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A Little Help Would Be Appreciated.....

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Rick_bagby

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I am working on a 1995 Stewart Stevenson M1078 A. I am having an issue with the charging system. CB77 is good as is K11 relay. However after about 30 seconds my volts gage drops to 0. I pull either CB77 or K11 and reinstall it, the volts go up to about 27-28 for about 15 seconds, and then drop off to zero again. I have cleaned the terminals on the LBCD, Battery cables are good, and the excitor is still having issues. The red light comes on the voltage regulator, and that is when the volts drop off. Can anyone give me some insight as to where the problem may be? I have tried to by pas the LBCD and unit will not even power up when I hit the green button on the dashboard. This tells me that the LBCD is doing its job. I tried going from battery to excitor. That does not work and it powers up the CTIS directly. I am trying to get this going for a fire department to use so any suggestions would be appreciated.
 
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GeneralDisorder

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Before you do anything else - fully charge each battery out of the truck and test them to ensure they are good.

How did you try to bypass the LBCD? If you hook the 24v batt/load cables together one one stud, and the 12v batt/load cables together on one stud and disconnect it's cannon plug that should eliminate it and everything should work correctly - voltage gauge should read about 0.3v higher without the LBCD in play.

Red light means over-voltage cut-out. I had a similar intermittent issue like that and it turned out to be a cold solder joint on the ground lead for the LBCD inside it's control harness cannon plug.

Review my thread on a similar issue.

2008 A1R with 260a charging questions

Currently has a brand new N3221 voltage regulator (2012 vintage I believe - was new in the box with papers). The truck had a 2013 regulator when I picked it up in Houston. It died about 100 miles from Portland - 2600 miles into the trip back. I put in the brand new spare and drove the last 100...
www.steelsoldiers.com
 
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Ronmar

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Ok, i am a little fuzzy on how a 95 would have a LBCD... 95 =A0, the didnt put the LBCD on till into the A1 trucks a little bit.

If your 12v drops off this would shut off the 24v ign relay K2(powered by 12v). Got a meter? What are the voltages at the 3 power panel test points to the left of the relays and breakers, gnd, 12V, 24V, before and after you turn on the main/ign switch?
 
R

Rick_bagby

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Beaver County Pennsylvania
Ronmar said:
Ok, i am a little fuzzy on how a 95 would have a LBCD... 95 =A0, the didnt put the LBCD on till into the A1 trucks a little bit.

If your 12v drops off this would shut off the 24v ign relay K2(powered by 12v). Got a meter? What are the voltages at the 3 power panel test points to the left of the relays and breakers, gnd, 12V, 24V, before and after you turn on the main/ign switch?
Click to expand...
The LBCD, that is the 4 terminal block that sits just below the air over hydraulic reservoir behind the cab, tucked kind of under the spare tire correct? I maybe calling it the wrong thing. I have not worked on military/NATO vehicles that much. I apologize.
 
R

Rick_bagby

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Beaver County Pennsylvania
Suprman said:
Probably not a 1995. Is the disconnect relay cutting out? Could be lbcd related issue.
Click to expand...
Is that the K11 relay on the print? There a was mouse nest in the PCP when it was brought to me to see if I can get it going. Well I had to go to it because it would not even start. Found a bad aux starter relay and 2 bad batteries. Got those changed and it started up with a little help from a can of starter fluid. starts everytime now with no issues. I leave 2- 12Volt battery trickle chargers on the batteries to maintain the 24 volts and 12 volts. Now if I can get a handle on why the voltage drops out, and can get it back to the Fire Department for usage.
 
Suprman

Suprman

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Bad batteries can cause a voltage spike and shut the alt down but you would still have battery voltage at the dash gauge. Does the truck have a small box to the right of the battery box? There is a low voltage cutoff relay in there. I would also check all the grounds. The main ground cable goes thru a current shunt up by the lbcd. I would remove the shunt and make a good ground connection.
 
R

Rick_bagby

New member
27
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Location
Beaver County Pennsylvania
Suprman said:
Bad batteries can cause a voltage spike and shut the alt down but you would still have battery voltage at the dash gauge. Does the truck have a small box to the right of the battery box? There is a low voltage cutoff relay in there. I would also check all the grounds. The main ground cable goes thru a current shunt up by the lbcd. I would remove the shunt and make a good ground connection.
Click to expand...
No there is nothing by the battery box other than the airline discharge/dryer?? Round cylinder about 10" round and about 18" long. I do not have the SS in front of me but that is my guesstimation?? Battery box, I am well versed in, I do not have the tester in the box. Squiggly cable with a push button hand held stick. Nor do I have a box to the right of the box. All terminals have been cleaned, contact points were sanded, conductive electric grease was applied to: Alternator/Voltage Regulator- 24V and 14V terminals, E Terminal, (and whatever the other terminal is on the voltage regulator) and ground; LBCD - 4 terminals were cleaned and threads chased with the die; Shunt - both ground terminal connections; All ground connections identified in the TM's; lastly - All 8 battery terminals. Knowing that this big boy is going to a Fire Department, the attention to detail for me is a personal must. If you can think of something I missed please do let me know.

So remove the shunt from the equation by mounting both ground lugs to a new ground point? Am I understanding that correctly?
 
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GeneralDisorder

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Rick_bagby said:
According to our mechanic, it is a 3208 Cat.
Click to expand...
Congratulations. You need a new mechanic.

Options are 3116, 3126b, and C7

The 3208 is a neat little engine - 10.4 L V8. Would love to put one in an M1009...... not even close in appearance, number of cylinders, or vintage. Your mechanic....... well isn't.
 
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