Belt won't stay on problem

[vgodenwa]

Belt won't stay on problem - pics added

Guys, I have a M1028 that someone added A/C to and didn't do the best job on the pulley setup. The A/C is on the driver's side, and the second alternator is way over on the driver's side. I'm having trouble keeping a belt on the second alternator due to poor adjustment range (long story, can't get it very tight) and possibly some alignment issues.

I have searched, I promise, and I can't find a case of someone who still has 24V setup, 2 batteries, and simply runs one alternator. The obvious reason may be that it won't work, which is what I'm asking. The truck also has a 12V fuel pump added. Will both batteries charge from one alternator since it does it on modern trucks? Or does the 24V setup have to have 2 alternators? Can one alternator handle the A/C and the electric pump?

Please don't flame me - I'm sure a guru could figure this from the TM's, but I'm not bright enough to figure it out, and one of you can probably tell me off the top of his head.

Thanks in advance.
Von

 

[nf6x]

The original alternators in the CUCV are 12V units, so a single one of them cannot charge both batteries in a 24V system. I haven't had hands on a CUCV ambulance before, but if I was in your shoes, my first impulse would be to look for the brackets and other hardware that the ambulances use to mount the AC compressor, and then to fix the belt setup using those parts.

 

[vgodenwa]

That is a great idea.
When you say the single can't do it, can you explain?
I'm under the impression that if you have multiple batteries, the lower charged battery (because it doesn't have an alternator) will pull down the good battery, which will be recharged by its alternator. Not an ideal situation, but they both stay charged???

 

[nf6x]

In the CUCV, one 12V alternator charges the lower 12V battery, and the other 12V alternator charges the upper 12V battery. This is distinctly different than in most other military vehicles, where a single 24V alternator charges both batteries at the same time as if they were a single 24V battery.

 

[nf6x]

I should add that in the CUCV, if one alternator isn't working, its associated battery will not get charged at all. The two batteries are charged independently by the two alternators.

 

[vgodenwa]

OK then, I guess it has to be fixed.
Thanks so much.
Von

 

[cpf240]

I should add that in the CUCV, if one alternator isn't working, its associated battery will not get charged at all. The two batteries are charged independently by the two alternators.

Actually, this has been puzzling me for some time.

Each battery is, on its own, only 12v. Since Gen 2 outputs 24v to the 24v buss, which is made up of both batteries, I'd think that Gen 2 charges both batteries.

So...

While Gen 1 charges only the front battery, it also provides the ground reference voltage for Gen 2. Gen 2 does not "only" charge the rear battery, it charges both batteries in their series 24v configuration.

Gen 2 can only produce 24V if its ground reference is +12v, which it gets from Gen 1, and - I suppose - the front battery - as long as that battery holds at 12v.

So, if Gen 1 stops working, and the front battery doesn't have the capacity, won't Gen 2 be unable to keep functioning properly? I would think you could go for a little while, but wouldn't there be some form of performance curve where at some point the system just collapses?

 

[amphi]

If either Gen stops working the other one will continue to charge it's respective battery if it is in need of a charge. Each Gen senses the charge level (voltage) of it's own battery, thru the small red wire, and responds accordingly. At times both batteries are charging simultaneously thru both Gen's in series at 24v.

This post contains images of an article published in Military Vehicles Magazine August 2010 issue #141:
http://www.steelsoldiers.com/cucv/45571-can-someone-explain-isolated-ground-3.html#post944284

The article explains in detail how this works.

Color drawings and videos of the actual tests can be seen here:
CUCV

 

[nf6x]

Actually, this has been puzzling me for some time.

Each battery is, on its own, only 12v. Since Gen 2 outputs 24v to the 24v buss, which is made up of both batteries, I'd think that Gen 2 charges both batteries.

Gen 2 is a 12V generator, with its positive side connected to the 24V bus, and its negative side connected to the 12V bus at the junction between the batteries. So, it is not outputting 24V with respect to the chassis ground; it's outputting another 12V above the 12V bus.

If the lower battery voltage droops because it's not getting charged, then the 12V bus droops, and Gen 2 follows it down. Gen 2 can't put 24V onto the 24V bus unless the 12V bus is at its proper voltage. So, that's why one of the alternators can't charge both batteries.

