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Mounting a different alternator ~ any alternator ~ other than the Original Equipment Lucas requires some thought about how the loads applied to the pulley of that alternator will be transmitted into the OE mounting points, should you choose to use them.  The Bosch/Saturn units I discuss here have the advantage of being virtually a "drop-in" replacement/conversion for the OE Lucas units and work with the original mountings as designed.  Other styles of alternators don't always lend themselves to using these mountings in the manner they were originally intended, and sometimes minor disasters have occured as the engine torque transmitted by the drive belt has applied forces in directions they were not designed to take.  This becomes even more critical as higher output alternators are used, since they require more engine HP to generate more electricity when push to their highest output campacity (we don't get anything for free, unfortunately) and that means the forces applied will increase, and sometimes, beyond what even the OE installation was designed for.

My advice is to carefully review the experience of those who have done ANY conversion.  You may find, as I have, that some are better thought out than others.

Cheers,  Bob Muenchausen



Please go to Barney Gaylord's excellent MGA site!

http://mgaguru.com/mgtech/electric/ac101.htm



"MGB Electrical Systems , An Essential Manual"  By Rick Astley, an MGB enthusiast and automotive electrical engineer, is one tool you should add to your MGB's technical library. You can find a copy at Little British Car Company, http://www.lbcarco.com/   It covers the whole MGB electrical system, including Alternator Conversions as well as stock alternator systems and is well worth having as you undertake one of these conversions or attempt any other electrical work on your MGB.

Plainly understood wiring diagrams for MGBs ~ Also, I highly recommend getting your wiring diagrams from Dan Masters' website at http://www.advanceautowire.com .  You can download these, take them  to your neighborhood Kinko's or the like, have them enlarge them and then laminate them.  Much more clearly understood than the diagrams shown in most any other manual.  And, when laminated, your greasy fingerprints are easily wiped off !

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Two alternator conversions have emerged over the years as being very good and reliable alternators, and which present the least amount of hassle for the owner to do themselves. 

About 10-12 yrs ago, a Bosch alternator as used in the old late 70s~early 80s Ford Fiesta, was presented as a good option as it would mount in essentially the same manner as the OE Lucas units, and had the advantage of somewhat higher output than the 16AC and 16ACR alternators in use on MGBs from 1968 to 1974.  This became a pretty popular conversion. 

However, as the last decade has progressed, other folks have proposed using others, and one that also became an instant hit for similar reasons was the early 90s Saturn Alternator.  It produced much more current than either the Fiesta Bosch unit or any of the OE Lucas units and seemed ideal for folks who were adding some creature comforts or high powered car audio to their MGBs.  The Saturn unit also has come to be far more readily available than the older Fiesta alternator on the rebuilt market, and so, it has become the current conversion of choice.

The information that follows covers both the Saturn alternator and the Ford Fiesta Bosch units.  The Saturn information was originally compiled by Daryll McLendon and I present it here for informational purposes only as his webpage on this conversion vanished some years ago. The Ford Fiesta Bosch alternator conversion is my own work and I have chosen to leave it here as both an alternative and as a reference for those who have installed one of these alternators on their cars sometime ago or inherited a car that the previous owner had made this conversion to.

 I would suggest that the Saturn Alternator conversion is preferable at this point in time for anyone wanting to change from a Lucas alternator setup, as we are witnessing the supply of Fiesta alternators drying up.

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From {the previously existing} ONE FAST MGB {website} 
Author:  Daryll McLendon

Imagine sitting in your MGB at an intersection on a cold dark night (headlights on, brake lights on, heater fan on high), in a driving rain (wipers on high), listening to your favorite song playing from the CD changer on your stereo system and having your directional signal blinking away indicating your intention to make a left turn.

You can do this and not even think about how long it's been since you've last changed your Lucas alternator.

It can be done with little out of pocket and an hour (more or less) away from driving your "B".

A 1991-1995 Saturn 11 C-amp alternator will, with a few modifications, bolt right on to that beloved MG and give you years of heavy-duty service.

My last alternator change was about 9 months ago. In all fairness I have driven my 1980 MGB over 11,000 miles in those nine months. It has almost become my daily driver. I do have an AM/FM stereo with a 10-disc changer in the boot. So, I guess my Lucas is a little over worked. But, even in the days when I drove the MG less than 5,000 miles a year, I found myself replacing the alternator about every 18 -24 months. I had already decided to upgrade on my next replacement.

I installed the upgrade due to a late night visit by the "Prince of Darkness" on a 3-day weekend trip to Atlanta, GA.

I called my friend Darryl Beech of Charleston Import Automotive in Charleston, SC to discuss the alternatives. Darryl is a Bosch Product and British Car Specialist. His recommendation for the upgrade is the alternator for a '91-'95 Saturn SW1 SL Series 1.9 Liter 116-L4 FII SOHC. He has done this upgrade in his shop many times and with his encouragement, I am passing this on to you.

