Lower

I've been having trouble with my volt gauge dipping under load. I first noticed that it happened when I stepped on the brakes I'd see just a small dip in the gauge.

I thought this may have been a short or bad ground somewhere, as the trouble went away when I pulled the fuse for the brake lights.

But I hadn't witnessed the radiator fans coming on, and what they do to the gauge. But I came to a point where the car had been running and I saw the gauge dip down into single volts when the fans kicked on, so I was back to thinking it was a charging system problem.

I've replaced the positive battery cable, and coil. Just to rule them out (they were "weak" or old to begin with).

I went to Napa. They tested the battery with a handheld meter and said my 630 cold cranking amp battery showed 430 amps, but otherwise looked good. They figured the alternator was bad, as the battery wasn't getting charged to the proper cca level. They didn't test the alt.

I went to Checkers. They tested both the alt and battery with a handheld meter and while they showed the same results on the battery as Napa (430 cca on a 630 cca battery), since they also checked the alt, they said it was putting out 13.8 volts normally and 14.3 under load. They recommended replacing the battery, as the alt showed the proper volts, but assumed the battery was internally bad due to the low cca level.

I went to Autozone. They wouldn't check my system saying that it was too cold for their readout to work properly. I ordered a new alt while I was there. (Looking back I have no idea why I supported a store that wouldn't check my charging system due to cold weather, I'm an idiot like that sometimes).

I went to Wal-Mart and pulled my battery out. I took it inside and told the returns department what I had been told at Checkers. They sent me back to automotive, and that department said they could only process the return if the battery was bad. They hooked it to their handheld meter, and it showed the same thing as everyone else did; The battery was "good", but not fully charged. It had 12.37 volts on it, but only 430 cca when it should have had 630 cca.
Walmart said this just meant it was undercharged, and while I debated that 430 cca out of 630 cca was not a good battery, they stated the only way they can process the return is if it comes back bad after a load test. 40 minutes later they gave me my old battery back, saying it was good and that they couldn't proceed with the return.

Since then the alt I ordered from Autozone has come in, and I picked up a new serpentine belt since I wanted to be sure to rule out all possible areas. Both have been isntalled, and I've had no change in the symptoms.

I went back to the Walmart I bought the battery from and told them this whole story. I fear that I bored the lady into refunding me the warranteed amount, but I did get my money back.

I have since bought a new battery as well, and had no change in symptoms -although now when the fans come on, the volts dip to about 12, versus about 9 that I was seeing before.

Basically I'm at a loss again. I had thought it was a short or ground problem somewhere in the rear lights area, because when I pulled that fuse the flicker I had when the brake was hit didn't happen any longer. But since the fans are the high load, how could the short or ground be in that line and still have the fans dip?

Grrrrr. Frustrated. Help!
(I know I've posted this update to multiple Fbody type web forums. Please forgive me. I'm so desperate for an answer!)

Thanks!

slopokrodrigez

Sounds to me like you have a bad connection. The 2 most common spots that everyone misses are the grounds at the frame and the engine. You should clean not only the connectors but also the points they connect to. This would account for low voltage under load and low battery current under load. Be sure to clean the connections to the positive battery cluster on the passenger fender also. Always remove and check the battery cables at the battery and don't forget to check the wire at the alternator, although we assume you already did that when you replaced it.

Don't think you have a short for 2 reasons. If they were shorted to ground, you would blow a fuse. If they were shorted to +12V, they would be lit when they weren't supposed to be.

Also when the temperature outside drops, the output of the battery goes down proportionately. Something like every 10 degrees, voltage drops .1V. Hard to remember. The point is, that's when most of the battery, charging problems show up.

I know this sounds stupid but you should put your location up on the left when sign in, and put the year etc. in you signature. It may help some in the future if you have a problem.

Hopefully this will take care of your problem though.

pvkn1ght

dug this up b/c i have a similar problem:

1. my volt guage also dips under load, for example it tick left & right a couple tickmarks with the turn signal on, also dips momentarily when i hit the brakes or when i flip the manual fanswitch.

