'87 Mustang (speed density) harness
'88-'93 Mustang SEFI harness
'95 Mustang (MAF) harness

Wiring Modifications By Circuit...

In the text below, the connector ID numbers are listed first are for '86-'87 harnesses. The 2nd ID numbers listed in brackets ( ) is the connector ID number for the '88-'91 harnesses. EXAMPLE- X-04(FE-02)...X-04 is the connector ID number for the '86-'87 harnesses, (FE-02) is the connector ID number for the '88-'91 harnesses.

Re-connecting The Battery To The RX-7's Harness...when the rotaryís engine harness is removed from the car, a vital wire is lost that runs from the 80A fuse in the main fuse box to the large stud on the back of the RX-7ís alternator, and also to the ignition switch through connector X-23 (a large single terminal connector located between the main fuse block and the driverís strut tower). This wire was originally black, and very thick, appx. 10ga. Be sure to replace it with wire of at least the same capacity, that connects all three points in the circuit.

Starter Wiring...The wiring for the Ford starter is almost identical to that of the RX-7. The only real difference is that Ford uses a starter relay, which has a "S" terminal on the solenoid. The Mazda harness has a female "spade" type connector, the Ford uses a small stud style push-on connection. The problem is that this wire was part of the engine harness, which was removed with the rotary engine. You can access this black w/ white stripe wire at connector X-08(FE-05) (listed in the harness ID section).
...Manual trans T-5 and T-56 applications...Route a wire from X-08's black w/ white stripe wire that extends to the Ford solenoid's "S" terminal.
...C4 / AOD automatic trans applications...Route a wire from connector X-08(FE-05) black w/ white stripe wire that extends thru the neutral safety switch, then to the Ford solenoid's "S" terminal. Be sure that the neutral safety switch interrupts this wire in all shifter positions except neutral and park. If it does not, adjust the switch until it does.

Alternator Wiring...Mazda routed the alternator wires differently depending on model...
...Non turbo models...If you are using the RX-7 alternator, the small "T" shaped connector A-12(EM-36) that plugs into the alternator does not need to be changed, but these wires were routed thru the emissions harness (located on the passenger side) and will need to be seperated from it and salvaged if the emissions harness is removed.
...Turbo-II models...The alternator wiring for the Turbo-II models was routed within the engine harness, which was removed with the rotary engine. You can access these wires at the Turbo harness's connector X-05 (listed above in the harness ID section), where they should be extended to your Mazda alternator's new location. You can recover the needed "T" shaped alternator connector A-02(E-02) (listed in ID section) from the rotary engine's discarded engine harness.

Ignition Wiring...Power for your Ford engine's ignition system should come from the connector Ba-08(F-34) that went to the rotary engine's "Trailing Coil w/ Igniter", that was located on the inner fender panel behind the driver's side strut tower. Power for this black w/ yellow stripe wire come from a 40amp fusible link, and is turned "on" by the "Main Relay" when the ignition switch is in either the "start" or "run" positions.

