ATC System - Prolonged Clicking Noise
TS85-077July 5, 1985
Air Conditioning
1985 MAXIMA AUTOMATIC
TEMPERATURE CONTROL (ATC) SYSTEM
APPLIED MODEL
1985 Maxima
SERVICE INFORMATION
The automatic temperature control (ATC) system on some 1985 maxima vehicles may exhibit a prolonged "clicking" noise during operation, particularly in cold ambient temperatures (50~F or less). To correct this, the Automatic Amplifier Trimmer should be adjusted as described below.
SERVICE PROCEDURE
NOTE: The calibration or matching of the automatic amplifier output voltage to the Potentio Balance Resistor (PBR), requires the use of a digital voltmeter with a scale in hundredths of volts (00.00).
1. Remove the right lower trim panel under the glove box (evaporator-blower motor cover).
2. Locate the PBR Check Connector (two pin, two wire [Y and Y/L] blue connector behind the left side of glove box) (Figure 1).
3. Insert the positive voltmeter probe to the Y/L terminal connector and the negative probe into the Y terminal connector. Set voltmeter scale to read higher than 8 volts (Figure 1).
4. Set the emergency brake and place the transmission selector lever into low.
5. Remove the ash tray (not the bracket) and lower the steering wheel to the lowest position.
6. Remove the 7 screws holding the plastic cluster lid cover to the instrument panel (Figure 2).
7. Carefully pull cover toward the seats, pulling from the ash tray area. With the cover pulled forward, disconnect the cigarette lighter wire harness.
8. Continue pulling and lifting cover up until the upper cover to instrument panel clips separate from the dash. Then, disconnect the rear window defogger connector from the back of the switch.
9. Place the cover on top of the steering wheel.
10. Remove the 4 black machine screws that attach the radio face plate to the radio and remove knobs and face plate. Once the plate has been removed, let it hang by the antenna connector.
11. Remove the 2 upper radio to bracket screws.
12. Remove the two (2) 8mm (socket size) nuts holding the radio assembly to the dash bracket.
13. Remove the 3 equalizer to dash bracket retaining screws located just above the ash tray bracket.
14. Carefully slide radio assembly toward seats. Set assembly on its side on the shift selector indicator. Use a rag to protect plastic surface.
15. Remove the 2 amplifier to bracket screws located on the bottom side of the automatic amplifier.
16. Slide automatic amplifier forward (out of bracket) but do not disconnect the unit from the harness.
17 Turn the ignition switch to the on position. Activate the self-diagnosis system (refer to Service Manual page HA-64, if necessary). Set the temperature set lever (PTC) to 85~F.
NOTE: Before proceeding to the next step, close all windows and doors.
18. Insert a small screwdriver (about the size of a jewelers screwdriver) into the trimmer located on the left side of the amplifier (Figure 3). Decrease voltage until a clicking sound is heard from the DSVV.
19. With the PBR holding the air mix door in the full heat position (fully open), adjust the trimmer (slowly increase the voltage by .01V [volt] increments) until the clicking stops. At this point, increase the voltage by. 05V (+.03V, - .OOV).
EXAMPLE:
If clicking stops at 2.42 volts, then further adjust trimmer to achieve 2.47 to 2.50 reading.
20. Set the temperature lever to 65~F.
21. Move the temperature lever to 85~F and recheck the voltage.
22. Deactivate self-diagnosis and carefully reinstall and reconnect all components.
WARRANTY INFORMATION
CS PNC CT OP CODE FLAT RATE
4R 27032 34 QG10AA 0.8/hr.