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
units 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 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 (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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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
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