How to find/identify bad connections in house wiring?
The only way I would know how to do it is to go and buy an inexpensive Infrared Thermometer. You can buy them anywhere for less than $60.00. Then you can walk through and "site" any device that appear to be warmer than normal. Start with you panel and survey every breaker. Then you can go to every device and check it. Did I mention you should make sure the circuit is on a load for at least an hour. I would use a small 1500W heater for a load source on receptacles. This is something you can do over time. If you are just shooting a receptacle head or an AC disconnect the temperature should rise to at least 5 - 10 degrees above normal temp. Really loose connections will rise much more than that.