HeavyGunner Posted July 5, 2011 Share Posted July 5, 2011 I am wondering how to hook this set up properly, there is what appears to be a transformer which has two (2) cables coming off of it and then two more cables that go up under the truck. I cannot remember how those cables were hooked up when I messed with the truck about 10 years ago. Any help would be much appreciated. Quote The problems we face today exist because the people who work for a living are outnumbered by the people who vote for a living.The government can only "give" someone what they first take from another. Link to comment https://www.bigmacktrucks.com/topic/19656-battery-hook-ups-on-my-b75/ Share on other sites More sharing options...
Rob Posted July 5, 2011 Share Posted July 5, 2011 I am wondering how to hook this set up properly, there is what appears to be a transformer which has two (2) cables coming off of it and then two more cables that go up under the truck. I cannot remember how those cables were hooked up when I messed with the truck about 10 years ago. Any help would be much appreciated.That is the very old style Delco "845" series/parallel switch. If you look closely at your battery cables the positive post of the cable will have a larger hole in it. One of the positive cables will also run to the frame of the truck. Did the truck as you remember use two, or four batteries? This would make a difference physically, but not electrically how they wired the batteries into the system.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/19656-battery-hook-ups-on-my-b75/#findComment-81205 Share on other sites More sharing options...
HeavyGunner Posted July 5, 2011 Author Share Posted July 5, 2011 (edited) That is the very old style Delco "845" series/parallel switch. If you look closely at your battery cables the positive post of the cable will have a larger hole in it. One of the positive cables will also run to the frame of the truck. Did the truck as you remember use two, or four batteries? This would make a difference physically, but not electrically how they wired the batteries into the system.RobThe truck used two batteries Rob. Also two of the cable ends also have a "P" on them I wasnt sure if this meant Positive or maybe Primary Edited July 5, 2011 by HeavyGunner Quote The problems we face today exist because the people who work for a living are outnumbered by the people who vote for a living.The government can only "give" someone what they first take from another. Link to comment https://www.bigmacktrucks.com/topic/19656-battery-hook-ups-on-my-b75/#findComment-81206 Share on other sites More sharing options...
Rob Posted July 5, 2011 Share Posted July 5, 2011 I have a diagram at the shop I will fax and post to make it easy.If I remember correctly on battery positive post will go to the body of the starter motor. The other post of this same battery will connect to one post of the series/parallel switch. The second battery negative post will connect to the other terminal on the series/parallel switch, and the final terminal will connect to the threaded stud on the starter motor. There is a small jumper wire from one of the battery terminals, (negative, I think) that will attach to a small terminal on the series/parallel switch used for control function. This little wire supplies pull in current for the contactor when you mash the starter button. The main contactor, (internal) will pull a large copper disc against silvered contacts essentially putting the batteries into a parallel configuration and upping the starter voltage to 24VDC to spin the starter motor. Upon release of the starter button, the contactor releases and and batteries are once again put in a parallel configuration for 12VDC operation.My memory isn't quite what it used to be but that seems to be the way I remember it.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/19656-battery-hook-ups-on-my-b75/#findComment-81207 Share on other sites More sharing options...
HeavyGunner Posted July 5, 2011 Author Share Posted July 5, 2011 If you look at the first picture (the top view of the battery) and zoom in it appears the top right cable and the bottom left cable are the ones marked with a "P". Quote The problems we face today exist because the people who work for a living are outnumbered by the people who vote for a living.The government can only "give" someone what they first take from another. Link to comment https://www.bigmacktrucks.com/topic/19656-battery-hook-ups-on-my-b75/#findComment-81208 Share on other sites More sharing options...
Rob Posted July 5, 2011 Share Posted July 5, 2011 This computer does not have good resolution and I'm half blind anyways........Look at the size holes in the cable ends. Positive is always larger than negative. Always has been on a top post cell.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/19656-battery-hook-ups-on-my-b75/#findComment-81210 Share on other sites More sharing options...
HeavyGunner Posted July 5, 2011 Author Share Posted July 5, 2011 I have a diagram at the shop I will fax and post to make it easy.If I remember correctly on battery positive post will go to the body of the starter motor. The other post of this same battery will connect to one post of the series/parallel switch. The second battery negative post will connect to the other terminal on the series/parallel switch, and the final terminal will connect to the threaded stud on the starter motor. There is a small jumper wire from one of the battery terminals, (negative, I think) that will attach to a small terminal on the series/parallel switch used for control function. This little wire supplies pull in current for the contactor when you mash the starter button. The main contactor, (internal) will pull a large copper disc against silvered contacts essentially putting the batteries into a parallel configuration and upping the starter voltage to 24VDC to spin the starter motor. Upon release of the starter button, the contactor releases and and batteries are once again put in a parallel configuration for 12VDC operation.My memory isn't quite what it used to be but that seems to be the way I remember it.RobGreat, cant wait to see the diagram. Then I can try and start the beast. Quote The problems we face today exist because the people who work for a living are outnumbered by the people who vote for a living.The government can only "give" someone what they first take from another. Link to comment https://www.bigmacktrucks.com/topic/19656-battery-hook-ups-on-my-b75/#findComment-81211 Share on other sites More sharing options...
