AC not working correctly

I don't show Concorde until '93 so here's the self diagnostic for 93 ok?
SELF-DIAGNOSTIC SYSTEM Entering Self-Diagnostics 1. Ensure A/C-heater control panel is set to display degrees Fahrenheit ( °F). Start engine (vehicle not moving) and set temperature control to 75 °F. To enter self-diagnostic mode, press and hold floor, mix (floor/defrost) and FRT (front) defrost buttons at the same time. See Fig. 2 . When ATC panel display begins to blink, release all 3 buttons. 2. The display will continue to blink until it completes its tests and calibrations. Any diagnostic trouble codes stored in BCM that are related to ATC will be displayed when blinking stops. If there are no trouble codes, system will return to normal operation. 3. Trouble codes will appear on display in numerical form. Only one number will be displayed at a time. Press panel (vent) button to scroll through any additional trouble codes. See DIAGNOSTIC TROUBLE CODES table for list of codes. Exiting Self-Diagnostics & Clearing Codes To exit self-diagnostics, turn ignition off. To clear codes, disconnect negative battery cable (power supply to BCM) for at least 10 minutes. NOTE: If ATC in-vehicle temperature sensor is disconnected while self- diagnostic system is running, Code 26 will set and display will go blank.

Here's the proceedure for 98':
IN-VEHICLE CALIBRATION & DTC CHECK 1. ATC system door/actuator calibration compensates for mechanical differences in actuators and A/C-heater assembly. Floor, mix and front defrost buttons and blower motor control selector are used for ATC system door/actuator calibration and to check for any ATC system DTC stored in BCM. 2. Set parking brake and place transmission in Park position. Start engine and ensure vehicle does not move. Set ATC control head temperature to 75 °F so that any displayed DTC will not be confused with a displayed temperature. 3. Turn blower motor control selector counterclockwise, to off position. Simultaneously press and hold floor, mix and front defrost buttons. See Fig. 1 . Release buttons when ATC control head display begins to blink, indicating ATC control head has entered calibration/diagnostic mode. ATC control head display will continue to blink until door/actuator calibrations and ATC system DTC check are completed. 4. If ATC system is okay and there are no stored DTCs, system will return to normal operation and temperature symbol "F" or "C" will be displayed. If there is a stored DTC, a two-digit DTC will be displayed. See RETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTICS for BCM DTC identification. To exit calibration/diagnostic mode, turn ignition off. SELF-DIAGNOSTICS * PLEASE READ FIRST * RETRIEVING DIAGNOSTIC TROUBLE CODES 1. Diagnostic Trouble Codes (DTCs) related to the ATC system are stored in the Body Control Module (BCM). Any BCM DTC present, will be displayed on ATC control head display when in-vehicle calibration and DTC check is completed. See IN-VEHICLE CALIBRATION & DTC CHECK under ADJUSTMENTS. ATC control head will display a two-digit DTC. See IDENTIFYING DIAGNOSTIC TROUBLE CODES table. If system is okay and there are no system DTCs present, system will return to normal operation. 2. There are certain conditions in which more than one ATC system DTC can be stored in BCM. ATC control head display can show only one DTC at a time. Press panel mode button to scroll through any additional DTCs. If any other button or selector is moved or pushed, additional NOTE: Changing any ATC control head selector or button position unless instructed to do so, will abort door/actuator calibration and Diagnostic Trouble Code (DTC) check. System will return to normal operation. During in-vehicle calibration and DTC check engine must be running and vehicle not moving. NOTE: There may be DTCs stored in Powertrain Control Module (PCM) that are not related to ATC system DTCs which are stored in Body Control Module (BCM). There are some PCM DTCs that identify problems affecting ATC system operation.
DTCs will not be displayed. To exit in-vehicle calibration DTC check, turn ignition off. CLEARING DIAGNOSTIC TROUBLE CODES DTCs can be cleared from BCM memory using a scan tool or by disconnecting negative battery cable remote terminal for 10 minutes. Negative battery cable remote terminal is located on right strut tower. If using a scan tool to clear DTCs, refer to scan tool manufacturer instructions. NOTE: If in-vehicle temperature sensor is disconnected while Body Control Module (BCM) is operating, DTC 26 will set. This can occur when BCM or ATC control head connectors are disconnected when battery is connected (even with ignition off). To correct condition, clear Code 26 from BCM. See CLEARING DIAGNOSTIC TROUBLE CODES .
10/5/2009 ...

If you cleared the codes, and they dont set again, it will not find any. Does it work right now?

