Battery voltage gauge dips
Thread Starter
Staging Lane
Joined: May 2014
Posts: 58
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Battery voltage gauge dips I was having all sorts of issues with my battery gauge wildly jumping around earlier this year. I think the issue ended up being a combination of an aging alternator and water in my tail light. I ended up replacing the alternator with a truck alternator and drilling drain holes in my tail light (see previous thread I started). That took care of the rough idling and wild voltage needle swings from 10 to 15 volts that I was seeing. However, I still notice my battery gauge dips whenever I press the brakes or have a turn indicator on. It holds steady at 14 volts when running. When I press the brake, I see a momentary dip down to around 13 volts but it immediately goes back to 14. When I release the brake, the needle doesn't move. I notice the same thing if my indicator is on in either direction, the needle does a momentary dip with each flash though not as pronounced. The car seems to be otherwise running fine when this is happening.
Could this be a ground issue somewhere? Or is this just normal behavior? I don't remember seeing the needle twitch prior to when my issues with the alternator and water in tail light started. Thanks.
Could this be a ground issue somewhere? Or is this just normal behavior? I don't remember seeing the needle twitch prior to when my issues with the alternator and water in tail light started. Thanks.
Thread Starter
Staging Lane
Joined: May 2014
Posts: 58
Likes: 0
So I tried doing parts of the big 3 to see if that would help solve the problem, but it did not. I ran a 4 gauge from the alternator to the battery and while I was down there I ran a second 4 gauge from the relay box to the battery. I zip tied them to the existing cables that run along the back of the fan shroud. I noticed there is another short positive jumper right under the main battery post on the relay box that looks fairly aged but left it as is for now.
I ran a 4 gauge ground from the block to the chassis (no longer have rear alternator bracket so used mounting hole for that to attach to block and attached other end to ground screw near driver side strut tower as seen in pics). I was trying to find the factory ground strap that connects near the alternator to the chassis and after looking for it for 10 minutes I realized it was in front of my eyes the whole time but way smaller than what I was picturing in my head. I tagged it in the photo. I already had a ground jumper from battery to passenger side strut tower area but I replaced it anyways.
After all this, the needle still momentarily dips any time I apply brakes or turn on headlights or defroster etc. I uploaded a video that shows what I am seeing any time an electrical load is applied. Dips for a split second and then goes back to normal. I am starting to think it's related to the alternator itself unless anyone else has some ideas to try.....over all the car is running fine but I'm concerned that could change. The alternator was a used one from a 2003 Hummer with approx. 40k miles on it, been in the car for about 9 months.
I ran a 4 gauge ground from the block to the chassis (no longer have rear alternator bracket so used mounting hole for that to attach to block and attached other end to ground screw near driver side strut tower as seen in pics). I was trying to find the factory ground strap that connects near the alternator to the chassis and after looking for it for 10 minutes I realized it was in front of my eyes the whole time but way smaller than what I was picturing in my head. I tagged it in the photo. I already had a ground jumper from battery to passenger side strut tower area but I replaced it anyways.
After all this, the needle still momentarily dips any time I apply brakes or turn on headlights or defroster etc. I uploaded a video that shows what I am seeing any time an electrical load is applied. Dips for a split second and then goes back to normal. I am starting to think it's related to the alternator itself unless anyone else has some ideas to try.....over all the car is running fine but I'm concerned that could change. The alternator was a used one from a 2003 Hummer with approx. 40k miles on it, been in the car for about 9 months.
Thread Starter
Staging Lane
Joined: May 2014
Posts: 58
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I noticed the battery gauge would swing even more wildly when I turned up my new stereo (see youtube link below). I hooked up a fast update DMM to the battery while the car was running and stereo/headlights/wipers were at max. The voltage would hover around 14.78 volts but would show dips as low as 12.82 volts whenever a bass note hit. The stereo runs off a single 80A fused D-class Alpine PDX v9 amp rated for 900 watts rms. The amp is over 80% efficient so I wouldn't expect the power draw to affect the battery gauge as much as it is considering I've done the big 3-4 and have a 145A truck alternator installed. With the car off the battery voltage is 12.26 volts which I think is good (fairly new battery).
The stereo effect on the battery gauge is just the latest thing I've noticed. Even with the stereo off and all other electrical off, I still notice higher than expected movement of the needle when say just the turn indicator is on. I am starting to suspect the alternator. It can handle high current loads (all electrical on in car and voltage steady at 14.75 volts), but it doesn't seem to keep up with the transient changes in load very well. I'm not even sure if alternators are supposed to deal with transient changes or if a stiffening cap is required. I just wanted to keep updating this thread until/if I find a solution. I may post on the stereo forum to see what others might have done. Thanks.
https://www.youtube.com/watch?v=wdfI...ature=youtu.be
The stereo effect on the battery gauge is just the latest thing I've noticed. Even with the stereo off and all other electrical off, I still notice higher than expected movement of the needle when say just the turn indicator is on. I am starting to suspect the alternator. It can handle high current loads (all electrical on in car and voltage steady at 14.75 volts), but it doesn't seem to keep up with the transient changes in load very well. I'm not even sure if alternators are supposed to deal with transient changes or if a stiffening cap is required. I just wanted to keep updating this thread until/if I find a solution. I may post on the stereo forum to see what others might have done. Thanks.
https://www.youtube.com/watch?v=wdfI...ature=youtu.be
