Which relay under the hood on a 97 ford Aerostar controls horn and cruise control?

There isn't a single relay in a 1997 Ford Aerostar that controls *both* the horn and the cruise control. They are controlled by separate relays and potentially other components. You'll need to consult a wiring diagram specific to your Aerostar's year and trim level to pinpoint the exact relays.

To find the correct relays, you should:

1. Consult a repair manual: A Haynes or Chilton repair manual for your specific vehicle will have wiring diagrams and relay locations. This is the best and most reliable method.

2. Use a wiring diagram online: Some websites offer free wiring diagrams, but ensure the diagram matches your exact year and model. Be cautious, as accuracy can vary.

3. Examine the underhood fuse and relay box: Carefully examine the labels on the relays in the underhood fuse box. Some relays might have descriptions hinting at their function (though it's not always comprehensive). You might find separate relays labeled for the horn and cruise control.

Trying to diagnose this without a wiring diagram is difficult and could lead to misidentification and damage. Using a wiring diagram is essential for safe and effective troubleshooting.