Part Numbers: Bosch -AL8657N or AL8657X, Delco -21020854 or 21022863, Lester (Scrap Yard) -8107 or 8115. The "First Build" of these alternators are 11 O-amp, the "Second Build" are 96-amp. (Important -This is a non "self-exciting" type alternator). Other than more than doubling your amperage, another benefit is these alternators are ."shelf items" for most auto parts stores. No more "we can have it here tomorrow". Bonus! The Saturn unit is shorter than the Lucas. Therefore, easier oil filter changes.

Mine came from Advance Auto Parts, Part #PB1073. It sells for $66.99 {at the time of Daryll's publishing} plus a onetime core charge of $30.00. That's a bargain even with the core charge. Add $2.00 for the replacement plug, Part # Caltrim 08627.

Advance alternators come with a lifetime warranty. My last Lucas came from Advance and the good folks there exchanged the Lucas for the Saturn and even refunded me a few dollars since the Lucas was $95 and the Saturn only $66.99. They understand customer service and I highly recommend Advance Auto Parts.

The Saturn unit is modified and installed as follows:

Parts required -

Saturn Alternator, 3-Wire GM Type Replacement Plug (also readily available) and a V Belt pulley with a 3 1/4" hole (available at your local auto electrical shop), your Lucas pulley cannot be used because the shaft is much smaller in diameter than the Saturn. I recommend that you take the Saturn Alternator to your auto electircal shop and have the V-Belt pulley fitted. (update: Although this was not the case on my 1980 Roadster. I have been told by a few folks that have made this
conversion, a longer belt was needed, possibly due to repositioning of the alternator or pulley size variations) and in some cases, a fraction of an inch needed to be ground off of the adjustment link (brace/bracket) as it may, in some cases, be a bit long on the alternator side for the Bosch unit.

Tools Required -

1/2" wrench, 5/8' wrench, wire cutters, knife or wire stripper and a set of reverse impact sockets (for removing housing bolts on Saturn Alternator)

BEFORE BEGINNING INSTALLATION. DISCONNECT BATTERY CABLES!!!

Saturn Alternator and Replacement Plug

Note that the mounting holes on the Saturn unit are approximately 90 degrees opposed to those on the Lucas. You must remove the serpentine pulley, cooling fins and the 3 housing bolts. Rotate the front housing approximately 90 degrees clockwise. When rotating the front housing, take care to lift the front housing only enough to rotate it. This will insure that no internal damage occurs.
After rotation, replace the 3 housing bolts and tighten. The replacement plug is also shown in this photo.

{As you can see in this photo, the mounting "ear" on the front of the unaltered Saturn alternator that you will use for this conversion is, as said above, 90 degrees counter clockwise from where you will want it to be when installing.  Follow Daryll's instructions, and CAREFULLY lift the front cover JUST ENOUGH to be able to move it clockwise into the correct position.  If you move it apart too far, you risk having to dismantle the unit to correct the situation!!!!! ~ Bob M.}

Saturn alternator with front housing rotated 90 degrees clockwise and Lucas OEM type alternator
Replace cooling fins and install v-belt pulley to Saturn Alternator
KEEP THE SERPENTINE PULLEY TO REINSTALL IN THE EVENT YOU NEED TO RETURN THE SATURN ALTERNATOR

Remove Lucas plug from wiring harness and attach the replacement plug as shown below.

REPLACEMENT PLUG -Attach Brown wife to Ignition lead from harness (Brown wire with Yellow stripe). The large Red wire
attaches to the battery post on rear of the Saturn alternator (See below). The Black wire is not used.


UPDATE: In the event a 3 wire replacement plug is not available, the 4 wire can be used. Attach the large Red wire to the BATT terminal at the rear of the alternator, attach the Green wire to the Ignition lead (Brown/Yellow). The other two wires are not used.


Attach Brown Starter Lead(s) (Hot) from wiring harness and Red wire from Replacement Plug to battery Post. Depending on the year model of your MG, there may be one or two leads from the starter.

Attach plug and install Saturn alternator to engine. Adjust belt tension to NMT 112" Belt Deflection between pulleys.
Reconnect Battery Cables. Go for a long drive, you deserve it!


Safety Fast!
Darryl McLendon





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To print this page, you may need to set Printing for Landscape orientation or Scale to Fit your printer's paper.












  

Wire Color Codes
N - Brown  -  Battery connections  (at solenoid)    NY - Brown/Yellow - dash  warning light    W - White  -  Switched power from ignition switch

Many thanks to Daniel Wong for the use of his photo graphic, below ©.



