Where is the constant control ac relay module on 98 mustang gt?

The 98 Mustang GT doesn't have a single, readily identifiable "constant control AC relay module." The AC system's operation is controlled by a network of components, including relays, the PCM (Powertrain Control Module), and various switches and sensors. There isn't a single box labeled as such.

The relays related to the AC system are typically located in one of two places:

* Under the hood in the relay center: This is the most likely location. You'll find a panel with multiple relays; some will be related to the AC compressor (likely marked or identifiable by their size and associated wiring). You'll need a wiring diagram to be sure.

* Inside the passenger compartment fuse box: Some AC functions might have relays here, but this is less common for the main compressor relay.

To find the relevant relays, you'll need:

* A wiring diagram: This is crucial. A factory service manual for your 1998 Mustang GT will have the wiring diagrams showing the location and function of all relays, including those controlling the AC compressor.

* A multimeter (optional but recommended): This will allow you to test the relays to verify if they are functioning correctly.

Without a wiring diagram, identifying the specific relay(s) is difficult and could lead to damaging other components if you accidentally disconnect or replace the wrong relay. Consult a factory service manual or a qualified mechanic for assistance.