Just another alternator charging, battery thread - help for new owners?

[Third From Texas]

Driving it to a Auction this morning to see how people react to it. Not being sold there just a lot of people know me and not seen the truck yet.

Yeah, enjoy that part while it's fresh.

After the 200,000th time you say "no, it's not a Unimog" it starts to get a bit old.

Now when people ask where I got it I just say "You know that National Guard post over on Weber and Mc Ardle? Those guys never lock their gates"

 

[Ronmar]

Doesn't this connection connect the 12/24VDC Negative to the Starter and then the braided goes to the Frame? Course the starter is bolted to the engine to for another path. Either way seems this is a important connection to be good for a lot of reasons.

Yes it does, and that strap is probably THE most important ground on the truck... basically it is the main neg path from frame to-from the batts as the engine and trans and exhaust are isolated on rubber mounts. Not sure how good a path is provided thru the engine... I recall a,no start issue I helped troubleshoot and come to find out that ground strap had been disconnected/removed, probably during starter work and he could not complete a circuit to power the control circuits in the cab to crank the engine...

 

[JD4044M]

Back Home it was fun the parking was full so I went off road and drove to the fence next to the auction. The guys loved it and was asking if it was to be auction off? The best part was I looked over at my truck and there was someone sitting in it??? Went over to ask why when I saw his Korean War Hat found out he was 83 years old not still all there but was enjoying sitting in a military truck. We talked for a long time. Then someone came up and said so there you are to the old guy and took him away but for a while he was in a different world and I enjoyed seeing him happy!

 

[JD4044M]

Least my Speedometer has smoothed out and on the way home I only had 1-light on the HWY Tire Air Control. Used to work quit and started again then quit once more? Sure glad it runs, drives and stops great cause it would be a bummer having a bunch of engine and transmission problems. I still can drive mine and it starts nice with just a bump of the start button.

Cleaned the connection looked worse then it was. The nut was shinny in the threads and one side. Parts you could not see were free of corrosion but cleaned them better and put it all back on. Not a hard job if you can fold up over the Front Differential and twist your arms. Pulling a Starter could be fun, not bad you just better have a way to support it while bolting and un/bolt the flange on the block!

 

[JD4044M]

Installed the M1078 Generator today I bought a while back off EBay. It works and is charging the Batteries OK. Total Voltage is 28.1 Volts 13.51 VDC and 14.49 VDC to the 12 Volt battery. The 12 volt one needed little more of a charge in the test? After I go for a drive leave them all hooked in over night and see if there is any loss that means anything? The Old one was lower voltage and had a bad bearing too! Just could not hear it over the engine noise. I will save the regulator off it just in case. Nice Original Shock Bushing!! I think I got it this time measured at the batteries. Hoped the Speedo would stay working but dead now. I think I need a new Sensor cause I have checked the other stuff??

 

[JD4044M]

OK Tested the Generator/Alternator today on a long drive in Town. Ran Great and even the Speedometer started working smooth with the proper voltage! After I shut it off I checked the pair of Batteries both 13.32-13.34 so still topped off. Before they would start dropping and I charged them each time I drove. Speedo problem is I did not set the DIP Switches to match the 1995 one. So I was doing 70 in a 35 MPH Zone tagged by a Radar Trailer saying I was doing 35 MPH?? Got home pulled the dash and the new Speedo was switched way different then my old one. So I corrected it. My old one 1995 M1078 AO was 1-10 on-on-off-on-on-off-off-on-off-on I did not write down the new one I changed to this. Also solve my Volt Meter not working the newer ones use 4 wires and my 95 uses 3 wires and I am sure it has to do with the Ground Connection. That is why it did not work. Put the old one back in and it works just a faded inside back plate but reads the right voltage now. Little crap that just bugs you till fixed right!

Other then that I am really loving driving this truck even with a 3800 lb load of water in the bed. I will hate to sell it one day but I think it will be a while. I am still learning the truck and Like what it does on/off road. Pretty smooth too to drive on nice roads with 2 fingers. It just want to go strait down the road I could care less what the MPG are no worst then my 454 Chevy Gas Hog. Need to get the Wife out in it more!

 

[Ronmar]

Installed the M1078 Generator today I bought a while back off EBay. It works and is charging the Batteries OK. Total Voltage is 28.1 Volts 13.51 VDC and 14.49 VDC to the 12 Volt battery. The 12 volt one needed little more of a charge in the test? After I go for a drive leave them all hooked in over night and see if there is any loss that means anything? The Old one was lower voltage and had a bad bearing too! Just could not hear it over the engine noise. I will save the regulator off it just in case. Nice Original Shock Bushing!! I think I got it this time measured at the batteries. Hoped the Speedo would stay working but dead now. I think I need a new Sensor cause I have checked the other stuff??View attachment 838854

What’s that large cable hooked to the alternator ground point?