2. also, the volts read pretty high (sometimes just 2-3 tickmarks under the redzone) when i first start the car, but it decreases to normal levels within a few minutes of driving.

low batt fluid level? (i have a cheapo Sears Diehard, i thought these were zero-maint.)

too weak of a battery? upgrade to better Diehard batt or Optima?

ground connections? slopokrodrigez, where exactly are the ground terminals i should clean?

thanks, Brian

Lower

I don't know. It's been literal MONTHS and I still have this trouble. Your description is word for word what I'm seeing here. I would NOT replace the battery, alternator, or coil -I did and had no change.

I've checked and cleaned every possible ground. No change.
I've disconnected every after market item I've ever installed (head unit, amp, speakers, alarm). No change.

I've all but given up on this.

pvkn1ght

two identical electrical problems

my car doesn't have any aftermarket electronics in it at all and has been doin' this since I got her last Sept.

suggestions anyone? maybe a mod can move this to the advanced forum? heh

12sec97Z28

I am also having the exact same symptoms, and it's not the battery because I have an almost new Optima Red Top battery. Anybody have any suggestions on this?? Battery and alternator have been checked a few times, and pronounced good.

P.S.- Mines a 97 Z28 and I'm in steaming weather in Texas.

RyanS_Z28

go to a dealer instead of autozone and ask them to diagnose a problem at least. even if they tell you something stupid, at least youd get another opinion. it could be a common problem, could be that you have a bad wire somewhere. if all thats happening is stuff is flickering and your getting fresh starts whats the problem?

do you have any aftermarket speakers or subwoofers or amplifiers or anything like that? turning those kinds of things up will cause your lights to flicker and cause dips in the charge.

it doesnt sound like the charging system if you changed the alternator and battery, you should consider something else.

scoobysnax83

mine dips considerably as well when the fans are both turned on via a manual fan switch. It also dips slightly when hitting brakes and turning on the head lights. I believe it is totally normal as it is a huge draw on the system when these things are activated. A real problem would be if the voltage didn't return back to safe levels. If it dips and stays then you have a problem. If it dips and returns to safe levels then well, what can you expect. Just imagine, when you hit the brakes you activate ABS, traction control, 3 brake lights and a series of other systems that countermeasure the reduction in speed. RPM levels need to shoot up to maintain vacuum... plus the alternator needs a millisecond to catch up to the whole process. It can't be instant. The days our cars can read our minds will be a scary day.....

12sec97Z28

If it had always done it, it wouldn't be worrisome, but the fact that it did not do it previously is what worries us. And it gets worse over time. Mine is to the point now that when it does it, sometimes instrument panel lights flicker on and off. I haven't been able to tell which one it is yet, but it's a red light on the left side of the cluster.

scoobysnax83

if its a serious enough problem then it is probably your check gauges light that is flickering.

12sec97Z28

Probably is. Dealership wasn't able to diagnose anything either when I brought it to them. Hope one of you guys find a solution for it. Good luck.

12sec97Z28

I was recently contacted to see if I ever found a solution to this problem. I never actually troubleshot and resolved it, but I do have some insight. The issue goes away in the summer and only really comes back in the cold part of winter. I recently found out that my battery was bad although it did not just completely fail on me, so I have a new one now, and I don't think the issue will be back. I have been through some decently cold weather and not had an issue with it.

As for the hitting the brakes and the guage dipping, you may have corrosion in your tail/brake light terminals. I found out that I had a leak in one of my taillights and water eventually filled one up enough to corrode most of the connections. I have not replaced it yet, but the resistance is so great that when I push my brakes, one brake light will not come on. I plan to replace the taillight harness or the taillight sockets to resolve this issue.

Corrosion on terminals, in sockets, and on ground wire connections seem to be a large reason for this, so cleaning all affected parts would be a good start.