Charging issue!

[CUCV85beast]

For the last couple of weeks my voltmeter has been reading right on the line between yellow and green. Starting a few days ago i found that after its been parked for a few hours or so my batteries are low and it was barely enough to start the truck. With the truck on I'm reading 14 volts at the front battery (which is the drivers side alt) and 11 volts the rear battery (passenger side alt). Figured it made sense that I either have a problem with that battery or a bad alt. I took a reading with my multimeter ground on the negative terminal of the possibly bad battery and the lead on the output of the passengers side alternator, It read the same as the battery 11 volts. My dad says that means there is no problem with any connections in between and the problem is most likely the alternator not putting out enough power.
Went to start this morning and no luck, acting like a dead battery...
I took a reading of the batteries and im getting 12 at the front and still 11 at the rear... almost 24...
I dont wanna go and spend 94 bucks on a new alternator if its possible there is another issue here, any input will be appreciated greatly, thanks

 

[Westech]

well the front battery should be 12 range and the rear battery should read 24 range. sounds like you have a bad alternator or a wire not hooked up/bad conection. First check all battery cables and battery posts to make sure there clean and on correct, then check all alternator conections. Do you have and charging lights on? are the bulbs in the dash for the alternator warring lights good? to get the truck started just switch the batteries around and see if you have enough power to start it and recheck your outputs. If not take the cables off and charge them one at a time till there full and install the cables and go from thre.

 

[Warthog]

The Gen1 and Gen2 bulbs in the instrument cluster have to be operational in order for the alternators to work. They are part of the alternator circuit. Check them first.

I just posted this today.

http://www.steelsoldiers.com/cucv/48145-relay-part-numbers.html

You can take the alternators to the parts store to have them checked. Just them them that they are "isolated grounds". This means that the ground post is isolated from the case. This allows the passenger side alt to take the 14 volts from the drivers side and add its own 14v for a total of 28v.

This isolated ground keeps the Fire Genie in her bottle.....

 

[CUCV85beast]

The Isolated Ground would be that black wire going from the alt to a bolt on my engine right? If thats the case the ONLY my drivers side alt has the isolated ground as there is not one of these on the passengers side.... however my truck has been working fine for the last couple of months like this. I also have NEVER seen my Gen 2 light come on.

Westech- shouldnt each battery read its own 12 volts? doesnt seem right to read 24 volts on the rear battery alone.

I checked the voltage at the starter solenoid and its reading 23.9, when cranked the reading changes too fast to get a solid number but it wasnt going past 22.... I just put in a new starter not too long ago so i doubt thats the problem.

Im gonna switch the batteries around right now and see if that gets it started...

Attached is a diagram of how my batteries are wired

 

[CUCV85beast]

My multimeter is reading 24 volts at the Bus Bar...
doesnt that mean there should be enough power going to the starter??
wtf. this is getting to be a pain in the ass
Im thinking i should take the starter to get checked

 

[Keith_J]

Battery voltage fully charged AND RESTED will be 12.6-12.8. Fresh off the charger, they will be 13.8-14. Dead and rested will be 11.0-12. Voltage is also temperature dependent, higher temps will make for higher voltages.

"Rested" means 12 hours from charging or discharging. If you have 24 volts at the bus bar, you have discharged batteries.

Do both alternator lights come on with key in the ignition? If not, you have a burned out bulb, this will prevent charging as no voltage will get to the alternator to energize the regulator and provide rotor field.

 

[Warthog]

After rereading your post it sounds like you have a bad rear battery, probaly caused by the passenger side alternator not working. Why? it could be a simple as a bad Gen2 bulb in the instrument cluster, a bad Gen2 relay or a bad alternator.

If it is the alternator, you MUST replace it with a "isolated ground" unit. Autozone does not sell one like this. If you don't use this type of alternator, you WILL set the Fire Genie loose under the hood.

The Isolated Ground would be that black wire going from the alt to a bolt on my engine right? If thats the case the ONLY my drivers side alt has the isolated ground as there is not one of these on the passengers side....

You wire diagram looks correct.

The driver side only - has the black ground wire. The red wire output from the driver side runs thru the wiring harness and is connected to the "ground" terminal on the passenger side. This feeds the passenger alternator to create the 24v.

A good alternator should be outputing 14v and a fully charged battery should read 12.6v

With the truck off and the batteries disconnected, check your battery voltage. You may even want to use a carbon arch battery tester.

Reconnect everything and start the truck. Using the front battery ground, check the voltage of the front battery. It should read ~14v. If it is reading less than that the Gen1 is not working.

Still using the front ground terminal, check the battery voltage across both batteries. It should read ~28v. If the Gen1 is working and the voltage is less than 28v, then the Gen2 is not functioning.

With the key on and the engine off, you should see both gen lights come on. If the Gen2 light is not coming on you need to find out why. Most likely the buld is bad or the socket is not making good contact. If the bulb is okay then check the Gen2 relay. It is on the plate mounted to the dash behind where the radio would go.

