# '97 k1500 strange charging problem



## Thermos017 (Dec 16, 2009)

i have a question about this topic. i doubt any of you have ever ran into this problem, but i cant track it down. It is a 1997 k1500. the dual battery setup was wired in by yours truly. i have a 105/113A alternator running through a 120A battery isolator. the primary battery usually charges at around 13.5v while the aux. battery runs about 14.5-15v. 

this system worked flawlessly for over a year, then one day the gage fuse blew and the main battery died (not while plowing). after replacing the fuse it charged fine for about 3 weeks, then the fuse blew again. after disconnecting several items and continuing to blow fuses i decided to quit. i hooked everything back up, disconnected my jumper cables, and tried one last time for giggles. the truck fired right up, and hasn't blown a fuse since. now the problem is, the alternator only charges when and after the truck is put in reverse. after putting it in reverse it continues to charge indefinitely until the truck is shut off. after starting it has to be put immediately into reverse again, or the alternator won't charge. 

i have tried a new alternator (because napa's tester broke) with the same results. i have checked voltage at the signal wire and it seems to be getting juice before the truck is shifted into reverse, so why wouldn't it charge? i have also tested the isolator, and as far as i can see it is operating properly. also, before you ask, i checked the voltage at the main and aux battery, as well as the back of the alternator. the alt simply isn't operating at all until the truck shifts into reverse. if i quickly shift past reverse into drive it doesn't start charging. is there any tie at all in the wiring between the neutral safety/backup switch and the igniter signal wire to the alternator? or am i going to be tearing the dash out and tracing wires for the next week? the only simple test i haven't tried yet is a jumper directly from the battery to the igniter signal post of the alternator. if/when i do that test i'll post the results here.

i realize this is an oddball issue, i'm just hoping someone has ran into it before and can give me a quick answer without having to dive into the harness. also FYI, this issue seems to have absolutely nothing to do with the plow system at all. it did coincidentally happen right after my "slick stick" failed. that is repaired and operating properly now so i'm confident they are unrelated issues. just lousy luck


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## Thermos017 (Dec 16, 2009)

*97 k1500 silverado charging problem*



B&B;908990 said:


> That's a very very odd one indeed and not something that may be simple to diagnose via the internet. But a couple things to try and then check back here....
> 
> Pull the turn/BU lamp fuse and see if it still begins to change after the shifter is placed in reverse.
> wow, don't know why i didn't think to try that. will report the results in the a.m.
> ...


thanks for the info thus far B&B


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## B&B (Nov 4, 2006)

For your jumper wire to the alternator you can add an inline 1156 or 3156 light bulb. It provides enough resistance to safely do the job. But I think you'll find it charges just fine with the jumper on so that won't really tell you much.

Let us know what you come up with on the details...


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## Thermos017 (Dec 16, 2009)

*It's alive!!!*

i believe i have tracked down the problem to the gauge cluster. i removed it to check the connection and noticed that you can easily move the assembly left and right about a 1/4 inch. if the unit is shifted too far one way or the other, it will blow the guage fuse. also, i believe the offset plug was allowing the shifter position light for reverse to send the signal to the alternator to start charging. after carefully aligning the pins in the connector attatched to the dash with the cluster, and ensuring the screws were as tight as possible without stripping them, the charging seems to be working just fine now.

I've also performed some of the upgrade ideas for the charging system that i read about on the dual battery setup thread. i'll be posting pics of my setup on that forum after work tonight.


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## B&B (Nov 4, 2006)

The cluster and/or its connection is what I was leading up to with having you pull the B/U lamp fuse. The exciter wire goes from the alternator DIRECTLY to the instrument cluster, through the connector of course and to the charge indicator...but would you like to take a guess as to what else is also on the circuit that feeds 12V to gauge fuse? 

Yep, the same circuit that feeds the B/U lamp fuse.


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