OK got your message on the other post (About the van) I am assuming that your Voyager is equipped with Automatic Climate Control. Follow the instructions below and you will get a better idea of what is wrong with your system.
1. To enter calibration/diagnostics test, set parking brake. Start and warm engine to normal operating temperature. With engine idling, turn blower switch to high. Turn mode switch to panel. Open all outlets. Move temperature to full cold.
2. Press and hold rear wash and rear wiper buttons simultaneously for 5 seconds (Until ALL LEDs illuminate). All LEDs should illuminate for 5 seconds. Rear wiper and intermittent rear wiper button LEDs will flash alternately during calibration/diagnostics test.
3. After approximately 60 seconds, if only the rear wiper button LED is flashing, calibration is successful and the system is okay. If rear wiper and intermittent rear wiper button LEDs are flashing, Diagnostic Trouble Codes (DTCs) are present. (See "Reading Diagnostic Codes" below)
4. To exit calibration/diagnostics test at any time, press the rear window defogger button, rear wiper button, or cycle the ignition off and then on. Test will automatically terminate 15 minutes after calibration/diagnostics is entered.
Reading Diagnostic Codes
1. Perform calibration/diagnostics test. If a DTC is present after calibration/diagnostics test has been performed, system will flash rear wiper and intermittent rear wiper button LEDs in sequence. Rear wiper represents code level, and intermittent rear wiper button LED represents code value.
2. Each time the rear wash button is depressed, rear wiper button LED wil cycle to the next code level in numeric sequence. After code level 5 is reached, rear wiper button LED will cycle back to code level 1. See table below.