No reading on main battery

[SheetmetalD]

Hello everyone. First post so be gentle . I have a no start (as I’m nothing happens) on a 1985 M1009. When my cables are hooked to both batteries I have no voltage reading on front battery. I have 12.31 volts across both batteries. When I unhook cables from both batteries I have a voltage reading of 13.1 on front battery and 12.31 on rear. I can’t get anything to happen with key. Any ideas where to look?

 

[MarcusOReallyus]

Welcome.

Post a pic of your wiring so we can see how it's hooked up, and where you are measuring.

Along with that, disconnect BOTH batteries, and measure from the hot post to the negative post, and tell us what you get for each battery.



By the way, you don't have an 85. You have an 84. The Army didn't want the hassle of dealing with model year changes in their supply chain, so they required them all to be built to 84 specs. When you need parts, you want parts for a 1984 K30 with the J code 6.2 diesel, no matter if your truck was built in 84, 85, or 86.

 

[SheetmetalD]

Welcome.

Post a pic of your wiring so we can see how it's hooked up, and where you are measuring.

Along with that, disconnect BOTH batteries, and measure from the hot post to the negative post, and tell us what you get for each battery.



By the way, you don't have an 85. You have an 84. The Army didn't want the hassle of dealing with model year changes in their supply chain, so they required them all to be built to 84 specs. When you need parts, you want parts for a 1984 K30 with the J code 6.2 diesel, no matter if your truck was built in 84, 85, or 86.

I measured from the ground of front battery to posit

Welcome.

Post a pic of your wiring so we can see how it's hooked up, and where you are measuring.

Along with that, disconnect BOTH batteries, and measure from the hot post to the negative post, and tell us what you get for each battery.



By the way, you don't have an 85. You have an 84. The Army didn't want the hassle of dealing with model year changes in their supply chain, so they required them all to be built to 84 specs. When you need parts, you want parts for a 1984 K30 with the J code 6.2 diesel, no matter if your truck was built in 84, 85, or 86.

I took my reading combined reading with the batteries wired as they should be. I had 12.3ish volts reading from the negative post on front battery to the positive post in the rear battery. I have zero volts reading on the front battery with them wired as they should be. When I unhook both batteries (as in there are no cables hooked to either battery) the front battery reads normal as does the rear battery.

 

[MarcusOReallyus]

I measured from the ground of front battery to posit

A battery does not have a ground. It has a positive and a negative post. Either can be connected to ground, depending on the vehicle's setup. For example, White Freightliners were positive grounded up into at least the '70s or early '80s. Except the ones that came in negative ground, of course. They made them both ways. If you bought a Freightliner, it was a roll of the dice which flavor you got. The history of that is an interesting study in stupidity.

I took my reading combined reading with the batteries wired as they should be. I had 12.3ish volts reading from the negative post on front battery to the positive post in the rear battery. I have zero volts reading on the front battery with them wired as they should be. When I unhook both batteries (as in there are no cables hooked to either battery) the front battery reads normal as does the rear battery.

Okay, it sounds like you have already measured the disconnected batteries, and they are normal. Am I understanding that correctly?

If that's the case, then your wiring is NOT correct. Please post a pic or diagram of the wiring. Don't assume it's correct.

 

[NDT]

I have run into this before on a 1009. The connection between the copper strands in the battery cable and the crimped on battery terminal has degraded. Replace whichever cable is bad.

 

[frank8003]

I have run into this before on a 1009. The connection between the copper strands in the battery cable and the crimped on battery terminal has degraded. Replace whichever cable is bad.

Seen this on many regular cars too..... Inside the cable end attached to battery, they can and do fail after years with the channel lock people under the hood. One can't see the problem and it eats alternators from sometime intermittandt, poor connection.

 

[Skinny]

Positive grounds are for the British and we know how that ended for them...

Is your truck 12 or 24 volts? I don't understand, both batts should read 12 volts and in series makes them 24 volts.

 

[doghead]

And those crafty Euro’s also have been known to refer to it as “earth”. Earth, common, ground, negative…

 

[MarcusOReallyus]

Positive grounds are for the British and we know how that ended for them...

Grounds can be either way. Electrically, there is no real advantage to either. It's a flip of the coin. The Brits changed to match everyone else because it simply makes logistical & marketing sense to have one standard. Much better for the supply chain.

Is your truck 12 or 24 volts? I don't understand, both batts should read 12 volts and in series makes them 24 volts.

Exactly why I asked for pictures. Without seeing how it's wired, we are shooting in the dark.

 

[SheetmetalD]

Being I have downloaded and printed the tech Manuels for the cucvs I am positive the cables are installed correctly. I am also very familiar with positive grounded vehicles as opposed to negative grounded. I guess it’s one’s drive to impress with knowledge one has to point out simple things. Also if the cable had degraded internal it wouldn’t effect the reading across the post if the wire was interrupted.

Positive grounds are for the British and we know how that ended for them...

Is your truck 12 or 24 volts? I don't understand, both batts should read 12 volts and in series makes them 24 volts.

It is still 24 volts on starting circuit. That’s what I don’t understand either. With them wired in series I only get 12.3 volts across the pair. If I read the front battery with them still wired together I get no voltage reading at all. If I read from positive post on front battery to ground on chassis with them wired together I get no voltage reading. Unhook the cables from front battery and it reads normal. Leads me to believe I have ground issues. I be begun the process of tracing all wires.

 

[MarcusOReallyus]

Okay, have fun.

 

[SheetmetalD]

Okay, have fun.

Didn’t mean to get you butt hurt by any means. I mean I get that there are a plethora of people who have no knowledge or mechanical abilities that just start asking questions. I have just never ran into an instance where I wasn’t getting any voltage reading across post of a battery unless it was dead/bad. Surprising when you unhook cables and it reads normal. Maybe my wording could have been better. My apologies and best wishes for you and your family during the holidays Marcus.

 

[antennaclimber]

Have you load tested the batteries?

 

[frank8003]

Have you load tested the batteries?

Make all the ground connections like the day She was built.

 

[Tow4]

Being I have downloaded and printed the tech Manuels for the cucvs I am positive the cables are installed correctly. I am also very familiar with positive grounded vehicles as opposed to negative grounded. I guess it’s one’s drive to impress with knowledge one has to point out simple things. Also if the cable had degraded internal it wouldn’t effect the reading across the post if the wire was interrupted.

It is still 24 volts on starting circuit. That’s what I don’t understand either. With them wired in series I only get 12.3 volts across the pair. If I read the front battery with them still wired together I get no voltage reading at all. If I read from positive post on front battery to ground on chassis with them wired together I get no voltage reading. Unhook the cables from front battery and it reads normal. Leads me to believe I have ground issues. I be begun the process of tracing all wires.

The front battery is dead.

You say above that you are taking the battery reading at the posts. I'm assuming you mean both posts because you say with "the cables" (plural) unhooked it reads normal. If the cables were putting a large enough load on the battery to make the voltage zero, that would mean there was a dead short and there would be smoke and fire if the battery was any good.

 

[Skinny]

Pics or none of this happened

Listen I lose my ____ everytime i read a Land Rover diagram. Dip? Oh you mean low beams

Earth? Yes everything is on Earth except for the Mars rover.

It doesn't help that I got my start on 90's era Toyotas which are known for having meticulously accurate diagrams and naming convention. So when I'm figuring out the fuel pump wires on my buddy's African spec Land Rover 110 that is supposed to have a purple wire that is non-existent I want to either cry or burn it to the ground. Which is not in reference to the the common chassis electrical point