ALTERNATOR MODIFICATION SERIES
DELCO 21SI & 22SI SINGLE WIRE SELF-EXCITING
The following modification procedure allows for the use of Sure Power Battery Isolator with the single wire Delco 21SI &
22SI Alternators. *NEWER 22SI HAS BEEN INTRODUCED, IF PLUG RECEPTICLE HAS 4 PIN TERMINALS SEE BACK
Procedure 1: Following instruction #1 and perform steps 1 and 2
Procedure 2: Perform an ohmmeter test. Set the meter on a low ohm scale. Place one probe on the #1 terminal of the
regulator and the other probe on the #2 terminal of the regulator; allow the meter to stabilize. The reading should read
infinity or no continuity. If no continuity exists proceed with instruction #1, steps 3 through 5.
Procedure 3: If continuity exists between the terminals (i.e. 0 ohms to 100 ohms, perform the instruction #2, or contact
Sure Power Industries for additional options.
NOTE: When performing the tests and modification procedures, the batteries must be disconnected from the system per
manufacturer's recommendations
Modification Instructions #1
Do not remove the alternator from the vehicle unless
it is inaccessible.
1. Remove the black rubber cap exposing the #1
and #2 terminals of the regulator.
2. Located between the #1 terminal and #2
terminal is a metal web joining the terminals.
Cut this web, separating the electrical connection.
3. Connect a sense wire from the #2 terminal of
the regulator to the #1 terminal of the Battery Isolator.
4. Use a Delco 21SI or 22SI plug connector (as
appropriate) to adapt this single wire alternator for
remote sense.
5. Proceed with general Battery Isolator Installation Instructions (#188012 page 2, Group 1, or Technical Bulletin #2).
Modification Instructions #2
Do not remove the
alternator from the vehicle
unless it is inaccessible.
1. Remove the black cover.
2. Remove the alternator
rear housing and stator.
3. Pull the brushes up and
insert a brush retainer pin.
Remove any grease that
may be on the brushes.
4. Remove the jumper
strap between the voltage
regulator and the positive rectifier heatsink, and replace the nuts.
5. Reassemble the alternator. Ensure that you remove the brush retainer pin.
6. Connect the sense wire from the alternator terminal #2 to the #1 terminal of the Battery Isolator. (Use a Delco 21SI or
22SI plug connector for this connector as appropriate).
NOTE: This connector and the pins are available, pre-wired, from most automotive stores.
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ALTERNATOR MODIFICATION SERIES
DELCO 24SI & 22SI WITH 4 PIN PLUG CONNECTOR
1. If the alternator is of the later design, look at plug connector recepticle and note if
the alternator has a 4-pin terminal as shown in Figure A.
2. Look at the male plug connector and see if there is a wire inserted into the "S"
position.
3. If there is not a wire in the "S" position one will have to be installed. Use the Sure
Power Connector Kit #144CD to install external sense wire.
4. Either install the wire and terminal or replace the entire plug.
Figure A
5. If the "S" terminal is already being used, plug modification is not necessary but the
"E" terminal on the isolator still needs to be used. The "E" terminal on the isolator
is used to allow the alternator to turn on. (see diagram below)
6. Install Isolator by following steps 1-9 on page 2 of 180012 and wire up the "E"
of the Isolator terminal through 6 amp circuit breaker to an ignition run source.
No power in the accessory side of circuit.
REMOTE SENSE MUST GO TO
THE #1 TERMINAL OF BATTERY
ISOLATOR OR AT MAIN BATTERY.
CAN USE SURE POWER 144CD
PLUG KIT.
SURE POWER
ISOLATOR
6 AMP
CIRCUIT
BREAKER
LITHO IN USA
NEW WIRE TO
FUSE CENTER
IGNITION RUN
POSITION
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