IRCM Relay Box $?

This may help......it's from NATO. I hope Joe doesn't mind!




Troubleshoot & Repair Your Malfunctioning
Integrated Relay Control Module (IRCM)



Please note that this article was developed using an IRCM from an 87/88 Turbocoupe. IRCM's from other years may or may not have any resemblance to the one used for the article.

The primary function of the IRCM in our Turbo Coupes is to provide a controlled source of power (switched 12 volts) to the engine control computer (ECC) and it's related components. Additionally, it has several secondary functions; it houses and controls the fuel pump relay and the engine cooling fan relay(s), and also controls the air conditioning clutch by means of a solid-state transistorized switching circuit.


EEC power relay
When 12 volts from the ignition switch is applied to the IRCM, the EEC relay is energized and supplies power for the internal IRCM circuitry and the EEC itself. Note that this power source is switched via the ignition, and is not constantly present.

Fuel pump relay
Once the EEC power relay applies power to the EEC, a signal is sent by the EEC to the IRCM that energizes the fuel pump relay, which in turn supplies power to the fuel pump. Note that this circuit has other protective devices, e.g. the inertia switch in the trunk that shuts off power to the the fuel pump in case of a collision.

Cooling fan relay(s)
As measured by the ECT sensor, when the coolant temperature reaches 210° the EEC signals the IRCM to turn on the primary (passenger side) radiator cooling fan. Once the temperature drops below about 190°, the fan is shut off. If the temperature exceeds about 220° , the EEC also tells the IRCM to turn on the secondary (drivers side) cooling fan. The shut-off temperature for this fan is around 200°. Additionally, when the air conditioning compressor is turned on, the EEC will cause the IRCM to energize the primary fan. Finally, if the A/C high-side pressure exceeds about 310psi, the secondary fan will be energized.

Air conditioning clutch control
The air conditioning compressor clutch is powered through a solid-state transistor circuit in the IRCM. Basically if the A/C is active, the circuit is told to energize the clutch. This changes somewhat in the case of a vehicle with electronic climate control. Additionally this circuit is controlled by the A/C low pressure switch which disallows the A/C clutch being energized if the refrigerant pressure is too low.



--------------------------------------------------------------------------------IRCM Disassembly & Reassembly


View attachment 473866

View attachment 473867

Disassembly
1. Carefully drill off the heads of the two swaged "rivets" that hold the top of the IRCM onto the bottom. A 1/4" drill bit is the perfect size. Also the use of a drill press is highly recommended to insure precise control. You do not want to drill too deep and wind up with the drill bit in the PC board! See picture on left; note only one rivet shown, there are two to remove.
2. Now remove the case top from the bottom/pc board assembly.
3. Using the same technique as in step (1), carefully remove the two "rivet" heads that hold the PC board onto the metal bottom section of the IRCM. Again use care and precision. Refer to picture on right.
4. Next remove the Torx machine screw that holds the aluminum heat sink at "Q3" to the base-plate metal tab. Then carefully remove the PC board from the metal base of the IRCM. Suggestion: put the Torx screw back into the tapped aluminum heat sink hole it was removed from to avoid misplacing it.
Reassembly
1. Remove the Torx screw from the aluminum heatsink and properly position the PC board onto the metal IRCM bottom plate. Replace the Torx screw in the correct location but leave it loose for now.
2. Use two small machine screws, two non-conductive washers (fiber, phenolic, or plastic), and two nuts to secure the PC board back onto the metal base plate of the IRCM. 4/40 X 3/8" machine screws are close to perfect (alternatively nylon screws and nuts could be used). Snug the nuts onto the screws. Now snug down the Torx screw that was installed in step reassembly step (1).
3. Replace the metal cover onto the PC board/base assembly and secure it with two machine screws, washers, and nuts. Again 4/40 X 3/8" machne screws are perfect. Lock washers may be used if desired; I did.


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IRCM Schematic & Parts List



View attachment 473869

This is the schematic of the 87/88 TC IRCM, as traced from the printed circuit board. The circuit all makes sense so I believe that this is 100% correct. In addition to the Jpeg image above, the schematic has also been included as an Adobe PDF file, and may be downloaded by clicking on THIS link. The PDF has better resolution and will also print better.



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R1 2.211K, 1/4W precision resistor
R2 Zero ohm jumper
R3 130K, 1/4W precision resistor
R4 31.5K, 1/4W precision resistor
R5 1K, 1/4W resistor
R6 62 ohm, 5W resistor
R7 1.5K, 1/4W resistor
R8 -none-
R9 68.2K, 1/4W resistor
R10 1.5K, 1/4W resistor
R11 100K, 1/4W resistor
R12 4.7K, 1/4W resistor
R13 -none-
R14 4.7K, 1/4W resistor

C1 0.01uF, 50V chip capacitor*
C2 -none-
C3 1uF, 63 volt electrolytic capacitor
C4 47uF, 10 volt electrolytic capacitor
C5 0.01uF, 50V chip capacitor*
* The operation voltage has be estimated from the circuit it is used in. Higher voltage capacitors may be subsituted without problems,

D1 *
D2 *
D3 -none-
D4 *
D5 *
*Diode requirements have been estimated from the circuitry. 1N4003 should work in all cases without problems.

Q1 *
Q2 *
Q3 Have yet been unable to determine parameters
Q4 *
Q5 *
Q6 *
* 2N2222A or similar transistors should function well in all these locations. The transistors in the IRCM use a part number that is completely unfamiliar.

