RTP Technical Bulletin

Transcription

1 RTP Technical Bulletin Category: ELECTRICAL REGISTERED TECHNICIANS PROGRAM Volume 1 Bulletin 4 This bulletin accompanies the associated texts on electrical and refrigeration as part of the February/ March 1999 Bulletins. By interpreting the information contained in the associated Bulletins a g r e a t e r appreciation will be gained as to why Ford (as with the o t h e r manufacturers ) h a v e introduced advanced fan c o n t r o l systems, and how the various s y s t e m s operate. EF/EL FALCON FAN WIRING This information is being presented to assist you in fully understanding the principles of switching of the EF/EL Falcon fan circuits. The full wiring diagram schematics for the fans were included in the previous RTP (5). This test accompanies those diagrams which were distributed as a matter of urgency (re members requests). This text covers the principles of switching but does not include dual speed motors (ie 120/160W motors) of 3 and 4 brush design. These will be addressed separately and an understanding of dual speed motor principles is not essential for this circuitry. CAUTIONARY NOTES: All vehicle manufacturers are extremely reluctant to allow/ endorse modifications to their systems - and understandably so - on viewing some wiring circuit modifications being circulated Australia wide they take out of circuit the normal fan switching strategies which protect against engine overheat and which automatically engage the fans in adaptive strategies (limp home) mode. When modifying modern electronically controlled systems extreme caution must be exercised to guard against any loss of normal switching, damage to sensitive electronics and inadvertent setting of fault codes (through tripping of watch dog circuits). 1

2 EF/EL SWITCHING Basic Introduction To The Systems The EF and EL are different systems. EF Models use one single speed fan (right hand) and one dual speed fan (left hand) controlled by four relays located behind the left hand headlight (near air cleaner). EL models use two single speed fans controlled by three relays (same location). The photo opposite shows the relay bank of an EL - three relays controlling 2 single speed fans. EF models use 4 relays controlling 1 single speed and 1 dual speed fan. The operation of both systems is controlled by the PCM (Powertrain Control Module - formally Engine Control Module (ECM)) (ie the main computer), and is a part of the total electronic management system of the vehicle of which the air conditioner is only a part. NOTE: Late model systems may include fans switched by either the PCM or the BCM (Body Control Module) with serial data/bus communication central to the system operation. These systems/principles will be addressed in future Bulletins. 2

3 EF FAN OPERATION The PCM will switch the relays according to the logic map below, dependant upon: engine operating conditions (ie over temp) air conditioner on/off blower speed selected (high or low fan speeds). As a part of the self test facility incorporated into the vehicle electronic system, there are dedicated tests for checking the operation of the fans (in the modes shown on the table opposite). Refer to the engine management section of the relevant workshop manual for details of this testing. Note: Basic switching guidelines only are shown here. The total logic control for fan switching is also dependant on other inputs into the PCM for engine protection and adaptive strategies. MODE 1 (LOW) MODE 2 MODE 3 (HIGH) Fan Speed rpm M1 PART (1400 rpm) FULL (2300 rpm) FULL (2300 rpm) Fan Speed rpm M2 PART (1400 rpm) PART (1900 rpm) FULL (2300 rpm) PCM CONTROL LOGIC RELAY No. 1 N/O OFF/OPEN OFF/OPEN ON/ TO M2 RELAY No. 2 N/O ON/ TO M2 ON/ TO M2 ON/ TO M2 RELAY No. 3 C/O OFF/ ON/OPEN TO M1 ON/OPEN TO M1 RELAY No. 4 C/O ON/OPEN DIVERTS TO M1 OFF/ OFF/ The PCM controls fan speeds as a part of its total management program. One critical input is terminal 86 (L6) or 44 (V8). This input tells the PCM the blower motor speed and will only allow low speed of the condenser/radiator fans when lower blower fan speeds are selected (or below fan speed 5 on Electronic Climate Control Systems). NOTE: High fan speeds will still be engaged if the PCM receives a high engine coolant temperature signal (via an ECT sensor input into the PCM) even if low blower fan speeds are selected. (As part of the logic of the PCM). 3

