So I have a weird problem. When revving the engine the AC stops blowing, the radio shuts off, the interior lights shut off, the dash lights turn off. Battery is 2 months old and I have a new alternator.

Backstory:
2005 Mustang Stage II Roush that is a weekend driver, if best. Could go 3 weeks or month without driving. Needless to say I have to jump start it. Did a jump few weeks ago and drove it to run a few errands. When I parked I noticed "smoke", which turned out to be steam. Overheated! Changed out the thermostat, started it, ran fine, temp was good. Then the battery light came on, car died. Tested the battery and it was bad. New battery under warranty. New battery in still have the battery light and car won't stay running. Checked alternator, bad alternator. Put in new alternator, battery light came back on and so did the ABS and traction light. I revved the engine a bit and the AC stopped blowing, stop revving and the AC came back on. This was last week. So today I go out, jump start it cause the battery is completely dead after sitting for a week. Battery light comes back and when I rev the AC stops blowing, radio turns off, dash lights turn off, interior lights turn off. Stop rev, everything comes back on. No ABS or traction but the battery light is on and the car dies.

I headed now to but a new positive battery terminal connector as I have an aftermarket quick release and thinking it's a bad connection (amp is hooked up to it also). I've done a scan and have no codes. After the terminal I may check relays and all my connections from the alternator change. From there I don't know.

Any ideas?

 

A lit battery light is a faulty charging system.

Most rebuilt/remanufactered alternators are junk. Get a new one from rock auto.. a bit expensive but the reliability is worth it. Check your value first though.

Make certain all of your grounds and your grounding cables are clean and secure. Also make certain your positive cable is in goods condition.

 

Agreed on the rebuilt alternators. I did purchase a brand new one and will be checking connections, fuses, relays. There is obviously something causing and issue with the charging, I just have to find it. Sorry but not sure what you mean by "check your valve first though"?