A/C - System Repair
88mazda01Category Applicable Model/s Subject Bulletin No. 056/88
15 1986-1988 RX-7 HEATER & A/C SYSTEM REPAIR Issued 1/13/88
Revised
DESCRIPTION
There are three basic areas to check if this system is malfunctioning:
1. Logicon Unit Check with Logicon Checker and voltmeter.
2. Heater Amp Control Box Check according to Service Bulletin, Category 15, No .037/86.
3. Motorized Actuators (air mix. mode control, REC-Fresh) Check using Ohmmeter, voltmeter and physical inspection.
Since the Logicon unit is often replaced when the actual problem is elsewhere in the system, be sure to check all three major areas BEFORE replacing the Logicon.
1. CHECKING THE LOGICON
IMPORTANT NOTE:
The Logicon Checker tests only the Logicon, and will NOT indicate problems in the actuators or heater amp control box. Nor will this checker indicate problems with signals going to the actuators.
The Logicon can be checked using the Logicon Checker and voltmeter as per procedures listed in the Workshop Manual. However, some problems with the system often are NOT caused by the Logicon unit itself. Actuator problems, etc. possibly may feed back into the Logicon and cause damage. In such cases, a damaged Logicon may be a symptom, but not the real cause of the problem. Therefore, before replacing a Logicon, check other areas of the system.
Signals sent to the actuators from the Logicon are simply either 12 volts or ground. The 12V signal starts whenever a button or lever is moved. For example, signals to the air mix actuator must be checked while moving the temperature control lever. Once the actuator reaches the proper position, the signal stops. (However, if the temperature control lever is at the highest or lowest position, the 12V signal continues to be sent to the actuator.) These signals can be checked with a voltmeter or test light. Ideally, a polarity tester which indicates whether current or ground exists may also be used.
The main connector to the Logicon unit is located under the trim panel at the inside base of the windshield. This connector can be reached easier and faster by removing the trim panel.
2. CHECKING THE HEATER AMP CONTROL BOX
The time to check the heater amp control is when there is a problem with blower speed during heater or A/C operation. The heater amp control box attaches onto the Logicon unit itself. Therefore, to reach the amp control box, you must remove the Logicon unit.
[Complaint] Blower fan does not go to full high speed or speed is too slow or operation is erratic.
[Check/Repair] Replace heater amp control as per Service Bulletin, Category 15, No .037/86.
3. CHECKING THE AIR MIX ACTUATOR
The air mix actuator connector can be reached from under the dashboard, to the left of the center console. This actuator is a combination servo motor and position sensor. The actuator "parks" at certain positions based on the position of the temperature control slide lever. If the links to the actuator are bent, restricted or attached in the wrong position, the actuator may be prevented from stopping at the proper position, thus resulting in internal damage. Proper positions can be verified as per workshop manual procedures. The G/W and Y wires alternately provide power and ground from the Logicon to operate the servo. The remaining 3 wires send signals to the Logicon according to the position of the air mix temperature door.
[Complaint 1] A/C operates normally, but suddenly goes to heat. May return back to A/C again for no apparent reason (without touching controls). May occur either intermittently or on a regular basis. Also may occur in opposite (heater to A/C).
[Check/Repair 1] Check air mix actuator, connector, actuator link. Be sure link and heater water valve do not restrict actuator movement. If above factors check "good" but problem persists, problem may be internal. Replace the actuator with the new one.
[Complaint 2] Air volume is correct and comes out of proper opening, but is not heated properly or is always hot.
[Check/Repair 2] Check the following:
1. Air mix actuator
2. Rod links
3. Water valve
4. Clearance of wires
Be sure air mix moves heater water valve while the temperature control lever is moved. If movement is correct, problem is likely either in heater valve, cooling system, or heater core. If movement is NOT correct, check connector, link, servo motor, etc. If actuator does NOT move, disconnect G-04 connector, jump 12V at the motor side to B/W terminal and ground Y terminal (then reverse ground and power). If the motor is good, it should operate in one direction and reverse as 12V and ground are reversed at the terminals.
At the harness side connector, measure voltage and check ground at B/W and Y wires. If voltage cannot be measured or ground is not present, problem is on Logicon side.
If motor attempts to move, but cannot, check for stuck heater valve and/or binding linkage.
Now check resistance of Br/R and Lg/r at the air mix actuator harness. Resistance should change according to position of air mix temperature door.
If actuator still does not operate properly or fail checks listed above, replace actuator with new one.
NOTE:
The air mix actuator will not operate properly or can be damaged if any of the following occur:
1. Mis-aligned, improperly positioned, or bent rod links
2. Sticking water valve
3. Improper attachment of electrical connector.
Also remember that possible damage to the Logicon itself may result from feedback due to conditions listed above. In such a case, a damaged Logicon is merely a symptom, not necessarily a cause of the problem. Replacement of the Logicon without further checks of the system may only result in another damaged Logicon.
If the three areas check out "good", the problem is elsewhere in the system. Check resistor, blower, etc. according to procedures listed in the Workshop Manual.