Front battery charging to 12.5

[Cmwalton]

So I replaced gen 1 alternator because it was only charging to 10volts while rear was charging to 14 I had gen 1 rebuilt and right after putting it in it was charging to 14 like it should and I was getting 28v across both battery’s now a day later front battery is only charging to 12.5 and back is charging to 15 and I’m getting 27v across both battery’s what could be the cause for this? All battery cables and grounds are clean and tight also

update after driving it more the front battery is now down to 10volts like the gen 1 went bad again also my gen2 light comes on and my gen 1 light doesn’t and but I’ve made sure bulb and socket work in gen 1 but light still doesn’t illuminate

 

[Der Dicke]

Look at my problem and the advice from Tow4:

Oh no. Another one with a problem with the 12V alternator 1 (driverside)

Hello, please don't shoot me, but I have a problem with the alternator 1 (driver side). I find a lot of good threads to check, but I could not solve my problem. Possibly overlooked. Alternator 2 is charging, #1 is not. Before the engine was changed (timingchain crack), it works. The Gen1 lamp...

www.steelsoldiers.com

 

[Barrman]

12.6 volts is what the battery should be at with the truck off. If you don't have that, you need to charge the battery before you do anything else. You should also load test the battery.

How long are you cranking the engine to get it to start? Something is pulling voltage from your battery. Even with the glow plugs on, a normal battery in good shape will only get down to 10.8 or 10.9 volts during the glow cycles. Then it will bounce back to at least 12.3 with the engine off.

A normal 6.2 in healthy condition with a 24 volt starter should fire up hot or cold in less then a second after you start to crank the engine over. Anything over 3 seconds means something is wrong. Bad batteries, bad starter wiring, bad starter motor, bad glow plugs, bad glow plug relay, dirty fuel filter, bad injection pump, etc....

I daily drove my M1009 when I first got it with a bad alternator 1 for 2 weeks. I averaged 15 glow plug cycles and starts without the battery being charged before battery voltage would be below 11.5 volts. Then I would charge for an hour and be good for another 15 starts. Something is wrong on your truck if you go from 12.5 down to 10.? in just one drive without the lights, heater and wipers on.

 

[Cmwalton]

12.6 volts is what the battery should be at with the truck off. If you don't have that, you need to charge the battery before you do anything else. You should also load test the battery.

How long are you cranking the engine to get it to start? Something is pulling voltage from your battery. Even with the glow plugs on, a normal battery in good shape will only get down to 10.8 or 10.9 volts during the glow cycles. Then it will bounce back to at least 12.3 with the engine off.

A normal 6.2 in healthy condition with a 24 volt starter should fire up hot or cold in less then a second after you start to crank the engine over. Anything over 3 seconds means something is wrong. Bad batteries, bad starter wiring, bad starter motor, bad glow plugs, bad glow plug relay, dirty fuel filter, bad injection pump, etc....

I daily drove my M1009 when I first got it with a bad alternator 1 for 2 weeks. I averaged 15 glow plug cycles and starts without the battery being charged before battery voltage would be below 11.5 volts. Then I would charge for an hour and be good for another 15 starts. Something is wrong on your truck if you go from 12.5 down to 10.? in just one drive without the lights, heater and wipers on.

sorry, I should have been a little more specific with truck running it was 14.5 after having alternator rebuilt then I put about 30 miles and checked it again and it was down to 12.5 while running then after another 15 miles it was down to 10 volts while running, battery’s are from 2019 Napa commercial battery’s but I will have them tested to make sure 1 or both didn’t go bad

 

[Barrman]

Was the heater on high, lights on and wipers flapping? Even then it shouldn't drain the battery that fast. Check your batteries and have them load tested. Then go from there. You might have a bad alternator, but something else is going on as well.

 

[Cmwalton]

Was the heater on high, lights on and wipers flapping? Even then it shouldn't drain the battery that fast. Check your batteries and have them load tested. Then go from there. You might have a bad alternator, but something else is going on as well.

no they were not on for those voltages but when I would turn them all on the front battery would drop to 9volts, I will charge battery’s up and have them load tested thanks

 

[dougco1]

no they were not on for those voltages but when I would turn them all on the front battery would drop to 9volts, I will charge battery’s up and have them load tested thanks

Sounds like one or more of the battery cells are shorted. The battery load test will tell all.

 

[Cmwalton]

Had them load tested yesterday they both tested 900 out of 950 cca so he told me they are still good guess it’s time to check gen 1 again after having it rebuilt 2 weeks ago, I’m also only getting like 3 volts with key turned to on at the white exciter wire and it’s spliced into this pink wire under steering column is that correct?

 

[Cmwalton]

Look at my problem and the advice from Tow4:

Oh no. Another one with a problem with the 12V alternator 1 (driverside)

Hello, please don't shoot me, but I have a problem with the alternator 1 (driver side). I find a lot of good threads to check, but I could not solve my problem. Possibly overlooked. Alternator 2 is charging, #1 is not. Before the engine was changed (timingchain crack), it works. The Gen1 lamp...

www.steelsoldiers.com

unfortunately I think my alternator is hooked up correct and I’m still having problems I may try using jumper wires to see if that helps solve my problem

 

[Curtisje]

This info may help, may not.

GEN 2 Exciter Voltage M1009 SOLVED!

OK I have been troubleshooting this all week. The information on this site and received from members is amazing. But one thing I had to figure out on my own. Maybe I missed it on here, so I’m sharing it now. the GEN 2 exciter voltage was reading .2 and GEN 2 was not working. I traced all the...

www.steelsoldiers.com

 

[Cmwalton]

Look at my problem and the advice from Tow4:

Oh no. Another one with a problem with the 12V alternator 1 (driverside)

Hello, please don't shoot me, but I have a problem with the alternator 1 (driver side). I find a lot of good threads to check, but I could not solve my problem. Possibly overlooked. Alternator 2 is charging, #1 is not. Before the engine was changed (timingchain crack), it works. The Gen1 lamp...

www.steelsoldiers.com

unfortunately I think my alternator is hooked up correct and I’m still having problems I may try using jumper wires to see if that helps solve my problem

This info may help, may not.

GEN 2 Exciter Voltage M1009 SOLVED!

OK I have been troubleshooting this all week. The information on this site and received from members is amazing. But one thing I had to figure out on my own. Maybe I missed it on here, so I’m sharing it now. the GEN 2 exciter voltage was reading .2 and GEN 2 was not working. I traced all the...

www.steelsoldiers.com

Thanks for the suggestion, I can try cleaning circuit board again but I wiped it off with my finger because there was a little bit of build up on it and still no luck