i put in anew battery and alternator and it will not hold a charge. on 2005 Chevrolet Colorado

i checked all fuses and i guess i will have the alternator checked, but is brand new. i can figure this one out.

Have the alt checked while on the truck, output voltage at the battery post should be 13.5 to 14 @ idle with lights & heater on!
thanks there old pushrod, wil check this out. Thanks| let you know how this works out. jedredrock12
1 more answer
With the vehicle turned off, Touch the voltmeter to black on battery and the red to the connection at the alternator. If the read is 0 then you have a break between the alternator and battery. Follow the red wire from alternator to the fuse box. Is it possible the fusible link has burnt out at the fuse box.