4 10 A/C "ON" SIGNAL 86- FAN SPEED INPUT 41 A/C SWITCH INPUT 93 CONTROL LOGIC INPUT Terminal 93 is from the logic circuit in the air conditioning switch assembly Control Switching (See diagram over) Basic Fan Control Inputs PCM Basic control is achieved by switching terminals 17, (Y/R) 42 (Dk Blue) 46 (Dk Blue/W) and Pin 68 (Dk Blue). The diagram opposite shows the basic A/C inputs into the PCM that control fan speeds. The control switching (see next) is a result of these inputs, particularly terminal 86 - blower motor speed. High condenser fan speed is only achieved on higher blower speeds (ECTsignal can over-ride this control). Basic Control is as follows: PIN 42 is grounded with A/C on - Blower on any speed. This energises relay 2 to supply power to M2. Pin 17 will only be grounded to provide high speed for M2 (dual speed motor). (1900 to 2300 r/min). Pin 46 and Pin 68 control relays 3, 4 for series/parallel switching of the fans to do the BASIC high/low speed switching. These are the MAIN terminals of discussion. For the fans to operate on low speed Pin 46 will be grounded to pull relay 4 contacts open (normally closed relay). With relay 4 open there is no path to earth for M2 other than through relay 3 and M1. Pin 68 is NOT grounded by the PCM on low speed therefore relay 3 is not energised. This allows the M2 to M1 circuit to be completed. With the two motors connected in series both operate on low speed with a voltage drop of 6 volts across each motor. (Presuming the motors are of equal resistance.) Current flow in the circuit is limited by the resistance of both motors. 4

5 High speed switching is achieved by OPEN CIRCUITING Pin 46 (Dk Blue/ White trace) of Relay 4 to DE-ENERGIZE Relay 4. This provides a direct ground for M2. (High speed for M2). AT THE SAME TIME Pin 68 is grounded by the control unit to give M1 a new supply. With M1 being directly grounded we achieve high speed for M1. A full explanation of the operation of dual speed motors (M2 of this system) will be explained in detail in future Bulletins. The operation of dual speed motors is readily controlled by switching circuitry in the PCM - therefore they are becoming common place in modern systems, even though they were dropped in EL models. This is somewhat against normal trends. Strictly M2 is a 3 speed motor in operation. 1st speed is in series switched mode 2nd speed is the parallel switched mode (the condition explained here) 3rd speed is achieved by the PCM grounding Pin 17. This provides an additional supply to M2 to raise its speed from 1900 to 2300 r/min. NOTE: In modifying this circuit (at the technicians discretion) Pin 17 is normally not changed unless the vehicle is operating in extreme conditions of temperature and/or humidity. Our tests have shown 1900 r/min (Pin 17 not grounded) is adequate for all but extreme conditions. Modifying The Circuit As previously mentioned if any circuit is modified the original operational strategies must be maintained. Therefore on modifying the above circuit to gain high speed the principle two circuits that require modification are Pins 46 and 68 (Relay 3 and Relay 4). Pin 46 will require open circuiting to ensure Relay 4 remains closed and Pin 68 (Relay 3) requires grounding to provide a supply for M1. This will require the use of two relays activated by A/C (ie clutch circuit) OR by switching through a medium pressure switch (may be centre switch mode of a trinary switch). No. 3 Relay must be energised by grounding Pin 68 (in parallel with the PCM switching). A normal relay (N/open) taken of the dark blue wire of Relay 3 will provide a ground when the air conditioner is activated OR pressures build to the medium pressure switch setting. Relay 4 (Pin 46 must be open circuited via a normally closed or changeover relay). Activation of the relay is once again done by A/C switch or medium pressure switch. 5

