ELECTRONIC CLIMATE CONTROL HEATING IMPROVEMENTS

If an owner of an early 1980 Eldorado or Seville with Electronic Climate Control (ECC) reports a condition of cool or cold legs and/or feet due to insufficient floor heat, this condition can be corrected by performing the following procedure:

ECC Heating Improvement Procedure

1. Check for proper positioning of the instrument panel close-out panels. If these panels are mispositioned, they can block or restrict the normal air distribution from the heater air outlet.

2. Rework the heater air outlet to allow more air to be directed at the driver's feet and legs. To do this:

A. Remove the heater air outlet.

B. Cut out the interior wall and enlarge the left hand opening, as shown in Figure 1. (For ease of removing the plastic material, a soldering iron may be used.)

C. Reinstall the heater air outlet.

3. Check identification color of the ambient sensor base. A beige base color was in production until approximately May 1, 1980. A new sensor was used in production after that date and has a black base color. This new sensor has a different resistance value that will allow the ECC system to control air temperature slightly warmer than indicated on the control head setting when operating in cold ambient temperatures. If necessary, replace the old ambient sensor with a new sensor, P/N 16015606.

The procedures above should completely correct the ECC performance condition to the satisfaction of the owner. If not, the programmer should be checked for proper adjustment as explained below.

Programmer Adjustment Procedure

To assure that the programmer is adjusted properly, it should be calibrated to a standard voltage, as follows:

1. Disconnect the in-car sensor harness from the in-car sensor and jumper the two wires in the connector together.

2. Using Automatic Temperature Control Tester, J-23678, and High Impedance Multi-meter, J-29125, calibrate the A.T.C. Tester to 113 ohms resistance as follows:

a. Remove all harnesses from the A.T.C. Tester.

b. Set the automatic-manual switch to manual on the A.T.C. Tester.

C. Set the slide switch on the multimeter to low - ohms and the calibration knob to 200 ohms.

d. Using the two probes from the multimeter, jumper them to the connector pins shown blacked out in Figure 2. (Note the orientation of the con- nector to assure connection to the proper pin.)

e. With the two probes from the multimeter attached to the proper pins of the A.T.C. Tester connector, turn the manual control knob on the A.T.C. Tester until the multimeter reads 113.0 +/- 1 ohm resistance. Disconnect the multimeter, note the position of the calibration knob, but do not move it. If the calibration knob is moved, it will be necessary to repeat this step.

3. Disconnect the ambient sensor and jumper the leads from ATC Tester J-23678 that are shown blacked out, Figure 2, to the ambient sensor harness.

4. With the ignition in the "on" position, set the control head to "auto" and "75".

5. Measure the voltage at the diagnostic test lead on the programmer (Pin W) with multimeter J-29125 or equivalent. By adjusting the screw on the bottom of programmer, make the multimeter read 3.85 +/- 0.1 volt. (The ECC adjustment screw may be covered with a label.) This reading (3.85 +/- 0.1 volt) is the calibration voltage and the reference point so the temperature of the distributed air is varied correctly to meet customer satisfaction.

If using a meter that is more sensitive than J-29125, the voltage may fluctuate on the meter. This is normal for the system and the technician should average the readings to standardize the programmer voltage.

If the above procedures do not satisfy the owner's comments of ECC performance, the programmer temperature can be adjusted using the procedure in the 1980 Service Information Manual, Page 1B-15.

Technicians should realize that an improperly adjusted programmer can also result in a "lack of cooling" condition in hot ambient temperatures. Most vehicles should be found near the calibration setting under normal operating conditions.

Warranty

For warranty purposes for all of the above procedures, use the following operations and time allowances:

Oper.No. Time Allowance Heater Air Outlet Rework - -------- -------------- Includes R&I Outlet T-6024 .3 hr.

Ambient Sensor R&R D-1200 .2 hr.

Programmer (ECC) Calibrate T-6025 .4 hr.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.