Flashing glow light = bad batteries ?

[badger_610889]

Hi all,
I wanted to move my M1043 (M1114 engine and tranny) to work on it today and for the first time it couldn't start, while it cranked and started within a second a couple days ago.

First attempt:
Move the switch to Run, wait for glow plug (wait) light to run off which happens as usual after about 15 sec.
Push to Start, then I hear some repetitive clacks but the engine wouldn't crank.
First I thought it was the gear lever not correctly set so I fiddled it a bit between neutral and park and double checked it's on park.
Tried again a couple times, moving the shifter a bit to make sure its not the tranny believing its not in park, bit always the same result.

I checked the batteries, reading 13.8 and 13.9V and they're dated 2021 so Id expect them to be good.
However, I tried one more time and this time the behavior was different:

After about 4 seconds, the wait light flashes non stop until I turn everything off. It wouldn't crank still, same 'clack clack clack' and I don't like to insisted with that so I cut it after a couple seconds.

The maintenance manual suggests that flashing wait light means unbalanced of defective batteries. Does that sound right per your experience?

I have out a 24V charger on the pair of battery and will see after a few hours. Do you suggest I charge batteries individually with 2 12V chargers to fix some potential balance issue?

the previous owner has setup a 12V loom to power a couple cigarette lighter plugs and USBs in the truck, which I'm not a big fan if anyway. Could that be a cause of battery unbalanced?

Note that nothing was plugged in the truck since it ran a couple days ago.

Thanks for any guidance!

[edit - batteries are from 2021, not 2011]

 

[Mogman]

11 year old batteries are assumed to be good? you need to load test the batteries or at least have a volt meter on them when you try to crank the engine, you have a voltage/current failure somewhere.
It could be a bad connection, start at the batteries and see where the failure is by monitoring the voltage, I would expect the voltage to not drop below 19V or so while trying to crank.
WEAR at least goggles any time you are working around the batteries!

 

[Coug]

agree with mogman. No matter what voltage they read just sitting there, you can't know if they are good or not without a proper tester, which is either applying a heavy load and watching voltage drop, or one of the fancy digital testers that does a capacitance/resistance type check.

plus, sitting at 13.8 and 13.9V is pretty high, so my guess is you have them plugged into a charger to get those readings (it takes a little while to dissipate the surface charge when letting them rest)

it should have a 200 amp generator, so just a 12V outlet wired to the rear battery won't cause an imbalance unless you use it a lot with the truck not running.


"repetitive clacks" sounds like the starter isn't engaging properly, which could be either a bad stater contactor or low voltage.
Low voltage could be either bad batteries or a bad electrical connection.

 

[badger_610889]

Ahah my bad, typo on my phone: the batteries are from 2021 and yes 13.8 volts was reading from the charger/tester.
I'm going back it and will take the time to diagnose that properly...

" WEAR at least goggles any time you are working around the batteries! "
Absolutely! I've seen nasty injuries with batteries, and holes in a sink where my father would have let a battery charge overnight when I was a kid - the hot acid going through it.

 

[Mogman]

Turn the headlights on and then while watching try and start it, if the lights go out OR do not even come on,, then you have a battery/connection issue, if the lights do not go out you have a starter circuit/starter issue. at least that gives you a starting point.

 

[badger_610889]

It's now working and I regret I didn't follow a good procedure to identify what the issue was:
- I took both batteries off and charged them in the garage on separate chargers
- I brushed and retightened all the grounds I could find
- One battery was fully charged after 2 hours the other took almost double but these are different chargers. One is a fully automatic charger/tester and the other one is a good old charger that needs to be setup manually. Maybe I was conservative at 4 amps.

Installed the batteries, it cranked and started in a second as before.
That's great but in the end I'm not sure if it's a charge issue, a defective battery or a ground issue.
I tend to suspect the charge since the voltage regulator is damaged (for those who have seen it in the Slantback M1043A2 introduction thread) but it could still be something else.

Anyway thanks for the support, I'm glad it was fixed the same day and that forced me to take more time checking wirings, grounds and get to know my humvee a bit better !

 

[Coug]

Let it sit for a day or two, then start it, before deciding everything is fixed.
Only a couple hours to fully charge sounds like the batteries are probably good.

Very likely at this point that it was a bad connection somewhere creating high resistance, causing the starter contactor/solenoid to chatter as it just wasn't getting enough power to it.

 

[badger_610889]

I spent a few hours working on the slantback today and made a couple discoveries that explain, at least partially, the issues above.

There was something with the 12V line that the previous owner installed that wasn't right and I couldn't find what. Until I realized there were too many heavy duty cables and connectors on the batteries... I started to follow the extra cables (one was clearly extra because it's red)

Then surprise!



There was another 12V battery in the box under the rear passenger seat!

After removing the extra battery and all the 12V cigarette lighter, USB ports, relays and stuff... the charge is now steady in green zone while it used to be waving between the yellow and green zone.

 

[badger_610889]

Before:


After: