Car won't start. Starter has been tested it is good. Replaced relay. There is a humming sound coming from the a/c vents. Battery is fully charged. No sound when you turn the key.

 

Does the engine crank, rotate, when you try to start engine?
No sound when you turn the key to the "ON" position?
So no fuel pump prime of the fuel rail?
Sounds like more than one issue here
But, you would have to do a little more tests to figure it out.

Have you tried to move gear selector through the gears and back to park?
Did you try to start engine while in neutral?

Do you know how to do a relay by pass test?

 

Tried starting it in neutral. Moved through the gears and back to park. Turn key and it dings that the door is open but nothing when you turn the key. We tried to start it by just squeezing the relay and nothing. New alternator and new battery put in car in February. Not sure how to test to see if it's a bad ignition switch. Is there such a test? Is there a way to test to see if there are other relays that are not working? I appreciate any input. I'm just about over this car!

 

If only we could put our finger on the problem that would be great, but it just doesn't work quite that way.
You will need some type of test equip like a voltmeter or test lite to determine where power is present and where it gets lost..
I realize this may not answer your question, but without a schematic wiring diagram we have to do it the hard way
One way to get to the bottom of the problem is to work back from the starter solenoid and see if power is available there when the key is turned to the start position. if not now we need to go further back to a start relay if the vehicle has one.this can be accomplished with a simple test lite. Without any means to confirm power presence we are working blind. Unless someone comes up with a fast solution, you will need some professional help.

 

The strangest part of this whole thing, is that he started the car, drove it to a different parking spot so it would be under a tree and once he turned it off it would not start again. I'm not sure if he has a voltmeter or test light, but I will check and let him know this is a stumper and only a professional with the right tools can help. Thanks for all the suggestions.

 

Locate the engine bay fuse box. Open it.
Look at the legend on the top or lid of fuse box.
Locate the starter relay.
Try swapping it with another relay.
And try to start engine.
Does it crank?

Can you locate the starter on the engine?
Can you use something to tap the starter while you turn the key to start the engine?
This sometimes helps to move the starter motor out of a dead spot