Code 26 is for the inside temp sensor, is that the one you replaced?
TEST 17A: INCORRECT BLOWER MOTOR SPEEDS 1. Turn ignition on and operate blower motor. If blower motor is stuck on high speed, go to next step. If blower motor is not stuck on high speed, replace ATC control head. Perform VERIFICATION TEST . 2. Locate Body Control Module (BCM), attached to junction block, at left end of instrument panel. See Fig. 4 . Turn ignition off. Remove BCM from junction block. Ensure 20-pin internal connector terminals are clean and tight. See Fig. 6 . Repair as necessary. 3. Using an ohmmeter, measure resistance between ground and junction block 20-pin internal connector terminal No. 20. If resistance is less than 5.0 ohms, go to next step. If resistance is more than 5.0 ohms, repair open in junction block ground circuit. Perform VERIFICATION TEST . 4. Using an ohmmeter, measure resistance between ground and junction block 20-pin internal connector terminal No. 1. If resistance is less than 5.0 ohms, go to next step. If resistance is more than 5.0 ohms, repair open in junction block ground circuit. Perform VERIFICATION TEST . 5. Disconnect blower motor power module 4-pin connector. Ensure connector terminals are clean and tight. Repair as necessary. Turn ignition on and engine off. Using a voltmeter, measure voltage between ground and power module 4-pin connector terminal No. 4 (Dark Green wire). If voltage is less than one volt, go to next step. If voltage is more than one volt, repair short to battery voltage in Dark Green wire. Perform VERIFICATION TEST . 6. Turn ignition off. Reconnect blower motor power module 4-pin connector. Connect a jumper wire between ground and BCM Black 24-pin connector C2 terminal No. 6 (Red/Light Green wire). Turn ignition on. If blower motor still operates at high speed, go to next step. If blower does not operate at high speed, replace BCM. Perform VERIFICATION TEST . 7. Turn ignition off and remove jumper wire. Disconnect blower motor power module 4-pin connector. Using an ohmmeter, measure resistance of Red/Light Green wire between BCM connector C2 terminal No. 6 and power module 4-pin connector terminal No. 3. If resistance is less than 5.0 ohms, go to next step. If resistance is more than 5.0 ohms, repair open in Red/Light Green wire. Perform VERIFICATION TEST . 8. Using an ohmmeter, measure resistance between ground and power module 4-pin connector terminal No. 2 (Black wire). If resistance is more than 5.0 ohms, repair open in Black wire. If resistance is less than 5.0 ohms, replace blower motor power module. Perform VERIFICATION TEST .
NOTE: Perform TEST 1A: IDENTIFYING ATC SYSTEM PROBLEMS before proceeding with this test.

VERIFICATION TEST 1. Reconnect all previously disconnected components and wiring. If Body Control Module (BCM) has not been replaced, go to next step. If BCM has been replaced, use DRB (scan tool) to program all Remote Keyless Entry (RKE) transmitters, recalibrate ATC system doors and program other options as necessary. 2. If ATC system has been repaired or battery has been disconnected, ATC door actuators must be calibrated. Start engine and use scan tool to calibrate door actuators. DO NOT allow vehicle to move during door actuator calibration. Turn engine off and go to next step. 3. Turn ignition on. Using scan tool, erase Diagnostic Trouble Codes (DTCs). Turn ignition off and wait at least 5 seconds. Turn ignition on (engine off) and fully operate repaired system to verify correct operation. If system operates properly, go to next step. If system does not operate properly, go to TEST 1A: IDENTIFYING ATC SYSTEM PROBLEMS . 4. If A/C-heater system operates properly, use scan tool to check for other BCM DTCs. If any BCM DTCs are present, go to TEST 1B: IDENTIFYING ATC SYSTEM BCM DIAGNOSTIC TROUBLE CODES test. If no BCM DTCs are present and original DTC cannot be duplicated, repair is complete.

What it boils down to is if the temp reading for outside air temp seems right, then the sensor is OK, your problem is most likley you need to replace blower motor power module.

You have automatic temperature control then it's as stated, if you have a manual a/c system, then it's the resistor.
BLOWER MOTOR POWER MODULE Removal & Installation Disconnect negative battery cable remote terminal, located on right strut tower. Remove lower right underpanel silencer duct. Disconnect blower motor power module connector. Remove blower motor power module. To install, reverse removal procedure. IN-VEHICLE TEMPERATURE SENSOR Removal & Installation Locate in-vehicle temperature sensor aspirator fan assembly at back of ATC control head. Remove ATC control head and remove aspirator fan assembly screws and remove fan assembly. To install, reverse removal procedure. NOTE: In-vehicle temperature sensor is composed of a temperature thermistor and a sensor aspirator fan assembly. Temperature thermistor is serviced as part of ATC control head. If temperature thermistor replacement is required, ATC control head must be replaced.

A/C must be charged enough so the low pressure cutout switch will let it run, also there is a relay for the clutch in the power distribution center(fuse box) under the hood.

Have you checked the charge with manifold gauge set? Most common problem is low charge! Even with compressor not running, it will need a reading of 70-100 psi for compressor to kick in.

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

Please let us know what happens.

Cheers