2000 mustang windshield wipers worked one day and not the next. it is not a fuse or relay even checked the switch and it is also not the problem

There are two relay's in the under hood fuse / relay box . Wiper relay an wiper relay 2 . Maybe one is bad . also check fuse #14 25 amp. Wiper fuse.Plus the BCM - body control module has a hand in making the wipers work . Are you familiar with automotive electronic control modules ?
The Wiper/Washer System consists of the following components:
• Windshield wiper/washer switch
• Body control module (BCM)
• Wiper micro relay
• Wiper 2 relay
• Wiper diode
• Windshield wiper motor
• Windshield washer pump
• Windshield washer nozzles
• Windshield washer solvent container
• Windshield wiper arm and blade assemblies
• Windshield wiper transmission
• WIP/WASH 10A fuse
• WIPER 25A fuse

Wiper/Washer System Description
The body control module (BCM) controls wiper motor low speed operation. The washer pump and high speed operation are controlled directly by the wiper/washer switch. The windshield wiper/washer switch supplies voltage on the signal circuits to the BCM for windshield wiper/washer operation. When WASH, MIST, DELAY, LOW, or HIGH is detected, the BCM energizes the wiper micro relay by suppling voltage to the relay coil. This allows battery voltage from the WIPER fuse to flow through the relay switched input then through the contacts and out the relay switched output to the wiper 2 relay switch contacts. Since the wiper 2 relay switch contacts are normally closed to the low speed circuit of the windshield wiper motor, the motor will operate at low speed.

Do you have any speed !

The windshield wiper motor is a smart wiper motor with an integrated electronics module. The internal components of the motor are the high/low relay, washer pump relay, and the run/park relay and associated electronics.
The windshield wiper motor receives its inputs from the windshield wiper/washer switch. These signals are ground reference signals. When the switch is placed in different positions, various input signals are selected and sent through circuits to the motor. The windshield wiper motor module identifies these selected input signals and activates the motor to the selected function.!
Your probably going to need a new wiper motor ! ! ! But you should always test before replacing parts !
Visual Inspection Chart Mechanical Electrical

• Windshield washer pump hoses
• Windshield wiper mounting arm and pivot shaft

• Bussed electrical center (BEC) fuse 10 (30A)
• Smart junction box (SJB) fuse 3 (10A)
• Circuitry
• Windshield wiper motor
• Windshield washer pump
• Windshield wiper/washer switch

• The wipers stay on continuously

• Circuitry
• Windshield wiper motor
• Windshield wiper/washer switch

• Go To Pinpoint Test C .

PINPOINT TEST C: THE WIPERS STAY ON CONTINUOUSLY CAUTION: Use the correct probe adaptor(s) when making measurements. Failure to use the correct probe adaptor(s) may damage the connector.
Test Step Result / Action to Take C1 CHECK THE WINDSHIELD WIPER/WASHER SWITCH

• Key in OFF position.
• Disconnect: Windshield Wiper/Washer Switch C2137.
• Carry out the windshield wiper/washer switch component test. Refer to Wiring Diagrams Cell 149 for schematic and connector information.
  
• Does the windshield wiper/washer switch pass the component test?

Yes
GO to C2 .

No
INSTALL a new windshield wiper/washer switch. REFER to Wiper/Washer Switch in this section. C2 CHECK CIRCUITS 56 (DB/OG), 58 (WH), 61 (YE/RD), AND 63 (RD) FOR A SHORT TO GROUND

• Disconnect: Windshield Wiper Motor C125.
• Measure the resistance between the windshield wiper motor C125, harness side and ground as follows:
  
  Windshield Wiper Motor C125 Pin Circuit C125-10 56 (DB/OG) C125-11 58 (WH) C125-1 63 (RD) C125-9 61 (YE/RD)
  
  
• Are the resistances greater than 10,000 ohms?

Yes
GO to C3 .

No
REPAIR the circuit(s). TEST the system for normal operation. C3 CHECK FOR CORRECT WINDSHIELD WIPER MOTOR OPERATION

• Disconnect all the windshield wiper motor connectors.
• Check for:
  • corrosion.
  • pushed-out pins.
• Connect all the windshield wiper motor connectors and make sure they seat correctly.
• Operate the system and verify the concern is still present.
• Is the concern still present?

Yes
INSTALL a new windshield wiper motor. REFER to Wiper Motor in this section. TEST the system for normal operation.

No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
You

First I would look in the fuse box by the driver side and check the fuse,if good then get a meter and see if power is going to wiper motor,if so,then wiper motor is bad,if no power is going to motor,then bad switch,here's a link to see. Repair Guides Windshield Wipers And Washers Windshield Wiper Motor...

Windshield Wiper Switch

Print
REMOVAL & INSTALLATION
The windshield wiper/washer switch is part of the Combination Switch Assembly. Refer to Turn Signal/Combination Switch services procedures.

Check your manual for wiper fuse & relays location.You can inspect fuses visually...hope this helps

On your fuse panel, check the fuse that says ign.it is the 4th one back from the front and is a 40 amp fuse.

Did you ever fix this problem I have a 03 mustang cobra same problem Please help

Mine only has power with switch on high at moter but still wont work any suggestions?

The wipers will not work on my 2000 mustang. I checked the fuse and i wasnt blown.

• Central junction box (CJB) Fuse 211 (15A), Fuse 215 (30A)
• Multifunction switch
• Wiper run/park relay
• Wiper high/low relay
• Windshield wiper motor
• Circuitry
• Battery junction box (BJB)
• CJB
• Generic electronic module (GEM)

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I had a similar problem with a 2000 Dodge Grand Caravan. The windshield wipers turned on when someone turned the heater on in the car. They would not turn off at all, even when the car was turned off and keys were removed from the ignition. The only way to get them to stop is to pop the hood and find the fuse box on the van, and remove the 30 amp fuse for the windshield wiper. After removing the wiper motor and finding it was fine, we discovered the problem was in the relay in the fuse box. This relay is a little black box right next to the windshield wiper fuse and there are two of them, one for on/off and another for speed control. Our On/Off Relay had gone bad and was stuck in the on position, but it sounds like your Speed Control Relay may be bad. A new relay costs ~10$ at an auto part store. Just unplug the old one and plug in a new one, no need to unscrew anything, this was a 1 minute fix.