 

[JD4044M]

I just used it for a better ground adding it going to the frame.

 

[JD4044M]

Had to look inside the Old Generator today just to see if anything looked out of place. I could only get the rear plate of where the smaller coils are. 2 of them looked over heated and were now loose. The rest were OK looking. On the end with the pulley under that plate are many connections. Mine were corroded up but still look like they might work?? Inside the Generator it was real dirty and it also said rebuilt 2005 on it! Glad I changed it out to a clean fresh rebuilt one. They are not water proof and can fill up with dust and dirt!

 

[PNOLEN14]

I hate to be "one of them that can't find an answer" but I need help! LOL

My fire department recently took possession of a 1996 M1078 that was stated to have electrical problems...

Well after further investigation, it turns out that they had the 12v lead on the polarity box swapped to the 24v side which was feeding, of course, 24v to everything. The 12v from the alternator was dead end at the polarity box with the lead going to a negative on the battery which was also wrong (from my understanding). This is a two battery system BTW. We have since changed that lead and got everything back matching another M1978 in the county. NOW, we are getting very high voltage out of the alternator which is about 33v and 14v.

Are there any suggestions as to what I need to be looking for or doing... I'm nearly at a loss after tracking and fixing then this...

ANY AND ALL HELP WOULD BE APPRECIATED! Thanks guys!

 

[coachgeo]

what is your voltage of each battery?

 

[PNOLEN14]

what is your voltage of each battery?

I'm at 17.5 V per battery (2 Battery system).

 

[coachgeo]

I'm at 17.5 V per battery (2 Battery system).

resting voltage?


anyway..... with that output sounds like the miss wiring fubared the voltage regulator. they are expeeeeeeeeeensive. Not sure best route...... cost wise.

 

[Ronmar]

Yep, sounds like the voltage regulator On top of the alternator housing. You can confirm this If you unplug the regulator and start the truck. the alternator should go to no power output Which will confirm the field is not shorted to ground inside the alternator chassis. This alt feeds 28V to one end of the field inside the alternator chassis(from the 28V output terminal), and the regulator connects the other end of the field to ground in pulses to modulate the field current And control the output.

if the alt continues to put out high voltage with the regulator disconnected, the control end of the field is shorted to ground, probably near where the regulator plugs in. I would also inspect the regulator plug and wiring closely for any damage or shorts.

there are two screw terminals on the regulator. The one closest to the pulley is the enable terminal. It gets 24v applied after the engine starts, this tells the regulator to start generating power

the rear terminal(probably labeled F-) samples where the end of the field connects tothe regulator. Engine off you should see 24V via the field winding from the battery. Engine on, on a normal working reg, you should see an AC voltage there if the reg is pulsing that end of the field to ground to regulate field current And output.

on these alts the 24v works like any other alt. The 12v output is controlled by the regulator pulsing SCRs like in a switching power supply.

 

[PNOLEN14]

resting voltage?


anyway..... with that output sounds like the miss wiring fubared the voltage regulator. they are expeeeeeeeeeensive. Not sure best route...... cost wise.

Resting Voltage, not running is 12.5 v. Of course, running at idle 17.5 v.

 

[PNOLEN14]

Yep, sounds like the voltage regulator On top of the alternator housing. You can confirm this If you unplug the regulator and start the truck. the alternator should go to no power output Which will confirm the field is not shorted to ground inside the alternator chassis. This alt feeds 28V to one end of the field inside the alternator chassis(from the 28V output terminal), and the regulator connects the other end of the field to ground in pulses to modulate the field current And control the output.

if the alt continues to put out high voltage with the regulator disconnected, the control end of the field is shorted to ground, probably near where the regulator plugs in. I would also inspect the regulator plug and wiring closely for any damage or shorts.

there are two screw terminals on the regulator. The one closest to the pulley is the enable terminal. It gets 24v applied after the engine starts, this tells the regulator to start generating power

the rear terminal(probably labeled F-) samples where the end of the field connects tothe regulator. Engine off you should see 24V via the field winding from the battery. Engine on, on a normal working reg, you should see an AC voltage there if the reg is pulsing that end of the field to ground to regulate field current And output.

on these alts the 24v works like any other alt. The 12v output is controlled by the regulator pulsing SCRs like in a switching power supply.

Thank you for the info, will def try to troubleshoot more with these ideas.

 

[Ronmar]

The fact it is making the normal 14v output tells me the regulator is at least partially working, driving the SCRs properly to maintain that voltage.