2005 KW T600 looses power and randomly shuts off.

Definitely low washer fluid.

 

You have to hunt the electrical problem down. Start with cleaning all the main electrical connections. I would start with the main ground connections clean them up & make sure they are tight.

 

...low blinker fluid

 

Pretty sure your wrong .. I bet the brake light fluid needs to be changed especially if it has LED brake lights their very sensitive to that and if the fluid is dirty it will send electrical Gremins through the whole electrical system

 

Also power feed to fuse panel, it is a pass thru connector on bottom side of fuse panel accessed from firewall side. It is just a battery terminal nut.

 

Your voltage issue sounds like a buddy who had the kw clean power system APU. His alternator was well over a $1000 and he would have to randomly do a key off then on in gear while he was rolling to start the alternator charging again . He ended up converting to a normal alternator from the deep cycle one and problems went away.

 

I liked it better when my biggest problem was having to turn most of the chicken lights off to run the heater. An 80amp alternator was only going to do so much. This new stuff is just too complicated.

 

All those problems do not fit together as one cause to me however.
Is the speedometer thing all the time? If not does it only loose power when the speedometer is messing up. When it looses power is it limited to a lower than normal max RPM.
The low voltage gauge reading and shutting down sounds like a bad ground or power supply as others have mentioned. Those can be hard to find at the shop when the problem is not occurring. I suggest the KISS program. Keep it simple Samantha. Get an old school test light with a light bulb. When it shuts down in a safe place you can coast to the side do that. Do not turn the key or lights off. DO NOT UNDER ESTIMATE UNEVEN PAVEMENT OR THE SHOULDER. You have no power steering.
Then use your test light between the battery ground and frame, ground and cab, frame to ground stud on starter, frame to engine. You have to be sure to get past the rust paint and such. The light should never even dim glow but in you case I expect it to light. If you find where the light lights a decent can correct it in short order.
The positive side works the same way but is a little more challenging to test.