NOTE - I recommend using two  # 10 ga. wires to route alternator output to the battery - Use the existing large OE Brown wire and then add a second 10 ga. wire from the second spade connector to the battery connection at the solenoid. I used the very flexible rope-lay type power cable used frequently for providing 12VDC power to high current car stereo power amplifiers. You should be able to find this wire sold even at Wal-Mart, Circuit City, or Radio Shack. Use a 3/8" female connector (available at NAPA {Belden #784349} or other auto parts stores) for connecting to the alternator output male spade terminals. YOU MAY NOT WISH TO ADD THE SECOND #10 ga. WIRE, BUT IT WILL SIMPLY ALLOW A SECOND LARGE CAPACITY ROUTE FOR POWER FROM THE ALTERNATOR TO REACH THE BATTERY AND ALL THE OTHER LOADS IN YOUR ELECTRICAL SYSTEM AND WILL DO NO HARM. Adding the second wire may not do much for you most of the time, but when you do find yourself using all your high current draw equipment at the same time, it will allow your system to deliver max. energy a bit more easily, and provide a safer load distribution for your wiring for your higher output alternator.  And, it cannot hurt when charging a marginal battery. 

Do consider adding a fusible link to both of the 10 ga. output wires to protect both your wiring and the alternator.  Fusible links can be purchased from suppliers such as NAPA or the various chains.  Perhaps the most common units are those used by GM cars. These are mounted in a moulded rubber jacket, flagged to show their presence, and where they are.  They have a wire pigtail coming out of each end of the vinyl or rubber moulding. The ones I used are mounted inline with the alternator outputs and can be attached to the heavier cables and their opposite ends to the larger female spade connectors which fit into the plastic alternator connector, if you choose to use one.  Fuses and fusible links are a good thing, and you will do yourself and your wiring a favor by updating your wiring with them!!

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The only connections to the Bosch {Lucas 18ACR} unit that need to be made are those which you will find in the larger plug cavity!

You can carefully pull the existing connectors out of the connecting plug(s) of your early B by inserting a very small thin tool (I have used a fine jeweler's screw driver) into the plastic connector(s) and compressing the "ears" or barbs that hold them in place and pulling the connectors out.


The two large (3/8") male blade connectors (B+) in the plug well lead to the battery wire connection on your starter solenoid. Use the existing large MGB brown wire and a second # 10ga. wire which you should route along the same basic path.  Use only automotive or marine high strand count power wire as discussed above. It will allow you to route it much more easily and do a better job of carrying more current. You will need to buy a larger 3/8" female spade lug connector to connect the new wire to the alternator output (B+) spade lug. The small (1/4") male blade connector (D+) in the well goes to the small brown/yellow wire for the indicator light on the dash. The small female connector in the MGB plug with two brown/yellow wires is from the dash. Strip the tape on the harness back to see which is the main small brown/yellow wire and which is just the loop. Use the main wire. If you cannot figure out which is which, do a continuity check with a Volt-ohmmeter between each brown/yellow wire at the alternator and the brown/yellow wire that attaches to the dash charge lamp. The correct lead will show continuity.

The threaded post  terminal sticking out of the back of the Bosch unit is a take-off for a tachometer for some original equipment Bosch applications and IS NOT used here. Leave this terminal alone and insulate it with heat shrink tubing, electrical tape, or a cap plug cover. This does not effect alternator operation in any way.

The other terminal (+) found in a small well on the body of the alternator is the connection for battery sensing. On the new regulators provided by Bosch and other aftermarketers, this terminal is made part of the main (large blade terminals) on the Bosch unit and makes the unit "self-sensing" . You can then insulate the factory Original Equipment small Brown sensing wire's bare female connector with heat shrink tubing and push this onto the Bosch "+" or "Bat" terminal with no issues...... or..... you can tie this same wire back onto the harness and tape it off after removing the other end of it from the starter, just in case you ever want to revert back to the original system.                 


Good luck!


{For those who may need it, a schematic diagram of this Bosch Alternator's internal circuits is given below.}



Questions? Comments? Good/Bad Experiences?  Feedback is good, it helps to make things better for everyone using this site.  Please use the Feedback form on the home page or send your email comments to:  bobmunch64@yahoo.com
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Notice:

The author of this site makes no representations or warranties about the information provided through this web site, including any hypertext links or any other items used either directly or indirectly from the web site and reserves the right to make changes and corrections at any time, without notice.  The author accepts no liability for any inaccuracies or omissions in this web site and any decisions based on information contained in this website are the sole responsibility of the visitor.  The author accepts no liability for any direct, special, indirect, or consequential damages or injuries or any other damages or injuries of whatsoever kind resulting from whatever cause through the use of any information obtained either directly or indirectly from this web site.       

Bosch Alternator Conversion for the MGB text and photos © Bob Muenchausen, 1999, 2005
Wiring Graphic © Daniel Wong.  The Saturn Alternator information presented is archived material originally authored and presented by Daryll McLendon on his previously existing website, One Fast MGB! and is presented here for informational purposes only since it no longer exists on the internet as his own website.


 
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