Peterbilt starter issues

Yes. Another piece of equipment...Peterbilt dump truck, believe it is 379. I got a message it is not cranking. At truck, I check batteries, 2 in this unit, both have good voltage, 12.8 and load test good. It would click when dash button pushed. I went to starter and tried jumping the s terminal and battery connection on the solenoid looking thing mounted to starter. It just clicked. I noticed a solenoid on fender well but wasn't sure it's function. I have since read it sends voltage to the starter. I then connected battery positive jump cable to starter motor lug and ground cable to negative lug then touched negative cable to battery negative expecting the motor to run. Nothing. I pulled the starter and cleaned up the terminals and connected battery to starter and remote switch to s terminal and push button. The solenoid clicked a couple of times, the gear didn't move nor motor run. Connected direct to starter motor and touch negative to negative lug on starter. Get a spark but no motor run. I'm using a new battery for these tests am I missing something here? Is this a bad starter? Am I connecting.my cables properly? This huge piece of metal, heavy and cumbersome has me second guessing myself. I checked the resistance between the starter motor positive lug and the ground lug on front of motor. The resistance is 0 ohms . I expected a much higher value. Any suggestions are greatly appreciated.

If your direct on the starter hot and ground it sure sounds like a bad starter to me

You may be able to get a gear reduction starter as replacement and save a lot of lifting weight going back in like lift with one hand light

Check the voltage when you're "clicking", voltage doesn't lie, if the voltage going into the starter is the same as battery voltage, you have a bad starter.

Second that thought about the Prestolite gear reduction starter. Plus, no core charge. Surprisingly good deal for the money, too. Way easier to install.

Remember that a 12 V battery has 2.2 volts per cell. The volt/olhm gauge needs to read 14.2 to mean the batt is carrying a full charge. Anything less is a dead cell.

Maybe 13.2 volts? if the specific gravity is good? Also depends how the batteries load test after the surface charge has been removed

The gear reduction units are nice but don’t last long if started with low voltage. They can’t take the amperage spike. My haul truck has one and I have to keep a tender on it if parked for long periods of time due to all the small draws. A few low voltage cold weather starts and she’s always a slow hard initial crank. Good batteries, good cables and clean terminals.

I just had a similar problem. Replaced the starter and it worked for a few days. Then did it again. When I went through all the cables, the ones to the disconnect in the cab were loose.

It turns out the solenoid on starter was junk. Went ahead and replaced the entire unit. Figured it was all the same age, old. I really didn't want to be pulling that monster out again.

MT42 is not a Bad weight starter, MT 50 was a HOSS, older MT40s were just awkward. Need to try wrestling a MT50 out of a Crawler in dead of winter with snow blowing under your coat. Second a Hard check of charging rate and having batteries Load Tested at a Shop.

For sure on the MT 50!

Those and the original style 15/16 six point 5/8 USS bolts made life less than enjoyable.