Instrument cluster keeps rebooting

Volvo,I stand corrected.You are right in that we are not supposed to tap into the vehicles power.There are terminals for hookup on the dash that we are supposed to use.I was unaware of this before I read your comments and then did some research and asked my mechanic some questions.I will have to correct the wiring on Monday so that I am in compliance.Thanks for bringing that to my attention.

Yup . . . many of our class 8 vehicles at work have 12VDC positive and negative terminals right inside the cab

Iā€™m thinking thatā€™s maybe what @1pocket73 was referring to

Be sure the circuit is fused, and the fuse size properly matches the wire size. Youthful me installed a CB radio in my truck, later while getting a load of lumber, had to put some of the small pieces in the cab and disturbed the CB power wiring and started the CB wiring harness on fire! Fuse was too large for the size of the wire.

Wow,that had to be freaky! Probably scared the hell out of you! As it is currently wired I know It is fused properly because I used the factory constant 12v for the main power and pulled the fuse at the box.It did kill power to that line.However,the terminals that they want us to use I am not sure about.After I rerun it on Monday Iā€™ll have to see if there is even a fuse on the line.I think there is because I saw a wire running down the side of the fuse box with a 10A inline fuse on it.That line is probably the one that runs to that 12v positive terminal on the dash.Iā€™m still not sure why the ground terminal is so poor though.Even the ground terminal in the fuse box itself creates horrendous signal noise.