Does that help?


BTW, I'm calling the buses "12V" and "24V" as is the convention, but while the vehicle is running the actual voltages are closer to 14V and 28V, respectively.

 

[vgodenwa]

I'm all confused.
I'm so non-mechanical that I've had a mechanic working on it.
I thought because it was 24V that the batteries were wired parallel not series.

 

[Warthog]

The CUCV is a totally different animal.

Just any mechanic will also be confused and will want to rip all the wiring out and rewire so he understands it.

DO NOT let him do it.

The CUCV wiring works very well as it is dssigned.

When soeone added the A/C, they didn't understand it and screwed something up.

Many people are running two alternators and an A/C compressor. There are even kits out there.

Without seeing pictures of how yours is setup, we are all just guessing.

 

[Warthog]

You can not use a single 24v alternator on the CUCVs without using some type of voltage inverter. The M1010s do this with the Duvac system.

Yes one 24v alternator will charge two 12v batteries in series.

The problem arises when you are drawing 12v for just one of the batteries as most of the truck is 12v. This causes a load imbalance and the alternator will sense a low voltage condition and up the amperage.

This will charge the "low" battery and cook the second one as it isn't discharge and is now being over charged.

Is this a clear as mud?

Amphi did a great study of this and tried to explain it in laymans terms.

 

[txmytx_catahoula]

Not sure if this helps anything or just stirs up more mud. After reading through section II of the TM-20, chapter 1-10, on page 1-3, is it possible the OP has one of the m1028's that's incorporated the m1010's changing system? If so the A/C could be original and the brackets are FUBAR. Just a thought.

 

[nf6x]

I'm all confused.
I'm so non-mechanical that I've had a mechanic working on it.
I thought because it was 24V that the batteries were wired parallel not series.

The batteries are wired in series to make 24V. Voltages add when they are connected in series, and currents add when they are connected in parallel.

In case you're not clear on the difference between voltage and current, I'll make a garden hose analogy: Voltage is the electrical equivalent to pressure, which is how hard the water pushes on your thumb when you put it over the end of the garden hose. Current is the electrical equivalent to flow rate, which is how quickly the water comes out the end of the hose.

Voltage and current are related to each other, just like water pressure and water flow rate are related to each other. Now, if you want to get even more confused, then we can start talking about energy and power... two more things that are very commonly misunderstood!

 

[vgodenwa]

OK, here we go:

Here is the compressor:
http://i148.photobucket.com/albums/s16/vgodenwa/DSC06169.jpg

This is the jerry-rigged bracket that won't adjust because it is just a radius instead of actually lengthening the belt:
http://i148.photobucket.com/albums/s16/vgodenwa/DSC06158.jpg

Here are the brackets from behind:
http://i148.photobucket.com/albums/s16/vgodenwa/DSC06162.jpg

Here is an overview:
http://i148.photobucket.com/albums/s16/vgodenwa/DSC06157.jpg

Batteries:
http://i148.photobucket.com/albums/s16/vgodenwa/DSC06168.jpg

Overview from passenger side:
http://i148.photobucket.com/albums/s16/vgodenwa/DSC06166.jpg

 

[wayne pick]

hea vgodenwa, I may have a solution to your belt problem. the radius on the adjustment bracket is causing a pinch point between the top of the alt and the bracket, you already know this. I think a bracket with a tighter radius, more like a half circle will resolve the problem with the bracket making contact with the alternator. search junk yards or show the junk yard guy what you need. Summit or Jegs may have custom brackets also. The alignment on the alt looks like it needs to go back twards the firewall a little. This can be done by grinding some materal off the back of the pivot point casting- where the bolt goes through the bottom of the alt, and making up the distance with flat washers on the front side. Use a strait edge of some kind to align the alt pulley to whatever pulley the belt is driven from. You may also consider using a ideler pulley to help with adjustment- new style GM for serpentine belts used the same way on the back side of the belt. It looks like a hockey puck, there all the same fom s10 to c65. And as said above, don' alter the electrical sys on your truck and don't let enexperenced mechanics learn how to work on it either. New adj bracket in black marker in photo. Good luck. WCP