Locating & Re-wiring The RX-7's Fuel Pump Control Relay(s)...Mazda calls the main fuel pump relay the "Circuit Opening Relay", a square relay with a 6 terminal connector Ba-01(F-08) (2 rows of 3), which is located under the steering column. For the non-turbo models, this is the only fuel pump control relay. The Turbo II models used an additional relay called the "Fuel Pump Relay & Resistor", located in front of the passenger side strut tower under the stock air cleaner, using a round connector (F-09) with 6 terminals (2 rows of 3). The wiring for each is as follows...
...Non-Turbo and Turbo Models-...on both non-turbo and turbo models, the ignition switch sends power to one of 2 coils in the circuit opening relay. The "run" coil gets it's power from the ignition switch in the "run" position (black w/ white stripe wire in Ba-01(F-08)). The ground leg of this coil (brown wire in Ba-01(F-08)) goes out to the airflow meter, where it is grounded when the airflow meter senses actual flow. If the ignition is on, simply grounding this wire will close the relay contacts and power up the fuel pump. When you install a V-8, you remove the rotary engine's airflow meter, which dis-ables the fuel pump with the ignition switch in the "run" position. The airflow meter performed an important safety function, which was to shut off the fuel pump if the ignition switch was on but the engine was stopped. This situation could occur during an accident in which the engine stops but the driver is unable or does not think to shut off the ignition, so the fuel pump keeps pumping fuel, possibly creating a dangerous situation. Simply grounding this brown wire would dis-able this safety feature. A solution is to use either an oil pressure switch or an "inertia switch" such as that used by most all fuel injected Ford passenger cars. These switches are available inexpensively in most any wrecking yard, and are typically located on the passenger side behind the rear wheels. They are typically located behind a removable panel, and have a "reset" button.
...Turbo II-...On the turbo models, there is also the "fuel pump relay and resistor". It's function was to provide extra fuel pressure under boost conditions by closing an internal set of contacts to effectively bypass a voltage dropping resistor. When installing a V-8, you can boost fuel pump voltage to get more fuel volume by grounding the green w/ red stripe wire at the X-16(FEM-02) connector, now an open connector located in the passenger kick panel area, formerly connected to the emissions harness (no longer needed and probably removed by now). X-16(FEM-02) can be identified as a flat rectangular connector w/ 13 terminals, arranged in 2 rows. If you install nitrous, you might want to rig this wire to boost fuel pressure when the spray comes on.

Temp Sender Location & Installation...The RX-7's rotary engine's temperature sending unit for the dash gauge is a very small single terminal device located below the rotary engine's oil filter. It can be removed from the rotary and installed in your V-8 using a special reducing bushing. After installation, the sending unit should be connected to the yellow w/ black stripe wire in connector X-16 (non-turbo) or X-15 (turbo). The original connector for the sending unit, C-04(EM-33), can be salvaged from the discarded emissions harness and re-used here for a factory quality connection.

Oil Pressure Sending Unit Wiring... The rotary engine's oil pressure sending unit for the dash gauge is located large round single terminal device located below the rotary engine's oil filter. It can be removed from the rotary and installed in your V-8's engine block using a 1/8" pipe thread 45 degree elebow fitting (male threads for the block, female threads for the sender). A single wrap of the threads with teflon tape should ensure leak free operation. After installation, the sending unit should be connected to the yellow w/ red stripe wire in connector X-04(FE-02). The original connector for the sending unit, C-05(E-10), can be salvaged from the discarded emissions harness and re-used here for a factory quality connection.

Tachometer Signal Wiring...The RX-7's tachometer originally got it's signal from the ignition system's trailing coil/igniter, originally located on the inner fender panel behind the driver's side strut tower. The tach was connected to the igniter with a yellow w/ blue stripe wire at connector Ba-07(F-35), a square 4 terminal connector (2 rows of 2). This yellow w/ blue stripe wire needs to be connected to the V-8's tach signal source, typically either the "-" side of the ignition coil or the "tach" terminal of the electronic ignition box.

Back-up Lite Switch...To operate the RX-7's back-up lites, Mazda used a transmission mounted SPST switch to complete the circuit. When the RX-7's engine harness is removed with the rotary engine, part of this circuit is removed as well. To restore this circuit, a harness extension will need to be added at connector X-04(FE-02), a rectangular 6 pole connector (2 rows of 3) located under the hood on the driver's side of the brake master cylinder. 2 of the wires in this connector are for the back-up lite switch. These wires wires are...
...black wire w/ yellow stripe- comes from 7.5a fuse in underdash fusebox.
...red wire w/ green stripe- goes to back-up lites.
Connecting these two wires together w/ a jumper wire will turn on the RX-7's back-up lites when the ignition switch is in the "ignition" and "start" positions. Routing and connecting these two wires to your new transmission's back-up lite switch will enable the RX-7 back-up lites when "reverse" position of the shifter is selected.

Low Coolant Level Warning Buzzer and Lite...the original sensor for this circuit was located in the RX-7's top radiator tank. If you do not want to go to the trouble to keep this part of the warning system intact, you can either dis-able the buzzer (located on the outside/bottom of the dash pod), or, simply locate the brown wire that formerly went to the coolant level sensor and connect it to ground. If you need help locating this wire, it is part of the front harness, a single wire leg that comes out of the front harness just in back of the passenger side headlite.