HeavyGunner Posted July 6, 2011 Author Share Posted July 6, 2011 Well Rob I looked at the cable ends this afternoon to see if I could find the bigger inside diameter positive cable ends and the two biggest ends are the ones that hook to the parallel switch. Does that sound right? I am still fingering through the service manual that I found to see if I can find anything. Quote The problems we face today exist because the people who work for a living are outnumbered by the people who vote for a living.The government can only "give" someone what they first take from another. Link to comment https://www.bigmacktrucks.com/topic/19656-battery-hook-ups-on-my-b75/#findComment-81244 Share on other sites More sharing options...
rhasler Posted July 6, 2011 Share Posted July 6, 2011 Try this:http://www.bigmacktrucks.com/index.php?app=tutorials&article=4 Quote "Mebbe I'm too ugly and stupid to give up!" Link to comment https://www.bigmacktrucks.com/topic/19656-battery-hook-ups-on-my-b75/#findComment-81246 Share on other sites More sharing options...
HeavyGunner Posted July 6, 2011 Author Share Posted July 6, 2011 Try this:http://www.bigmacktrucks.com/index.php?app=tutorials&article=4Thanks for the schematic, I do have a couple of questions though. On the schematic how do you differentiate the positive and negative cables? My second question is will this diagram still use the same wiring principles even though my truck takes two (2) 12v batteries instead of four (4) 6v batteries? Quote The problems we face today exist because the people who work for a living are outnumbered by the people who vote for a living.The government can only "give" someone what they first take from another. Link to comment https://www.bigmacktrucks.com/topic/19656-battery-hook-ups-on-my-b75/#findComment-81247 Share on other sites More sharing options...
Mike Posted July 6, 2011 Share Posted July 6, 2011 Thanks for the schematic, I do have a couple of questions though. On the schematic how do you differentiate the positive and negative cables? My second question is will this diagram still use the same wiring principles even though my truck takes two (2) 12v batteries instead of four (4) 6v batteries? your cable ends for the positive should be a larger hole than the negative ends that connect to your batteries. yes the diagram will be for either set up. the four batteries are for four six volt batteries where the two 12 volt batteries are not put together in series. mike Quote Link to comment https://www.bigmacktrucks.com/topic/19656-battery-hook-ups-on-my-b75/#findComment-81249 Share on other sites More sharing options...
Rob Posted July 6, 2011 Share Posted July 6, 2011 Well Rob I looked at the cable ends this afternoon to see if I could find the bigger inside diameter positive cable ends and the two biggest ends are the ones that hook to the parallel switch. Does that sound right? I am still fingering through the service manual that I found to see if I can find anything.It does not sound correct. I suppose this would work if one were placing two 12VDC batteries in parallel utilizing a negative ground but this doesn't make any sense as explained.Look again at the battery cables and find one that attaches to either the frame of the truck, or body of the starter motor itself. This attachment on the starter motor could be one of the retention bolts into the bellhousing, or the motor itself. This attachment point will not be an insulated point as it most ground the engine. Most starter motors utilizing a "Dyer" type drive will have a copper stud that is insulated from the starter motor housing where current and voltage is applied to spin the starter motor itself. You must have both a positive, and a negative battery post tied to the series/parallel switch in order to generate the 24VDC needed to spin the starter motor. The truck itself with the exception of the starting system is 12VDC. This could have a variance as if the truck were ex military, or possibly fire apparatus which could be 24VDC electical systems complete. I don't know this variable but assume it does not apply.I just looked at your photos and the battery cables do appear to be connected correctly. I probably would not use them as is as they are in bad condition. If you don't have good tight, clean connections, something will probably fry when you mash the starter button. These were some tempermantal SOB's so you need to take precautions accordingly. Looking at your first photo: the post on the left is physically smaller than the one on the right. I can see where the cable runs and attaches to the s/p switch. This is a good start. You just need to follow as mentioned earlier. Your trigger wire, (small wire) is also connected correctly. I'd get everything cleaned up, install known good batteries and give it a go. You may be surprised, you may be dissappointed, but everything looks in order from this vantage point.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/19656-battery-hook-ups-on-my-b75/#findComment-81259 Share on other sites More sharing options...
HeavyGunner Posted July 7, 2011 Author Share Posted July 7, 2011 Ok, if time permits I may mess around with the truck for a couple hours and see what i can come up with. Thanks for all of your insight and info on this matter Rob. Quote The problems we face today exist because the people who work for a living are outnumbered by the people who vote for a living.The government can only "give" someone what they first take from another. Link to comment https://www.bigmacktrucks.com/topic/19656-battery-hook-ups-on-my-b75/#findComment-81286 Share on other sites More sharing options...
Rob Posted July 7, 2011 Share Posted July 7, 2011 Ok, if time permits I may mess around with the truck for a couple hours and see what i can come up with. Thanks for all of your insight and info on this matter Rob.I think I remember where that diagram is now. I'll look tonight at the shop.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/19656-battery-hook-ups-on-my-b75/#findComment-81295 Share on other sites More sharing options...
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