6 EF FAN CIRCUITS B+ FUSE 1 IGN + R DkG Y Y R DkG IGN + RELAY 1 N/OPEN RELAY 2 N/OPEN (Y-R) TO PIN 17 MODULE DIRECT GROUND WILL PROVIDE HIGH SPEED FOR M2 (ADDITIONAL M2 SUPPLY) O O (Dk Blue) TO PIN 42 MODULE DIRECT GROUND WILL PROVIDE FOR LOW FAN SPEED M2 TWO SPEED FAN MI SINGLE SPEED FAN IGN + R DkG Pk-W Pk-W V-Y R DkG IGN + RELAY 4 N/ (Dk B-W) TO PIN 46 MODULE WILL OPEN CIRCUIT TO DE-ENERGISE RELAY 4 TO PROVIDE A DIRECT GROUND FOR M2.[NORMALLY RELAY] B Y B+ RELAY 3 CHANGEOVER (Dk Blue) TO PIN 68 MODULE DIRECT GROUND WILL PROVIDE DIRECT B+ SUPPLY FOR M1 (HIGH SPEED). SUMMARY - EF Falcon 2 SPEED ON FAN 1 (M1) (via series parallel switching) 3 SPEED ON FAN 2 (M2) (via series parallel switching plus dual speed motor) 4 Fan Relays No. 1 = N/open No. 2 = N/open No. 3 = changeover No. 4 = N/Closed To get high fan speed: No. 1 Relay Closed - Y/R into control unit must be grounded. This is only essential if it is necessary to give r/min - if Y/R is not energised we get This is normally enough. 6

7 No. 2 Relay Closed. This is done by control unit in all modes anyway. Air conditioner function of ECU Do not change. No. 3 Relay Must be energised to C/O position (87a to 87) to give M1 direct supply - ground dark blue at ECU (careful there are two dark blue wires) (C228) (Grounding via relay A/C activated). No. 4 Relay Must not energise Open circuit at relay or ECU (Dark blue/white trace). If the circuit is modified (see opposite) the original switching logic of the PCM is retained. Other methods of modification are being used but please ensure the PCM logic is not interfered with. Recommendations for Modification at Technicians Discretion Open circuit dark blue/white trace via A/C activated relay or trinary switch Ground circuit 228 (Pin No unknown) via A/C activated relay or trinary switch. (Dark blue at ECU/relay via A/C activated relay or trinary switch. Optional ground of Y/Red (circuit 752) (Not essential modification.) EL FALCON SWITCHING The EL switching is much simplest using 2 single speed fans and series/ parallel switching of them. Normal PCM control in case of engine overheat etc is the same, therefore modifications to circuits must once again be done to ensure normal switching is maintained. PCM Control Pin 33 and Pin 53 (17 and 68 V8) are grounded by the PCM when required. In fact switching control is via Pin 33 above. Pin 53 (68) is switched with A/C activated under normal operation. When Pin 33 is grounded relays 2 and 3 are energised. Relay 2 provides a direct supply to the RHS motor. Relay 3 provides a direct supply for the LHS motor. 7

8 EL FAN CIRCUIT IGN B+ 15A 100A 60A R-DkG Y PK-W PK-W ALT PIN 53 (DkB-W) RELAY 1 RELAY 2 RELAY 3 V-Y (Dk B) O (Dk B) BK SWITCHING TRANSISTORS INSIDE PCM PIN 33 (Dk B) LHS FAN RHS FAN PIN 53 = PIN 68 ON V8 PIN 33 = PIN 17 ON V8 Modifying the Circuit. Simple!!! Ground Pin 33 (Dark blue at relay 2 or 3 via an A/C or Trinary switch activated relay). Trinary (Medium) Pressure Switching When modifying the EL fan switching, particularly when the vehicle is being used predominantly in highway mode, consideration should be given to switching the fans via a trinary switch. This is simply a matter of placing the switch in the relay coil control circuit to ensure the additional relay only energises when the trinary switch is closed. With EF models Pin 46 requires open circuiting (ie using a normally closed relay), thereby making the incorporation of trinary switch incorporation difficult unless a normally closed trinary switch (medium pressure switch) is sourced ie some Kenworth truck types. 8