Low Oil Level Sensor Wiring Modifications...If you have an LT-1, you may already have a low oil level sensor installed in your oil pan. Problem is, the RX-7 sensor and the LT-1 sensor work exactly opposite of each other. With the RX-7 sensor, low oil level closes a reed switch, grounding one leg of the warning lite bulb, causing it to illuminate. With the Chevy sensor, low oil level causes the ground leg to be opened. If you want to retaining this function you will need to use a relay to make the sensor compatible with the warning lite circuit.

AC System- Relay, Compressor & Pressure Switch...Only 2 circuits need modification for your AC system to function properly.
...AC main relay (G-08)... in the #2 position in the relay rack located in the nose of the car just ahead of the hood latch. It has a square connector with 4 wires attached. It's terminals need to be re-connected as follows...
......blue w/ white stripe wire...connect this wire to one leg of the RX-7's pressure switch located near the RX-7's reciever/drier. The other leg of the pressure switch connects to "12v +" thru the "AC ON" switch.
......red w/ yellow stripe wire...connect this wire to ground.
......black w/ white stripe wire...connect this wire to the "+" side of your compressor's magnetic clutch. Connect the other leg of the magnetic clutch coil goes to ground.
......blue w/ black stripe wire...connect this wire to a "12v ign on" power source.
...AC pressure switch...a 2 terminal switch located next to the RX-7's reciever/drier. The switch's harness connector can be clipped from the front harness and re-used. The 2 legs of this switch/connector can re-wired as follows...
......blue wire...DO NOT CHANGE- oem wire connects to "12v +" thru the "AC ON" switch.
......blue w/ orange stripe wire...connect to the AC Relay's blue w/ black stripe terminal.

'87 Mustang (speed density) harness
'88-'93 Mustang SEFI harness
'95 Mustang (MAF) harness


Rotary Specific Electrical Items That Can Be Removed

The items listed in this section are specific to the rotary engine and can be safely removed without compromising the function of other systems. They are listed below along with their location, connector and wire detail, and a description of where the other end of the deletable wires go.

Sub-zero motor...connector Ba-02, a 2 conductor "T" shaped connector located on the passenger side firewall area below the wiper motor. This connector is part of the emissions harness which can be partially removed. The wires are...
...black w/ red stripe...the other end of this wire goes to connector X-15 in the passenger side kick panel area.
...black w/ red stripe...the other end of this wire goes to connector X-15 in the passenger side kick panel area.

Auto Trans Control Unit...(auto only) connector A-09, a rectangular 11 conductor connector (1 row of 5, 1 row of 6) with only 8 wires, located in the passenger kick panel area. The wires are...
...orange w/ white stripe...
...green w/ red stripe...
...orange...
...black w/ red stripe...the other end of this wire goes to connector A-10.
...brown...
...black w/ blue stripe...
...black w/ yellow stripe...the other end of this wire comes from a 7.5a fuse at X-07.
...black...the other end of this wire goes to the harness ground at (6).

Lock-up Relay...(automatic only) connector A-14, a rectangular 6 conductor connector (2 rows of 3) located on the relay rack in front of the RX-7's hood latch. There are 4 wires here...
...black w/ white stripe...these 2 wires are connected together in the front harness, and come from a 15a fuse in X-07.
...black w/ white stripe...same as above.
...red w/ blue stripe...the other end of this wire goes to connector X-08.
...red w/ yellow stripe...the other end of this wire went to connector A-15 at the vacuum switch located in front of the passenger side strut tower.

4AT Relay...(automatic only) connector A-10, a rectangular 4 conductor connector (2 rows of 2) located on the relay rack in front of the RX-7's hood latch. There are 4 wires here...
...yellow...the other end of this wire went to connector A-08.
...black w/ yellow stripe...the other end of this wire went to a 7.5a fuse in X-07.
...black w/ white stripe...the other end of this wire went to connector X-05.
...black w/ red stripe...the other end of this wire went to connector A-09 on the automatic transmission control unit.