Relays are all SPST with 40 amp comtacts, 12 V coils. Bosch number on relay is 0 332 014 162.


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IRCM Theory of Operation



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EEC Power Relay and Switching Circuit
K1 switches power to the EEC and internal IRCM circuits. The input voltage to the relay is sourced by IRCM pin 8 (constant +12 volts). That voltage connects directly to the relay contact and the relay coil through isolation diode D1. Reverse voltage suppressor diode D6 is connected across K1's coil to eliminate any reverse voltage spikes at the collector of Q1.

Q1 is an NPN transistor used as a switch. The emitter is grounded and the collector drives the coil of K1. The base is held in the normal "off" state by resistor R3. R1 limits the Q1 base current to around 5mA. Diode D2 is in series with the switching voltage, preventing a low-level (ground) from being applied to the base of Q1 when the ignition is off. Finally, C1 appears to be an RFI (radio frequency interference) "short" across D2, preventing RFI from being rectified by D2 and inadvertently turning Q1 on.

When the ignition is off, the base of Q1 is held low by R3 and the collector is in it's high impedance (off) state. When the ignition is on, current flows through IRCM pin 13, D2, and R1 into the base of Q1. This current turns the transistor on, switching the collector to it's low impedance (on) state, thus applying ground to the low side of the K1 coil, closing it's contacts. Contact closure then sources +12 volts to the high sides of the other relay coils, to the internal circuitry of the IRCM, and to the EEC through IRCM pin 24.

Fuel Pump Power Relay
K2 switches power to the fuel pump. K2's contact voltage is sourced from IRCM pin 8, and it's coil voltage is sourced from the K1 contacts. K2 is switched on by applying a ground to IRCM pin 18. Pin 18 is driven by an EEC output.

Secondary Cooling Fan Power Relay
K3 switches power to the secondary cooling fan. K3's contact voltage is sourced from IRCM pins 3 and 4, and it's coil voltage is sourced from the K1 contacts. K3 is switched on by applying a ground to IRCM pin 17, sending power to the fan via IRCM pins 6 and 7.

Primary Cooling Fan Power Relay
K4 switches power to the primary cooling fan. K4's contact voltage is sourced from IRCM pins 3 and 4, and it's coil voltage is sourced from the K1 contacts. When energized, K4 applies power to the primary fan via IRCM pins 1 and 2. K4 is energized via a switching circuit consisting of Q2, Q5, Q6, and their associated components.

IRCM pin 14 is the control input for the primary fan. If pin 14 were open(high), R4 applies +12 volts through the R9 current limiting resistor to the base of Q2. The current flowing into the Q2 base turns it on, making the collector "low". The "low" applied to Q5's base turns Q5 off, making it's collector "high". The "high" thus applied to the base of Q6 turns Q6 on, pulling the Q6 collector low, energizing K4, thus turning on the fan.

R14 and R12 are pull up resistors which normally pull the bases of Q6 and Q5 high. R11 and R9 form a voltage divider that turns Q2 on and off. C4 is used as a time delay that slows the turn on and shut off of the primary fan. Diode D4 is a reverse-voltage protection diode.

IRCM pin 14 is controlled by an output of the EEC. When the engine is below 190*, the EEC applies a "low" to pin 14. The low turns off Q2, allowing Q5 to turn on, causing Q6 to turn off. Conversely, when the EEC determines a need for the cooling fan, it removes the low from pin 14 which allows Q2 to turn on, Q5 shuts off, and Q6 turns on energising K4 and applying voltage to the main fan via IRCM pins 1 and 2. This circuit apparently acts as a kind of "failsafe" for the fan; if the EEC wire to IRCM pin 14 breaks or if the EEC output "opens", the main fan will run continuously.

Air Conditioning Compressor Clutch Control
Power for the air conditioning clutch is switched by the circuit consisting of Q4, Q8, and their associated components. 12 volts is sourced through IRCM pin 21 and is switched by Q8. Q8's switched output is applied to the AC clutch via IRCM pin 23. IRCM pin 22 is the signal used to control the AC clutch state, and originates from various control points depending on the vehicle's configuration (electronic climate control versus manual climate control).

Operation of the circuit is as follows: R7 is a pull-up resistor that applies 12 volts to IRCM pin 22 whenever the IRCM is activated. 12 volts is also applied to the base of Q4 through current limiting resistor R10. The current flowing into Q4's base turns it on, effectively grounding the collector. R5 is a pullup resistor that applies 12 volts to the base of Q8, keeping it biased in the "off" condition; whenever the Q4 collector goes low, Q8's bas is also pulled low by resistor R6 turning Q8 on. Current then flows from the source (IRCM pin 21) into the emitter of Q8 and out of Q8's collector to IRCM pin 23 and on to the AC compressor clutch coil turning it on. Conversely, if the AC clutch control lead (IRCM pin 22) is pulled low (ground) Then Q4 is turned off, likewise turning Q8 off thus turning off the AC compressor clutch.



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IMPORTANT NOTE FROM THE AUTHOR

This document is supplied "as-is" and without any warranty for accuracy or correctness, either expressed or implied. While due care and diligence was used in it's writing, without the direct input of the designer the operation of the IRCM as described herein is "assumed" and "to the best of my knowledge". The author assumes no liability for any damages whatsoever that use of this information may cause. That being said, I'm personally using it, but YMMV!



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