cummins 6bt alternator problems

[truecountry]

we got a new to us 90s ottawa yard truck with a cummins 6bt engine (i know this is forestry equipment forum but most all appentice and barko knuckle booms use the cummins 6bt so i firgured i had a better chance here ) it has been hacked bad in wiring ,,,, can anyone help me with the 3 screw on stud wire alternator wiring diagrams not the plug in, right now it has 2 wires running back to the battery and i know that aint right ,, the batt terminal on alternator is empty no wires hooked too it.. i tested the wires and im getting 13.8 on one wire and the terminal marked batt i get 6 volts the other is a ground i think i really didnt get a chane to test it got called away for a breakdown.. if needed i will post pics of alternator and how its wired now

 

[willie59]

We love pics!

 

[truecountry]

ok heres pics of the alternator after i changed the one wire to batt terminal

see the green wire it has blisters on it

 

[truecountry]

and the next pics are a relay that i guess burnt out so the tried to work around it lol

by adding this relay to it

 

[truecountry]

i tested alternator after i rewired it and only got 11.59 volts at batteries,,,,, after 3 hours of working on other break downs i made it back and right away noticed the alternator was hot as h-ll and had been sitting 3hours not running ,im thinking the alternator is shorted out and the relays need to be replaced by what is surposed to be there , not added to....... and i cannot figure out why the relay is needed .. wires from the starter run to it

 

[willie59]

What the heck kind of three ring circus is that! Never seen a cube relay on an alternator circuit before. If I was you, I'd take the alternator to a starter/alternator shop and have them check it out or repair it if need be. They will be able to tell you what connections should be made to it. And I'm thinking if it's done proper...the relay disappears.

 

[Komatsu 150]

What the heck kind of three ring circus is that! Never seen a cube relay on an alternator circuit before. If I was you, I'd take the alternator to a starter/alternator shop and have them check it out or repair it if need be. They will be able to tell you what connections should be made to it. And I'm thinking if it's done proper...the relay disappears.

Just from memory, if you retrofitted an alternator with a built in regulator, that is, not a one wire alternator, into an application that originally had an external regulator you have to kill the field circuit when you turn the key off. The OEM applications had a separate circuit in the key switch to do this. If you don't want to change the switch you have to put in a relay. The circuits have to be divorced from each other when the engine is off. If not, with a diesel, the battery will go dead. With a gas engine the engine will keep happily running with the key off -- and that's how I learned that lesson.

 

[willie59]

Just from memory, if you retrofitted an alternator with a built in regulator, that is, not a one wire alternator, into an application that originally had an external regulator you have to kill the field circuit when you turn the key off. The OEM applications had a separate circuit in the key switch to do this. If you don't want to change the switch you have to put in a relay. The circuits have to be divorced from each other when the engine is off. If not, with a diesel, the battery will go dead. With a gas engine the engine will keep happily running with the key off -- and that's how I learned that lesson.

Are you referring to voltage being produced by the field terminal which keeps the igintion circuit powered up when you turn the key off? When I see that happen, I don't use a relay, I just put a diode in the switched wire to the alternator.

 

[Komatsu 150]

Are you referring to voltage being produced by the field terminal which keeps the igintion circuit powered up when you turn the key off? When I see that happen, I don't use a relay, I just put a diode in the switched wire to the alternator.

A much better solution. I was just speculating as to why a relay might be there. A lot of otherwise good mechanics can't get their head around what those little electrons are doing inside a diode but will install a relay which is more work and has more chance to fail because they can understand what it does.

 

[truecountry]

ok im just as lost as i can be ... got new alternator today .. hooked it up the way i thought it should be and it only charges 11.8 at the alternator by my fluke meter ... now my head is beginning to start hurting... i changed that alternator out with a used one that was on a running knuckle boom loader and same thing 11.8 volts..the big red wires to relay are 2 from starter 1 from alternator i traced them down with my meter ohms..but there are 2 lil wires that plug into it i didnt have a chance to search down but all are factory wires im donig away with the bulls-it ..my head is killing me now ....only information i got today is this truck had a bad short in it , they had to unhook batteries everyday because it would lose charge over nite.. sounds like what yall are talking about i need diode in line ill have to ask yall what size of diode so i can do that and what wire ...but why only charging 11.8 volts is what i cant understand......ive searched under and in cab in dash for any other surprises and nothing... when you hook batteries up there is no spark like you would have with a voltage draw or lights on , nothing worked in cab they had pulled all fuses i replaced all of them ...................can someone send me a simple drawing how this thing should be wired with diode inline

 

[truecountry]

oh i forgot this is a 1993 model piece of equipment

 

[truecountry]

sorry again i called a ottawa dealer and they couldnt tell me anything but the alternator only has 2 wires running to it battery and a ground .....other then that they want me to load it up bring it to them or they will send someone to me ,, i said no thanks

 

[willie59]

A much better solution. I was just speculating as to why a relay might be there. A lot of otherwise good mechanics can't get their head around what those little electrons are doing inside a diode but will install a relay which is more work and has more chance to fail because they can understand what it does.

