06 freightliner columbia slow crank/no start, followed by no cab power.

Bad Starter ?
Check battery cables
Leave key on and use screw driver to jump it at solenoid on starter

 

slow cranking is more likely a battery but theres a slight chance it could be ur starter

 

Then drop ur starter out get a battery charger and hook the battery charger up to the starter a trick my brother(mechanic) taught me ur ganna have to look up where u put the positive and the negative cable on the starter i cant remember at the moment but dont try and see if it works b4 u drop it bc ur starter can reach 400+ degrees if u push it to hard

 

Could it be the crank sensor? Not sure about Cat's but I know with Detroit's there are two crank sensors that can cause the issues you are talking about. The sensors are about $20 a piece - the labor, well let's just say they were proud of it. Just a thought that may apply to your Cat.

 

Also check for bad ground especially the one on the frame. Freights are known for having that ground wire get dirty and affect the starting......not sure about the fuse situation....kinda sound like you got two wires touching some where. get you a testor and follow the lighter power cord and see if you can find the point of loss of power.....make sure u pay attention to any splices or connectors

 

in '04 freightliner changed power wiring. Before they used two positive wires and two negative wires (as I remember 50 mm2), later and now they use one positive (red) and one negative (black) wires. They are thik, as 75 ore 100 mm2 (exuse me, I use ISO wire gauge marking). Really the problem is ususally with positive wire in battery box ore negative wire bolted on starter. First of all unbolt wires one by one and use steel brush to clear cooper termonals. To find bad connection try to crank engine with starter and toch every connection. Bad connection is usually warm ore may be hot (so I use temperature gun). And I wanna say that terminals may be corroded inside, but it is easy to change.

Other way to find a problem - use VOM with long wires to find voltage drop checking voltage on negative and positive points. It is a way to learn what wire ore connection is bad, negative ore positive....

 

The last two posts here are the answer. Bad main cable connections, likely frame ground to battery cable. I had a service call for a Freightliner with the exact same symptoms, even the loss of cab power after trying to crank. You would have sworn it was just bad batteries. Tried boosting and boosting. Installed 4 new batteries, same problem! I did check all the starter and ground cables, by hand, and they were all tight. I mean, I literally grabbed them with my fist and shook the cable, they were tight. But the electrical connection at the frame stud for the frame to battery cable was arced behind the nut and washer. All it took was backing the nut off 1/2 a turn and re tightening it to re-establish the electrical connection. That sucker fired right up and I felt pretty dumb!