Vac Switch...connector A-15, a 2 conductor "T" shaped connector located in front of the passenger side strut tower.
...red w/ yellow stripe...this wire is top of the "T" in A-15. The other end of this wire goes to connector A-14.
...black w/ blue stripe...this wire is the leg of the "T" in A-15. The other end of this wire goes to connector X-04 and to Ba-28 on the rotary engine's ECU

Leading Coil w/ Igniter...connector Ba-09, a flat 2 conductor connector (1 row of 2) located in front of the driver's strut tower.
...black w/ yellow stripe...this wire connects with other black w/ yellow stripe wires in the front harness, but they all come from Ba-06 at the main relay. This wire is a good source of switched 12v power for your V-8's ignition system.
...green w/ yellow stripe...the other end of this wire is terminal "V" on connector Ba-28 at the rotary engine's ECU.

Trailing Coil w/ Igniter...2 connectors, Ba-07 & Ba-08.
...Ba-07...is a square 4 conductor connector (2 rows of 2) located in back of the driver's strut tower.
......blue w/ yellow stripe...the other end of this wire is terminal "X" in connector Ba-28 at the rotary engine's ECU.
......brown w/ yellow stripe...the other end of this wire is terminal "U" in connector Ba-28 at the rotary engine's ECU.
......blue w/ red stripe...the other end of this wire is terminal "M" in connector Ba-28 at the rotary engine's ECU.
......yellow w/ blue stripe...the other end of this wire goes to the RX-7's tach and also to the "check connector" Ba-11, a single conductor bullet style connector located between the driver's side strut tower and the firewall.
...Ba-08...is a flat 2 conductor connector (1 row of 2) located in back of the driver's side strut tower. There are 2 wires of the same color here...
......black w/ yellow stripe...this wire connects with other black w/ yellow stripe wires in the front harness, but they all come from Ba-06 at the main relay. This wire is a good source of switched 12v power for your V-8's ignition system.
......black w/ yellow stripe...this wire connects with other black w/ yellow stripe wires in the front harness, but they all come from Ba-06 at the main relay. This wire is a good source of switched 12v power for your V-8's ignition system.

Water Temp Switch...2 single conductor bullet style connectors, both labeled connector Ba-13, located in the bottom driver's side of the RX-7's stock radiator. The wires are...
...brown...the other end of this wire is terminal "H" in connector Ba-28 at the rotary engine's ECU.
...black...the other end of this wire goes to harness ground "5".

Injector Resistors...connector Ba-21, located in front of the passenger side strut tower. These are part of the emissions harness that can be partially removed. The wires are...
...black w/ yellow stripe...the other end of this wire goes to 2 wires at connector X-16.
...brown w/ yellow stripe...the other end of this wire goes to a rotary engine injector.
...brown w/ red stripe...the other end of this wire goes to a rotary engine injector.
...brown w/ white stripe...the other end of this wire goes to a rotary engine injector.
...brown...the other end of this wire goes to a rotary engine injector.

Rotary Engine ECU...there are 3 different connectors along the lower edge of the rotary engine's ECU. They are labeled differently on the non-turbo and turbo models. The 3 connectors here are...
...non-turbo...
......Ba-27...remove w/ emissions harness (plugged into lower driver's side of the rotary ECU).
......Bb-20...remove w/ emissions harness (plugged into lower center of the rotary ECU).
......Ba-28...a rectangular 24 conductor connector (2 rows of 12) that plugged into the far right lower side of the rotary engine's ECU.
...turbo II...
......Ba-15...remove w/ emissions harness (plugged into lower driver's side of the rotary ECU).
......Bb-25...remove w/ emissions harness (plugged into lower center of the rotary ECU).
......Ba-26...a rectangular 24 conductor connector (2 rows of 12) that plugged into the far right lower side of the rotary engine's ECU.

Variable Resistor...connector Bb-12, round 3 conductor plug, located in front of the passenger side strut tower. This connector is part of the emissions harness that can be partially removed. The wires are...
...brown w/ white stripe...
...brown w/ black stripe...
...green w/ black stripe...