I got ya there Komatsu 150. I just use a diode in these situations because I'm too lazy to rig up a relay!

sorry again i called a ottawa dealer and they couldnt tell me anything but the alternator only has 2 wires running to it battery and a ground .....other then that they want me to load it up bring it to them or they will send someone to me ,, i said no thanks

truecountry,
I can guarantee you there's a solution to your problem. It's just difficult for us to tell because we can't tell what the posts on the alternator are for. The one thing we know for certain is the large post is the "battery" terminal. It should be connected to the positive battery supply post of the starter. I'm just not certain about the two smaller posts. If it was similar to a "one wire" Delco, it wouldn't require other insulated posts, and I can see in the pic that at least one of them is insulated. Is there any markings on the alternator near the posts, like an "I"? I think I'd unhook wires from the small posts, connect large post to battery post of starter, connect a volt meter so you can monitor voltage, then start engine. Take a jumper wire connected to the battery post of alternator and give one of the small posts a quick touch with the jumper wire. If you don't have a great arc, connect jumper to post again and see what the volt meter does.

 

[truecountry]

there are 4 post... batt ,,,, r ,,,,i,,,and grd......im thinking im reading battery voltage and alternator doesnt know to come on....

 

[willie59]

there are 4 post... batt ,,,, r ,,,,i,,,and grd......im thinking im reading battery voltage and alternator doesnt know to come on....

"batt" is pretty clear. "I" would be and ignition wire from ignition switch. "grd" should be a ground connection. The "R", I'm not sure about. Hook up the "batt" connection to starter battery post. Connect a good ground to the ground post. Start engine. Then put a jumper from "batt" to "I" and see what happens. I know we could thing "R" might be Regulator, but I haven't seen an external voltage regulator used in years, and it wouldn't make sense with the "I" ignition terminal.

 

[Komatsu 150]

This is from Google for a 10SI alternator which has three wires and a ground:

<<The #1 or "R" or Relay Terminal. (Marked with a "1" and "R" on case) This terminal provides a pulsing DC signal that varies with engine rpm. The voltage is half system voltage as measured with a voltmeter. This terminal is used to connect to the dash warning light, or used as a tachometer connection (such as diesel engines that have no ignition system to get a pulse from)>>

That would also explain the relay if there is an idiot light. I don't know if I believe the part about "half system voltage", never heard of that. I'm thinking an old school voltmeter might show half voltage because of the pulsing.

 

[truecountry]

ok im seeing what you are talking about .. but there are only 1 wire from factory wiring harness and thats the battery wire that is shown in pic ,and a grd strap from engine block,, there is no ignition wire... i opened the harness and traced it back a ways

 

[willie59]

This is from Google for a 10SI alternator which has three wires and a ground:

<<The #1 or "R" or Relay Terminal. (Marked with a "1" and "R" on case) This terminal provides a pulsing DC signal that varies with engine rpm. The voltage is half system voltage as measured with a voltmeter. This terminal is used to connect to the dash warning light, or used as a tachometer connection (such as diesel engines that have no ignition system to get a pulse from)>>

That would also explain the relay if there is an idiot light. I don't know if I believe the part about "half system voltage", never heard of that. I'm thinking an old school voltmeter might show half voltage because of the pulsing.

Do one of the terminals connect to an igintion wire Komatsu 150?

 

[willie59]

I looked up the Delco 10SI alternator, that's the old school Delco that uses a 2 wire plug on the side and the battery post on the rear. The last pic that truecountry posted looks more like a 21SI. Check out this link and look at the first alternator pic http://www.alternatorparts.com/FIT_Delco_21SIAlternators.htm. All of these on this page say they're a one wire alternator. truecountry...I think it's time to go to the alternator shop.

 

[Komatsu 150]

I looked up the Delco 10SI alternator, that's the old school Delco that uses a 2 wire plug on the side and the battery post on the rear. The last pic that truecountry posted looks more like a 21SI. Check out this link and look at the first alternator pic http://www.alternatorparts.com/FIT_Delco_21SIAlternators.htm. All of these on this page say they're a one wire alternator. truecountry...I think it's time to go to the alternator shop.

You're right. Sorry to throw in misleading information. Really need to know which alternator it is.