hicrop10 Posted April 3 Author Share Posted April 3 Having a problem,when I checked my electrical system everything is hot on the truck.I touch the steering column with the test light and it light up hot .What am I doing wrong Quote Link to comment https://www.bigmacktrucks.com/topic/73175-mack-b873sx-restoration/page/13/#findComment-594063 Share on other sites More sharing options...
ekennedy21 Posted April 3 Share Posted April 3 6 hours ago, hicrop10 said: Having a problem,when I checked my electrical system everything is hot on the truck.I touch the steering column with the test light and it light up hot .What am I doing wrong Positive ground? Quote Link to comment https://www.bigmacktrucks.com/topic/73175-mack-b873sx-restoration/page/13/#findComment-594098 Share on other sites More sharing options...
hicrop10 Posted April 3 Author Share Posted April 3 Yes Quote Link to comment https://www.bigmacktrucks.com/topic/73175-mack-b873sx-restoration/page/13/#findComment-594104 Share on other sites More sharing options...
skydawg Posted April 4 Share Posted April 4 Short somewhere...start pulling fuses/breakers til the light goes out to isolate the short. Quote Link to comment https://www.bigmacktrucks.com/topic/73175-mack-b873sx-restoration/page/13/#findComment-594114 Share on other sites More sharing options...
mechohaulic Posted April 4 Share Posted April 4 On 4/3/2026 at 11:11 AM, hicrop10 said: Having a problem,when I checked my electrical system everything is hot on the truck.I touch the steering column with the test light and it light up hot .What am I doing wrong one set of batteries hooked up improper?? disconnect one set at a time AT THE BATTERIES . see if a difference. one set incorrect will narrow down the search . Quote Link to comment https://www.bigmacktrucks.com/topic/73175-mack-b873sx-restoration/page/13/#findComment-594119 Share on other sites More sharing options...
Popular Post tjc transport Posted April 4 Popular Post Share Posted April 4 if the alligator clip is hooked to the negative post of the battery, everything metal/connected to the frame will show powered on a positive ground system. you need to connect the alligator clip to the POSITIVE terminal of battery to check power on a positive ground system. 4 Quote when you are up to your armpits in alligators, it is hard to remember you only came in to drain the swamp.. Link to comment https://www.bigmacktrucks.com/topic/73175-mack-b873sx-restoration/page/13/#findComment-594121 Share on other sites More sharing options...
mowerman Posted April 4 Share Posted April 4 You know it’s been so long since they messed with a positive ground. I really don’t have any advice even though mine is I really don’t remember anything about it if I had to hook something up myself, I would probably have you come here for advice. Good luck to you. Hope you get it figured out. I’m thinking you got a wire touching something. Quote Link to comment https://www.bigmacktrucks.com/topic/73175-mack-b873sx-restoration/page/13/#findComment-594123 Share on other sites More sharing options...
hicrop10 Posted April 4 Author Share Posted April 4 2 hours ago, tjc transport said: if the alligator clip is hooked to the negative post of the battery, everything metal/connected to the frame will show powered on a positive ground system. you need to connect the alligator clip to the POSITIVE terminal of battery to check power on a positive ground system. I will try your thoughts tomorrow morning,when I get back to it. Quote Link to comment https://www.bigmacktrucks.com/topic/73175-mack-b873sx-restoration/page/13/#findComment-594125 Share on other sites More sharing options...
Popular Post hicrop10 Posted May 2 Author Popular Post Share Posted May 2 Got the front shutters installed,generator rebuilt and installed. 6 Quote Link to comment https://www.bigmacktrucks.com/topic/73175-mack-b873sx-restoration/page/13/#findComment-595385 Share on other sites More sharing options...
hicrop10 Posted 3 hours ago Author Share Posted 3 hours ago Since I’m converting my truck over to negative ground i will no longer need the generator (just rebuilt),voltage regulator (new),series parallel switch new,and the 24 volt starter.If anyone is interested let me know. Quote Link to comment https://www.bigmacktrucks.com/topic/73175-mack-b873sx-restoration/page/13/#findComment-596187 Share on other sites More sharing options...
Geoff Weeks Posted 3 hours ago Share Posted 3 hours ago Those large case generators aren't that common anymore, and in my mind are of value. I have 2 12 volt and 1 6 volt so don't need more. If it were I, I'd keep the generator (period correct and 50 amps is plenty) as it will work just as well on either polarity. But that is just me. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73175-mack-b873sx-restoration/page/13/#findComment-596189 Share on other sites More sharing options...
hicrop10 Posted 2 hours ago Author Share Posted 2 hours ago Tks Geoff,my only problem I’m having is mounting the alternator that was given to me.My tuck has the Cummins in it and will have to do a little backyard engineering to make a bracket. Quote Link to comment https://www.bigmacktrucks.com/topic/73175-mack-b873sx-restoration/page/13/#findComment-596192 Share on other sites More sharing options...
Geoff Weeks Posted 2 hours ago Share Posted 2 hours ago (edited) I might have a Big Cam alternator mount. what does your big cam have on the front of the engine. Big Cam 3 should have duel belt sheeves behind the damper for alternator drive. am I mixing you up with another guy who has a Big Cam 3 and you have an old Cummins? Edited 2 hours ago by Geoff Weeks Quote Link to comment https://www.bigmacktrucks.com/topic/73175-mack-b873sx-restoration/page/13/#findComment-596197 Share on other sites More sharing options...
hicrop10 Posted 2 hours ago Author Share Posted 2 hours ago Mine has an old Cummins 335.It a single belt,the spread of the mounts on the motor is 9”.I can’t get you a picture of the mounts tomorrow. Quote Link to comment https://www.bigmacktrucks.com/topic/73175-mack-b873sx-restoration/page/13/#findComment-596199 Share on other sites More sharing options...
Geoff Weeks Posted 2 hours ago Share Posted 2 hours ago Ok, I am mixing up two people with old Red Macks with Cummins in them! I have Big Cam mounts that are yours for the postage but don't think it will work with your set-up Quote Link to comment https://www.bigmacktrucks.com/topic/73175-mack-b873sx-restoration/page/13/#findComment-596200 Share on other sites More sharing options...
Geoff Weeks Posted 2 hours ago Share Posted 2 hours ago 47 minutes ago, hicrop10 said: Tks Geoff,my only problem I’m having is mounting the alternator that was given to me.My tuck has the Cummins in it and will have to do a little backyard engineering to make a bracket. A word to the wise, make the mount 2x-3x more stout then you think it needs to be. Delco recommends 3/8" plate for making mounts. I found that it needs to be at least that thick and firmly mounted to the engine to prevent it from breaking. As I stated earlier, you can keep that rebuilt generator as is and it will do the job just fine. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73175-mack-b873sx-restoration/page/13/#findComment-596201 Share on other sites More sharing options...
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