2005 mazda6 wont start new alternator, battery, and starter

try this its a common problem over time. http://www.underhoodservice.com/no-start-no-crank-mazda6-engine/

Check all the electrical connections . grounds and to starter. One of them are bad or the new starter crapped out on you. Remember just because it is new doesn't mean it is good. I have got new items that were junk out of the box.

Elaborate please. Does the starter turn the engine over? Does the start not even turn?

I'd check for bad or corroded contacts/cables from battery to starter (If your vehicle is older than 14 years). If that looks good I'd be suspicious of the solenoid in your starter sticking(will probable need a new starter).

Check starter relay and kick starter

Hi, unfortunately your voltage regulator is controlled by the PCM. If the 120 amp charge fuse is good and the alternator is good; then the PCM is probably bad, as your mechanic is suggesting.

will it start with a jump? check battery for full charge, maybe alternator is not charging, check battery connections all the way down to starter, check selonoid by cross jumping terminals to engage starter.

did you check all the fuses and the main fuse under the bonnet try to give thr starter a few taps with hammer not hard if starts then it is brushes in starter ,does light come on on dash if you put key in on position

Most likely the alternator,chech for loose connections at the alternator first, if you have access to a voltmeter you can easily check this.Get the car started and place the leads to the battery terminals,if the alternator is good you should get about 14.8 v at idle and it will go as high as 15.5v to 16v as you rev the engine up.Anything between 12v and 14v at idle indicates a weak or not operating alternator.If you get a good reading run it for a bit and then see if it will start again,if it wont start check the battery cables(especially the negative) for corrosion or loose connections,look for cuts or tears in the insulation or a bulge in the cable wich will indicate corrosion under the insulation.If everything else checks out good and it still won't start then you'll need to look towards the starter.

This sounds like a starter problem, does it click when you hit the key? are the battery cables ok, not corroded?