Sandiegobaymarine Posted September 17, 2016 Share Posted September 17, 2016 Ok so i had a stereo installed on my 57 mack b65 everything was ok then i had a battery go out and i had one of my workers replace them so the truck started but the stereo stoped working we checked all the wires and everything seemed to be in place but the lights were also dim the amp gauge was peged and fuel gauge was peged i thought maby a body ground so i attempted to install a ground between the negitive post and chassie and it sparked so bad its not funny so we were thinking the battery was installed backward so we changed it now the lights were nice and bright but no start we turned the other battery around and it sparked like hell i need a wiring diagram to understand how it transforms from 12 volt to 24 volt start thanks any help is appreciated Quote Link to comment Share on other sites More sharing options...
gearhead204 Posted September 17, 2016 Share Posted September 17, 2016 go to your local napa and have them print of a series parallel switch wiring diagram for you. also if you have the old style voltage regulator you may have to repolarize it after having the batteries in wrong. Quote Link to comment Share on other sites More sharing options...
Underdog Posted September 17, 2016 Share Posted September 17, 2016 Don't forget this truck is positive ground also. 1 Quote Link to comment Share on other sites More sharing options...
j hancock Posted September 17, 2016 Share Posted September 17, 2016 Here is a link to a B61 wiring diagram. Same for a B65. It shows the wiring to the S/P switch. http://www.bigmacktrucks.com/tutorials/article/4-b-model-wiring-diagram/ Quote JimIt doesn't cost anything to pay attention. Link to comment Share on other sites More sharing options...
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