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-   -   Low voltage in drive (http://www.ifsja.org/forums/vb/showthread.php?t=181579)

tensley 12-29-2016 06:01 PM

Low voltage in drive
 
Hey guys. On my 1991 JGW I finally got my power seats, rear defroster, and rear key switch fixed. It was a fusible link, however here is my new problem. While running in park the voltage gauge reads around 14.5-14.7. As soon as I put it in drive (not moving) the needle drops down to around the low 13 or below 13. Put it back in park it jumps right back up. While I'm driving it is around high 13 to low 14 but as soon as I come to a stop sign or red light it drops right back down. My battery is new and I had my alternator checked last night at O'reillys and it checked good. This all started last week after replacing the fusible links. I know they are good because all of the devices are still working with no problems. Is there anything that I still need to check or do? I'm at a loss. Thanks

Joe Guilbeau 12-29-2016 10:54 PM

No problem...
 
Quote:

Originally Posted by tensley
Hey guys. On my 1991 JGW I finally got my power seats, rear defroster, and rear key switch fixed. It was a fusible link, however here is my new problem. While running in park the voltage gauge reads around 14.5-14.7. As soon as I put it in drive (not moving) the needle drops down to around the low 13 or below 13. Put it back in park it jumps right back up. While I'm driving it is around high 13 to low 14 but as soon as I come to a stop sign or red light it drops right back down. My battery is new and I had my alternator checked last night at O'reillys and it checked good. This all started last week after replacing the fusible links. I know they are good because all of the devices are still working with no problems. Is there anything that I still need to check or do? I'm at a loss. Thanks


Your alternator must replenish the amperage given up by the battery when starting, so it's regulator is putting out 14.5-14.7Vdc, this is normal, putting the vehicle in drive provides a load to the engine, and therefore its RPM level drops and therefore the alternator drops output simply due to the fact that the engine spinning the crankshaft pulley at a lower revolution and therefore the belt is spinning slower, and therefore the alternator pulley is spinning slower, and therefore the alternator's output is lower...by design.

Try standing on the brake in drive and press the accelerator to get the rpm's higher, the voltage should go higher.

Make sure you close the garage door and pull right up to it and do the above experiment...

ZackN920 12-29-2016 11:15 PM

Quote:

Originally Posted by Joe Guilbeau
Make sure you close the garage door and pull right up to it and do the above experiment...


WHAT?!:eek: I hope your kidding!

Hey tensely, You still got the stock alt in your Wag? If so, sometime upgrade to a CS-144 alt and you shouldn't have any issues. Previous owner did that to my Wag, and I got great power. Only time mine will dip is if all the lights(including fog's) are on, the AC is on high, and at a stop in gear at low idle.
From what i've read online, the stock alt is barely rated high enough for the stock GW. After a number of years and miles worth of use are on it, it is bound to get weaker with time and then, there ya go....low power:rolleyes:

Joe Guilbeau 12-31-2016 06:21 PM

Quote:

Originally Posted by ZackN920
WHAT?!:eek: I hope your kidding!


OK, you got me, just wondering if anyone actually reads this stuff... don't forget to holler "Watch This!"

serehill 01-01-2017 12:22 AM

it could be more simple.
 
Check your Idle RPM it simly could be too low. Voltage does drop at idle though.


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