2009 Lmtv M1078A1 Charging System

[Mxpert]

New to forum just a quick question if anyone else has seen this problem. No Charge light on in Dash. Replaced Batteries and Alternator new charging at 14.4 volts and 28.2 volts at alternator. And green lights flashing on alternator but no charge light remains on. Thanks for the help

 

[DSD277]

Unless there is an updated dash I'm unaware of (and that is easily possible) , there is no idiot light for the alternator in the display, just the volt gauge to the right of the display

 

[Mxpert]

I am talking about the 2 green lights on the alternator itself one for 12V and 24V. It is a M1078A1 09 new type so that dash picture is even different. In the bottom right hand corner of the digital dash there is also a telltale that shows NO CHARGE.

Thanks

 

[LOGANSTANFORTH]

It's been almost 3 years since I worked on one but I remember there being something about this. **** if I can't remember what it is.

 

[sandcobra164]

I'd question how good your replacement batteries are or if there is an excessive load placed on them. In the National Guard, we run into a lot of dead battery issues due to trucks sitting. I've taken a good truck, for this example a truck with good batteries and charging system, and slaved off a "dead" truck many times and when I disconnect the slave cable, the "dead" truck will stay running but it will disconnect the charging system from the batteries and illuminate the "No Charge" light. Leave them hooked together a little longer and that won't happen most of the time. I've also hooked a good truck to a dead truck with a bad alternator to try and build his batteries back up and had my truck go into the "No charge" mode. It would come out of it in about 5 minutes once disconnected from the "dead" truck. These FMTV's are pretty finicky about their charging systems. I'm a wrecker driver so I operate an M1089 variant and I've seen all kinds of non-sense on these trucks.

 

[bikeracer917]

New to the site. I have a m1078a1 that has electrical problem. The gages on dash stop working.. oil pressure, temp, speedo, and 24 volt gage. The problem is intermittent. Sometimes it will work and sometimes it wont. Any ideas?

 

[bikeracer917]

Hi. Did you ever figure out your charging system problem?

 

[Mxpert]

Bikeracer917 I did receive you PM but could not open. So I will respond here. What I figured out was you need to remove the 2 fusible links under the alternator wires. 12 and 24 volt side, they are bad and should be removed. Also check to make sure that the batteries are properly hooked up. Look at the schematic under the battery box cover. Hope this helps and write back if you need further assistance. MXPERT

 

[bikeracer917]

Thanks for the reply. There are 6 fuse links on the drive end housing of the alternator. It says in the fuse link installation instructions that if they are not installed that it could cause severe damage. Are those the links you were referring to? I don't know of any other fusible links on the alternator. Appreciate any further input. Thanks. Steve. Srtreesurgery@yahoo.com

 

[Mxpert]

No I am talking about the cables that mount directly to the alternator, the 12 and 24 volt DC power cable. They are round washer looking under the cable. This is more if you have battery problems and if they fail you have a constant drain on the batteries. You need a washer to replace it so the hardware will not bottom out. Like I said before check the battery cables and also the battery load control device behind the cab, under the spare tire where the battery cables also route to. Let me know if this helps or you need more info.

 

[Tater6]

I see it's been a year but have you tried to unhook the c.t.i.s harness from the box. I have noticed that once it is unhooked the oil and 24v gauges will start working and the gen /alternator will also start flashing. The harness I belive might be bad. 3 or 4 trucks I have worked on in the last year all have been the same issue. Basically all the control modules should only get about 5 to 7 DC volts. When u see no 24 and no oil the harness is sending 24v to the control modules and the shut down to protect them selfs.

 

[bikeracer917]

Thanks for the reply. I will definitely give it a try. My latest issue is that I think the transmission is stuck in reverse. It won't allow the engine to turn over. I load tested batteries and starter. Tested wtec and tcm. All are good. Engine is not seized. bearings are good and not hydrolocked. Thinking its possible stuck solenoid in trans. Have you ever seen this happen before? If so what was the fix. Really appreciate your help and time

 

[Tater6]

I have one time on a mtv wrecker but it was only after someone did some work on the trans. But I was not apart of the work. I can ask my friend that did the work to find out. When u turn power on does the push button trans says NN correct. It could be the nutral start switch that is bad or a relay on the dash.

 

[Tater6]

But I don't think it keep it from starting. Just kept it from shifting.

 

[bikeracer917]

Yes. The shift button control says NN. It's been a pain in the butt diagnosing. Thanks for your help

 

[Tater6]

So you turn power on you have at least 25v to the starter. You hit the start switch and it only makes a click noise at the starter.

 

[Tater6]

Do you have any transmission codes. Turn power switch in cab on then If you press up and down arrow at the same time it will pull up your diagnostic codes. Example if you have 2 codes it will show d1 then 13. 2nd code will show d2 the the code of let's say 69. So the d# is only a reference to the number of fault codes.
13 ecu input voltage, low/high
69 ecu malfunction. (This one most likely you will need to replace the wtec3 transmission ecu. Same If you get the code of 34 or 36.

To clear codes
press and hold mode button for about 3 seconds little red light should flash 3 times. This clears current codes to clear historic codes press and hold for 10 seconds. Red light should flash 3 times.

 

[bikeracer917]

The starter engages the flex plate but engine won't turn over. Not even by hand.

 

[bikeracer917]

Did have codes. I will post them later. Not at the house where I have them written Down. Really think trans is stuck in reverse.

 

[tennmogger]

I know this is a month old and problem is probably fixed, but... With a torque converter the trans could be locked up but the engine should still turn over. Even if stuck in reverse in the trans, the torque converter would have to be locked also to stop the engine. Two failures is unlikely, IMHO.

Have you monitored the voltage at the starter when you tried to crank engine? With 12 v lighting the 24v starting circuit could be bad and not be noticed, maybe?? Sure sounds like low cranking voltage.