I had a friend install a new stereo in my cougar. I go to leave the next day I notice my speedometer isn't working. The next day I notice that it is working but stereo was shut off. What could be the problem?

What is your question?

A friend installed a stereo in my cougar. The next day I start the car and take off then I notice the speedometer isn't working. The next time I get in the car start it take off the speedometer is working but the stereo is now turned off. So if I want a working speedometer I can't have the stereo on. Help

What makes this problem better or worse?

Stereo being turned on no speedometer. Turned off works fine

How long has your 1999 Mercury Cougar had this problem?

For bout a month