beatngu

Paralell series switch nightmare

39 posts in this topic

So I am trying to figure out how to get the truck to turn over but I have some issues. I did not have an ignition switch for the truck when I bought it but I got this morning to make this whole process easier. When I got the truck the starter was out of it, leaving 3 wires hanging in its place. I bench tested the starter before putting it in the truck and it turns over just fine on 12 V. So I bought 2 new batteries and a new jumper for the two to get 24V and that is no problem. I see there is another place for a battery on the passenger side, which leads to another question. I was using the rear post on the starter as the ground, there is a negative line coming from I believe the solenoid, a negative line to the frame and a positive line with 24V from either a battery or the solenoid. I am so confused, swapping two of the lines there is no voltage going to the solenoid at all but the other way I have 24v to the solenoid. I would like to know if I am supposed to have another battery in the system because hooked up in the configuration where I have no power going to the solenoid I have a reading of 24V between the empty battery terminals on the passenger side of the truck. And the cables on the passenger side of the truck run up to the solenoid/ p/s switch. I do not want to get rid of the p/s switch to make the truck run because I like things original. Any help would be great!

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Go into the the BMT wiki. Go to page 5 of antique and classic info where there is a wiring diagram of what you SHOULD have.

Somebody may have done some creative work on your truck.

Most people rewire to eliminate the S/P switch and all the extra cables. If your existing cables look pretty rough you may want to go this route. Old/bad cables make nice fires.

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Did he have a battery on the drivers side also? Should have 4 large cables to the P Switch. 2 top and 2 bottom.

mike

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Well i have the switch out but it only has two large terminals. but there is also what looks to be a starter solenoid where the other two cables hooked up. i have two batteries on the passenger side and a spot for one more one the driver side

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Well i have the switch out but it only has two large terminals. but there is also what looks to be a starter solenoid where the other two cables hooked up. i have two batteries on the passenger side and a spot for one more one the driver side

If you can......send us some photo's of your project so we can see your issues with this setup.

mike

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Look in my gallery and find photo Mack 213 and see if this photo helps with your setup of the p/s switch.

mike

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I just checked out your pictures and it looks nothing like mine, I will post pictures as soon as I can and toss them up here to give everyone a better idea of what I am working with. But I do know I have a bad ground wire so I bought a whole roll of 2 gauge and some fittings to get rid of all that rotted junk under the cab. I think I can just get rid of the whole 3rd battery setup as well while I am under there...freezing. For a temporary basis I bought a battery disconnect switch so I can just wire the batteries straight to the starter and try to make it turn over that way. Out of curiosity today I hooked my jumper pack to the starter (12V) to make sure the starter turns over and indeed it does but when the teeth catch it won't budge the motor only being 400A of 12V... at least I hope that is it.

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id ditch the 24 volt starter while your under there along with the series parallel switch. a simple 39 or 42MT Delco 12 volt starter and some new cable and two hot batteries will turn that thing over like no ones business.

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Have you ever turned the crank of the motor by hand?

Vlad.

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This is the style S/P switch similar to the one in the wiring diagram in the wiki.

I still advocate that you ditch the switch.

post-7036-0-25976400-1385387662.jpg

post-7036-0-29884500-1385387669.jpg

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Most ALL 24v starters had FOUR 6volt batteries. Two on each side, coming to the S/P switch. That switch hooked them all in series for 24v to start, then back to 2 banks of 12v parrallel to charge. Don't know how they did it with only 3 batteries? Unless they didn't use the s/p switch and just had all three in parallel for 12v starter.

The s/p switch system works, but you need GOOD cables to make it work properly. That is why most guys switch it over. I put up with it the first summer I had my truck, then converted it.

Jim, that does not look like a s/p switch. More like a std solenoid. Not enough large battery connections to hook 4 batteries to that.

This is what mine looked like.

100_3700%20(Medium).JPG

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Hi Larry,

This 12 lbs "paperweight" came out of a B83 cab with all the cables attached. Thought it was the S/P switch. Maybe a solenoid? When I looked at the wiring diagram for the S/P in the wiki it matches with regard to terminal layout. Take a look and see what you think.

I looked at the other wiring diagram for a complete truck in the wiki and it shows the unit with four lugs as shown.

Maybe two different versions of the S/P? The B83 truck did have a 335 Cummins under the hood.

I dunno?

Jim

Just went back and looked again. The style I have is positive ground and the style you have pictured is for negative ground according to the info listed. Don't know why I missed that the first time?

I am still confused so I will stay with 12 volt and NO S/P!

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hmmm, I may need heavier wire then. Well I know what is on my Christmas list now lol. I could not for the life of me figure out the setup in the truck but I guess by switching to 12V and starting from scratch I wouldn't have to care at all about it. I tried turning the motor over with a prybar in the driveshaft for the hydraulic pump and it didn't move too far before I couldn't turn it anymore. I have the pump unhooked now though. We tried push starting it and the truck gave a few puffs of smoke but nothing too promising.

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puff of smoke are better then nothing. at least you know theres fuel getting there

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When using the hand primer I can hear fuel going back into the fuel tank, so could I prime it until hard and try to start it with WD40 or a small amount of ether to try and make it catch?

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id put a 3/4 ratchet and socket on the front balancer bolt of the crankshaft first and make sure you can turn it all the way over without a clunk....... could have been parked cause it has a rod knocking also. I have also had old 673's not turn all the way over because there was a mouse nest on top of #5 piston...... . if it turns over, id prime it up and pull it around with a chain in about 3rd gear direct and see if you can get it to fire off before you go wasting money on batteries and a starter, make sure the engine runs.

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id put a 3/4 ratchet and socket on the front balancer bolt of the crankshaft first and make sure you can turn it all the way over without a clunk....... could have been parked cause it has a rod knocking also. I have also had old 673's not turn all the way over because there was a mouse nest on top of #5 piston...... . if it turns over, id prime it up and pull it around with a chain in about 3rd gear direct and see if you can get it to fire off before you go wasting money on batteries and a starter, make sure the engine runs.

I believe that gets the Best Answer Award thus far Matt. I hope he takes you up on that method first.

mike

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The auxiliary transmission is stuck in gear, not certain which one but the main box comes out and switches just fine. The tractor will not push the truck in 5th. Maybe we will get lucky and the temps will rise above 22 degrees in the next week or two. IF the motor is no good I could always toss the 711T in it...

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If the auxiliary trans. is stuck in gear you can use a long rod and hammer to align shift rods again. I have a Brockway with a 5x4 trans. and if you do not shift the aux.trans. square at times it will lock up.Joe D.

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If the auxiliary trans. is stuck in gear you can use a long rod and hammer to align shift rods again. I have a Brockway with a 5x4 trans. and if you do not shift the aux.trans. square at times it will lock up.Joe D.

I carry a small bar just for that! If I "round" the aux shift and don't work the fuel pedal to get the load off, she jumps to the "no shift" zone...parking brake on, flashers on, jump out, go around to pass side, open door, stand on the fuel tank, pull seat out, pull floor cover up, use the bar on the rails to shift the the trans back to low, replace the floor cover, bang the seat back into it's little tabs, run around and back into the drivers seat and viola! I remember the first time it happened, it was one of my first "emergency" questions to the forum! I dont do it very often anymore! I think I can fix it in less than a minute!

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yup, agree. once the old quadboxes get worn a little its easy to lock it up between gears into the no shift zone in the auxiliary. 5th gear is too high. stick it in 3rd and prime it and give it a yank. if she pops off and runs, lether run, if it sounds good then invest in a starter, some new cable and two batteries.

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