Pressure Sensor...(non-turbo only) connector Bb-17, a rectangular 4 conductor connector (2 rows of 2) located just in front of the passenger side strut tower. This connector is part of the emissions harness that can be partially removed. The wires are...
...black w/ white stripe...
...brown w/ black stripe...
...brown w/ red stripe...
...brown w/ white stripe...

Boost Pressure Sensor...(Turbo II only) connector Bb-16, a rectangular 4 conductor connector (2 rows of 2) located just in front of the passenger side strut tower. This connector is part of the emissions harness that can be partially removed. The wires are...
...black w/ white stripe...
...brown w/ black stripe...
...brown w/ red stripe...
...brown w/ white stripe...

Air Bypass Relay...(non-turbo only) connector Bb-05, a rectangular 4 conductor connector (2 rows of 2) located just in front of the passenger side strut tower. This connector is part of the front harness which will remain in the car. The wires that can be deleted are...
...black...the other end of this wire goes to the harness ground at (5).
...black w/ white stripe...this wire connects to a few points in the front harness, 2 wires in X-16, "check connector" Ba-16, and the main relay at Ba-06.
...brown w/ yellow stripe...the other end of this wire goes to connector X-16.
...red w/ yellow stripe...the other end of this wire goes to terminal "C" of connector Ba-28 at the rotary engine's ECU.

Air Flow Meter...connector Bb-16, a flat 7 conductor connector (1 row of 7) located under the rotary engine's air cleaner. This connector is part of the emissions harness that can be partially removed. The wires are...
...green w/ orange stripe...
...green w/ blue stripe...
...brown w/ black stripe...connects to the other brown w/ black stripe wire in the emissions harness.
...brown w/ white stripe...
...brown w/ black stripe...connects to the other brown w/ black stripe wire in the emissions harness.
...black...
...brown...

Atmospheric Pressure Sensor...connector Bb-13, a rectangular 4 conductor connector (2 rows of 2) located in the passenger side kick panel area. This connector is part of the emissions harness that can be partially removed. The wires are...
...brown w/ black stripe...
...black w/ white stripe...
...green w/ yellow stripe...
...brown w/ white stripe...

Fan Relay...connector Bc-02, a rectangular 6 conductor connector (2 rows of 3) located in the front relay rack ahead of the RX-7's hood latch. The fan relay is the round relay mounted on the passenger side. Only 4 wires are used. The wires are...
...black...the other end of this wire is in connector Bc-05 at the cooling fan control unit, which is located in the passenger side kick panel area.
...black w/ yellow stripe...the other end of this wire connects to 2 places. It comes from a 7.5a fuse in X-07, and also goes to Bc-05 at the cooling fan control unit.
...yellow w/ black stripe...the other end of this wire goes to the ground side of the cooling fan motor.
...green w/ red stripe...the other end of this wire goes to connector Bc-05 at the cooling fan control unit. It also connects to connector Bc-08, which is connected to the cooling fan sub-relay.

Fan Sub-Relay...(w/ AC only) connector Bc-04, a rectangular 4 conductor connector (2 rows of 2) located in the front relay rack ahead of the RX-7's hood latch. The fan sub-relay is the round relay mounted on the driver's side. The wires are...
...yellow...the other end of this wire comes from a 15a fuse in X-07.
...green w/ blue stripe...the other end of this wire goes to connector Bc-08 up by the relay rack in front of the hood latch, which then connects to connector X-15 (non-turbo) or X-16 (turbo II).
...green w/ red stripe...the other end of this wire goes to connector Bc-05 at the cooling fan control unit.
...blue w/ orange stripe...the other end of this wire goes to connector Bc-09, a diode located next to the relay rack in front of the hood latch.


MAZDA RX-7 Tachometer Re-calibration

Re-calibrating the stock RX-7 tach for V-6 or V-8 use is a fairly straight forward process that involves dis-assembly of the dash, and removal of the tach assembly. The 1st step is to remove the whole dash pod from the car. There are 2 harness connectors to dis-connect from the rear, as well as the speedometer cable (a retention tang must be compressed to dis-connect the cable). After the pod is out, the dash face can be removed, usually attached with 4 phillip's head screws. Then the tach itself can be removed from the front of the main dash circuit board by removing the screws or nuts on the back side that connect it to the circuit board (depending on the model). Try not to leave any fingerprints on the satin black inner part of the dash face, as they are quite hard to remove.

