2005 dodge magnum wont start error code p0645 what do i do

Question

lights and dash work fine check engine light blinks when i turn key on and when i try to crank it i here a click sound from the rear  power distribution box error code p0645

Answer 1

P0645 A/C clutch relay circuit

This code is for the A/C relay. If the a/c clutch ever shorts out it take out fuse 20, that fuse also power the starter relay. very slim that this would be the problem . This condition with a no crank is very problematic to Dodge, to a problem with the integrated power module to a ignition switch that tends to rotate out of position to just a faulty starter, You will have to rule out a starter by direct connection to see if it  works, You can try this it works and help pin point the problem hold the ignition in the crank position for a period of time if it then cranks , you need to test the ignition switch , also this year some have fusable link to the starter from its battery terminal