 

[CUCV85beast]

Thank you for the detail warthog!
Turns out the circuit going to the bulb for gen2 was burned out, so i bridged it with some wire and electrical tape, the light is now functioning fine.
As for the Gen1 and Gen2 relays, I'm reading a little less than 12 volts from both of them. while I'm at it I might as well ask what the one on the left of the steering wheel is with the yellow orange and blue wires on it? the one next to the gen relays is the starter relay am i correct?

How can I tell if my alt has an isolated ground? like i said before the drivers side alt has a black wire going to a bolt on my engine, that same wire is not on the passengers side so by isolated does it mean its in some other location? if so where?... the CUCV faq elaborates on having it on the passenger side but says nothing about driver side side having it too... my truck has been running fine for 2 months so I'm assuming its alright as is... am i wrong?

Gotta get a friend over here to give me a jump to see if this bulb issue has solved it...

 

[mistaken1]

How can I tell if my alt has an isolated ground? like i said before the drivers side alt has a black wire going to a bolt on my engine, that same wire is not on the passengers side so by isolated does it mean its in some other location? if so where?... the CUCV faq elaborates on having it on the passenger side but says nothing about driver side side having it too... my truck has been running fine for 2 months so I'm assuming its alright as is... am i wrong?

The alternator can be an isolated ground alternator (negative lead is not connected to the alternator case) but the drivers side negative output needs to be connected to a bolt on the engine as that is the connection for the negative ground system (the black wire running to a bolt on the engine).

In other words you should be able to swap alternators while maintaining the same connections without starting a fire. If the drivers side was not an isolated ground alternator it would be okay as the negative output and case are connected to the same point electrically but if the passenger side alternator was not an isolated ground the 14V output from the drivers side alternator would ground to the case of the non-isolated passenger side alternator and you would be replacing alternators among other things....

The only way to tell is to isolate the outputs of the alternator and look for continuity to the case.

 

[SmokeyDod]

If you check each battery , front or rear ( I call front the one next to radiator) by just going + to - , they should read 12.5 to 12.9 just as Keith was saying. Even if they are in truck and battery cables hooked up correctly and you check + to - they both should read as above. When you try to check to "24V" battery, you can't just touch probes to back battery. You would on your back battery (next to firewall) put your red (pos) probe to the + side of the back battery and then touck your black (neg) probe to the - side of the front battery. If truck is NOT running, you should get a reading between 25V to 28V . When running you should be getting more volts than above.
REMEMBER when you want to check anything over 20 volts be sure to set your volt checker to the 200V setting., otherwise you could get some confusing readings. I just have one of the cheap multimeter testers which you have to manually switch to volt range. If you have one of the expensive ones, you might not need to do this.

 

[cap-j]

The Gen1 and Gen2 bulbs in the instrument cluster have to operational inorder for the alternators to work. Check them first.
.....

Guys, I am confused about the above, that several of you agree on.

Are you telling me that IF one of these bulbs burn out, the corresponding alternator for the burned out bulb will not charge? Even if nothing is wrong with the alternator????

Is this what is being said???

I am having the same problem and the alternator checked out fine. I have not had time to check further but this thread caught my eye....... so, I thought I'd ask.

Any good info appreciated.
~~~~~~~

As a side note, if it is what is being said and it is correct......... two burned out bulbs could shut down a whole military mission.
Who designed this.... the enemy???

 

[Warthog]

Guys, I am confused about the above, that several of you agree on.

Are you telling me that IF one of these bulbs burn out, the corresponding alternator for the burned out bulb will not charge? Even if nothing is wrong with the alternator????

That is correct. If the bulb burns out, the corresponding alternator will not get energized and will not produce any electricity.

This has been a common design for many years. Can't tell you why but some one spent alot of money at one time...

If you look at the wiring diagram, you can trace the circuit path thru the bulb.

 

[cap-j]

That is correct. If the bulb burns out, the corresponding alternator will not get energized and will not produce any electricity.

This has been a common design for many years. Can't tell you why but some one spent alot of money at one time...

If you look at the wiring diagram, you can trace the circuit path thru the bulb.

Sorry it took me so long to get back here and post my results/findings...... I just forgot..........

First off... I'll just be honest and say.... I thought you had totally lost your mind when you posted this...... and I mean totally!

Long story short..... you hit the nail squarely on the head.

I still can't believe it, but that was the complete answer to the problem......
................. replace 1 burned out bulb.

THANK YOU !!!

IMO, this should be made a STICKY..... cause I may have missed it, but I have never read anything about this on here before.

Thanks again................

 

[pbrstreetgang]

Can someone please post a picture of how to properly hook up the passenger side alternator? I had mine rebuilt today and when I hook it back up, I am getting an arc everytime and everything seems too hot.