After the tach is removed from the dash, it must be wired up to a signal source, usually done by using 4 long jumper wires w/ alligator clips.

RX-7 tach layout
With the 2nd gen tach removed and viewed from the rear, the connections to the dash circuit board can be seen, which look like flat brass formed strips. I label the connections as follows ;

The upper extreme left connection, which looks like a simple round eye for attaching a screw, is for the over-rev buzzer, and not connected to anything during the re-cal process.

The upper right connection, which also looks like a simple eye, is the ground terminal.

The lower left connection, which looks like a flat formed strip with a notch cut in it just below and to the right of the screw hole, is the "+" connection, which is connected to 12v.

The lower extreme right connection, which also looks like a flat strip except with a notch just below and to the left of the screw hole, is the "signal" connection that typically hooks to the coil "-" on a standard ign, or the "tach" terminal of a GM HEI distributor.

The re-cal process
PREFERRED SIGNAL SOURCE... an inexpensive 12v battery charger can be used as a deadly accurate signal source for the re-cal of your tach. This signal source is so steady and accurate that there is no need to compare the reading with another V-8 calibrated tach. Battery chargers typically use a rectifier bridge to convert the AC power source into DC. This turns the 60 hertz sine wave input into a 120 hertz ripple wave DC output. The ripple wave output is read as 3600rpm by the stock rotary calibrated RX-7 tach. For a V-6 application, an RX-7 tach should be adjusted to read this signal as 2400rpm. For a V-8 application, adjust your RX-7 tach to read this ripple signal as 1800rpm. Please note that you must use a 12v battery for a power source, and the battery charger as a signal source only. The ground wires for both the battery and the battery charger should be connected to the ground terminal of the tach.
NOTE: Be sure that the RX-7 tach is about the same orientation as when installed, because the re-calibration may be off if done with the face in a horizontal plane.

Use the test leads to hook-up your RX-7 tach to the signal source and power source as described above.

With your signal source plugged in and your un-modified tach wired as above, it should be putting out a reading of about 3600rpms. To correct your RX-7 tach's reading, the cal-pot must be adjusted. It is a round white adjustable potentiometer located on the end of the circuit board near R3. The adjustment is secured from the factory with a locking compound, so your initial turn of the adjuster will be difficult until the locking compound's seal is broken. Be patient, and don't break anything.

When you get the adjustment free'd up you will be able to observe the effects of adjustment on the RX-7 tach's needle. Try to adjust until the tach reads correctly for your application (2400rpm for V-6, 1800rpm for V-8). If you don't have enough adjustment to get the correct reading, the value of the cal-pot must be altered.

The method we use is to add a 1500 ohm resistor in parallel with the resistor BEFORE the cal-pot (usually marked R3). I usually add this resistor to the backside of the board (where the solder joints are made) to make things easier. The 1500 ohm resistor will get the calibration close enough that minor adjustment of the cal-pot is all that is needed.

After adding the resistor, repeat the process. Now, the cal-pot should have plenty of range.

If you have any problems with the above process, feel free to contact us, or you can send your tach to us for the modification (we usually have re-cal'd tachs in stock and ready to ship on an exchange basis). We charge $55.00, which includes return shipping (inside the US.) Just mail your tach and a check for $55. to:

Granny's Speed Shop
POB 814
Concrete, WA 98237


Next page....

1....Introduction....

2....Considerations & Requirements....

3....Getting Started....

4....Engine / Transmission Installation....

5....Exhaust / Throttle Cable / Accessory Drive / Pulleys....

6....Cooling / Fuel Systems....

7....RX-7 Wiring Harness Connector ID and Circuit Locations....

8....Electrical System Modifications By Circuit....

9....Start-up / Troubleshooting....

10....Upgrades....

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