as I didn’t have the meter on it all the time. 

    Needless to say, I needed a new alternator.  I decided to give Mechman a try.  It was expensive, but I don't really have time to mess around as I am on the road and away from home for an extended period.  Mechman is known for heavy duty high output alternators commonly used in very high output car audio systems as well as marine engines.  They advertise some pretty amazing numbers on youtube, have impressive made in USA parts, hairpin stators and solid copper rectifier plates with up to 300% more heat transfer capability than stock.  Mechman advertised the unit I purchased as being the same unit they sell for Cummins Marine applications and have yet to have one unit returned for overheating.  Plus, the alternator is also supposed to be capable of putting out more power at idle than the OEM alternator at RPM.  All sounds good, right?  I also bought the zero gauge cable kit, to make certain that at least the alternator is grounded.  More on the cable kit below.

    Final Results:

    • Mechman Alternator was showing 0.025 VAC at idle and 0.051 VAC throughout the RPM range.  
    • Time will tell if this alternator keeps up, but overall I was impresed with how it runs.  The transmission shifts far far better than it ever has, even with the VAC within limits.
    • I did request a OEM sized pulle on the unt, which must have been overlooked by Mechman.  I don't doubt they would fix this, but I have decided to give the smaller pulley a try.  

    The kit, as delivered...  And yes, I know the engine is a bit dirty.  New cables and a wiring clean up is in the works. 

    Front of the alternator, note the smaller than factory pulley.  I am getting some squeaking on shutdown due to the pulley and will end up getting a new smaller belt soon.  I will update if I find a good solution to this.  Mechman does this to get more power at idle, and advertised more output at idle than the factory alternator at peak RPM.

    Mech alt front


    Rear of the alternator.  Note the copper plate and copper output stud.  A note about the stud, it doesn't fit the cable connectors included in the cable kit I bought, but the cable kit is easily drillable to the correct diameter and I found no problem with this minor "modification" required. 

    Mech alt rear


    Accessories in the Alternator box, not required for this installation. 

    Mech accessories


    Cable kit, cable on left, connectors on the bottom, fuse zip ties and heat shrink on the right.  

    Mech cable kit


    Below is the cable and fuse.  It is a simple system.  I used the zip ties to keep a little tension on the cable as I fed it into the connector.  You cut and install the connectors yourself.  It wasn't that difficult, just remember to measure twice and cut once.  I still have enough black cable to make some additoinal grounds for the truck and I only used 4 connectors.  



    I ordered the 170 Amp alternator that isn't advertised on their site.  You can call Mechman and ask for special stuff, and in this case, 170A is more than I need and cost less than their 260A model.  Mechman also runs a slightly smaller pulley to get more RPM from the alternator.  I was able to run the OEM sized accessory belt on my truck after the swap.  However, I do think that I will need to find a slightly smaller sized belt eventually as the OEM sized belt squeaks a little when I kill the engine. 

    I opted for Mechman's 1/0 Zero Gauge cable kit.  This kit is overkill.  I love overkill when it comes to key systems like primary electrical and fuel system.  These cables could carry a lot more power than my 170A alternator can put out.  Chances are you could make your own kit for less money from a welding supply shop or good auto parts shop.  The kit included two lengths of cable, some really great adhesive backed heat shrink, connectors, and a decent 170 A fuse.  The idea here is to eliminate the resistance between the ground, battery, and the alternator.  Resistance causes heat, and the less heat I have the better and longer this system should work.  The factory small gauge wiring is suitable for OEM loads and the battery lead (positive lead from alternator to battery) should still be enough... But the OEM ground is inadequate in my opinion even for OEM alternators. 

    Here is the OEM lead to the fuse block & battery.  Puny steel connectors running from alternator field to fuse block to battery.  

    OEM wiring

    Mechman leads, which bypass the fuse block with a separate fuse straight into the battery... 

    Mech alt inst

    When this system is ran this way, it bypasses the 140A factory fuse, below in red. I disconnected the fuse and kept the fuse just in case I need the factory wiring, which I kept zip tied out of the way.  Removing this fuse de-energized the OEM field wire.  This post also makes a nice in junction box 12V unfused battery tap that I plan on using when I clean up my wiring and replace the battery cables.  

    Fuse block

    All in all, easy install, good parts, and hopefully... Peace of mind.  If the alternator fails or I have any trouble with it I will update the article.  Sofar so good, one month in as of 1/16.  

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