Volt meter wrong and batteries die

[m-35tom]

Now I know that sounds simple but, 2006 A1R 7000 miles total. 4 new batteries charged and installed. 24 v meter on dash shows 24, 12 v meter on dash shows right at the yellow/green and constantly moves up and down while meter on low set of batteries shows constant 14 volt. Meter on high set shows constant 14 volt. This is at idle and alt lights show green.
Further it sat for 2 days and batteries went down to 11 volts on all and would not even try to crank.
Any ideas except that the 12 v meter must be bad?
Thanks, Tom

 

[Suprman]

I would check the load battery box behind the cab.

 

[Ronmar]

Well a bad 12V meter shouldn't have drained the batts. Meter performance could be a case of garbage in-garbage out. Have you connected a multimeter at the panel meter? It sounds as if y0u have a wiring issue somewhere or a failed component such as a polarity box or even an alternator, causing a discharge.

With everything turned off(like when the batts discharged) and with a fully charged set, you could put a current meter in line/series at the batteries to measure the drain, then start disconnecting circuitry downstream until you remove/find the source of the drain.

 

[m-35tom]

Right but a meter on the batteries shows correct charging voltage. I know that doesn't account for the drain, alt was cold. when I got the truck it had sat for 1 year and the batteries had frozen but 3 of them recovered. I replaced all 4 just because. At first 12 volt meter on dash worked correctly.

 

[m-35tom]

I would check the load battery box behind the cab.

In what way?

 

[Ronmar]

Right but a meter on the batteries shows correct charging voltage. I know that doesn't account for the drain, alt was cold. when I got the truck it had sat for 1 year and the batteries had frozen but 3 of them recovered. I replaced all 4 just because. At first 12 volt meter on dash worked correctly.

Yea, I got that the alt was charging ok at the batts, measuring good voltage there and bad at the panel meter = bad meter or bad wiring. What I was getting at was depending on how yours is wired, the alt could be responsible for the drain.

does yours have a manual disconnect switch and was it turned off when the batts discharged? If it was left on, there is a 24V sense line from the manual sw outlet to the polarity protection box. On the A1 schematic I have it looks like they put some load and voltage sensing into that device to monitor current flow, alternator load and it can output to control the disconnect relays to unload the alternator and batts during an overload. Not sure if they did this same functionality in the A1R, but if they did, A problem there could be causing the discharge with the manual disconnect left on.

a connection problem in the polarity protection box could also cause your volt gauge readings...

 

[Suprman]

Under the box to the right of the batt box, where the disconnect relay is, should be a manual disconnect switch. Reach under the box it turns.

 

[simp5782]

What mine says. Probably a clue that there is a drain

 

[m-35tom]

Under the box to the right of the batt box, where the disconnect relay is, should be a manual disconnect switch. Reach under the box it turns.

yes, I know that.

 

[m-35tom]

OK, with disconnect switch on batt drain is 40 ma, with switch off drain is 5 ma. batts should last a year at that draw! maybe just a troll under the truck?

 

[coachgeo]

OK, with disconnect switch on batt drain is 40 ma, with switch off drain is 5 ma. batts should last a year at that draw! maybe just a troll under the truck?

maybe a plug in or solar battery tender is in the cards at some point to offset the draw?

 

[m-35tom]

that's the thing, what draw? and why did new batteries go flat in a couple of days?

 

[Ronmar]

Thats not much draw. A corroded connector or module could perhaps provide a current path and cause more drain when wet?

Looking at the A1 schematic the troop heater wiring bypasses the cutoff switch also so a circuit being created there could also drain the batteries.

Or lastly did it accidentally get left on?

 

[m-35tom]

Ron, Thanks, no I don't see how anything could have been on. Do the wires for 12 volt meter go directly somewhere I could access they without taking dash out?
Tom

 

[Ronmar]

Well of course they go somewhere but since the meter is in question the best place is at the meter. The dash isn't so bad once you tilt and extend the steering column.

cb77 and cb83 feed the 12/24V meter switch...

 

[m-35tom]

OK, I want to take the entire dash out anyway to clean and to remove brake treadle valve, not captive nuts! Need access to back side of front as it got hit and very bent up. This 18 ga steel is hard to work with!
Thanks

 

[Suprman]

I usually pull the steering wheel if I need to get deep into dash work.

 

[m-35tom]

Since I want to remove the entire instrument panel, are the gauge plugs numbered? or only go to one gauge? I have the manual but have been unable to install it.

 

[Suprman]

The wire harness has numbering on each wire leading to a plug. Write down each one before you disconnect. The manual should have a schematic showing where it all goes but it’s easier if you keep track of the connections yourself. I take pics with my cell camera as I am taking stuff apart too.

 

[m-35tom]

OK thanks for the suggestions. Maybe I didn't have a battery problem, here is what happens. New batteries fully charged, sit for 2 days with relay off. Batt voltage is 24 volts. Turn on under dash switch and then dash power switch everything seems fine. Push start and clunk, nothing. If hold start switch it cycles. I now have a '94 A0 and a '06 A1R truck that do the same thing!