Paintball Guns and Gear forums banner

1 - 14 of 14 Posts

·
PbF Supporter
Joined
·
4,738 Posts
Discussion Starter #1
So when I turn the Heater/AC fan on in my truck (1994 GMC Jimmy) my lights dim A LOT, I mean it’s extremely noticeable. I thought nothing of this when I first got it, I though "hey its old, whatever" but then I noticed the battery gauge is no joke RIGHT under the red line as if its too charged when the car is running, but when just the ignition is on, its right over the halfway mark where it should be.

But see the thing is, my battery has one of those green lights on it that says it’s OK, and that’s on. AND when I turn on my 2 sets of Off-Road lights on, the gauge drops down to the half way mark again while the car is running.

I'm thinking maybe the alternator is bad, as in it’s over charging the battery?

Any ideas?
:?
 

·
see you at the 50
Joined
·
446 Posts
go hit up advance auto or vatozone and have em run their little arbst tester on your ride, it's free. any voltage problems or power probs while the car is running is generally a failing alternator... but at either store they will be able to check the alternator output from the voltage regulator, amps, and whether or not the diodes are good, and they will check the batt. and about the green indicator on the delco batteries, it gets stuck green half the time.
 

·
Imperator
Joined
·
19,071 Posts
Sounds like the alternator is starting to go bad or the battery isn't holding a charge anymore. Pretty common problem in older/higher mileage vehicles, especially if running a high output stereo or high drain off-road lighting. When I put off road lights, a GPS, and built in radar detector in my truck I changed the alternator to higher amp model and changed the battery to an Optima yellow top. I've had my high beams on, two HID off-road lights on, the radio blasting, the air on, and my GPS on all with no problems.
 

·
PbF Supporter
Joined
·
4,738 Posts
Discussion Starter #6
doomsday said:
Sounds like the alternator is starting to go bad or the battery isn't holding a charge anymore. Pretty common problem in older/higher mileage vehicles, especially if running a high output stereo or high drain off-road lighting. When I put off road lights, a GPS, and built in radar detector in my truck I changed the alternator to higher amp model and changed the battery to an Optima yellow top. I've had my high beams on, two HID off-road lights on, the radio blasting, the air on, and my GPS on all with no problems.
How much did both those together cost you?
 

·
Registered
Joined
·
363 Posts
The green dot means that the battery is high enough to test, not that it is ok. A simple test can be performed at any auto parts store. Just remember the test we perform outside shows if it is charging or not. Wiring can be a major role. Just b/c it isnt charging doesnt mean that the alternator has to be bad. A short, bad ground, or corroded battery terminals can also make this kind of thing happen. Doomsday's Idea is great it you got the cash. Optima batteries start at about $159 usually and high amp alternators can cost alot depending on what amp and style. You probably have a 105 amp on your jimmy already a higher amp might not be nessesary. Have it tested, this will tell you were to start. If they say the alternator is bad take it off and have them test it in there store on there bench tester. If it tests bad then you know where your problem is, if not check you wires.
 

·
PbF Supporter
Joined
·
4,738 Posts
Discussion Starter #8
Alright well depending on if I have to do something with my girlfriend, I'm planning on taking it over to the AutoZone and having them take a look at it. So tomorrow I might be back with what it’s been diagnosed with.
 

·
Registered
Joined
·
4,618 Posts
my lights dim a lot when i turn on my a/c or heater also, but they go right back up.. i think it's just the initial drain that kinda shocks it quick. idk about your battery guage though, probably something like what one of the other guys are tlaking about.. i dont have a battery guage so idk what mine would look like..
 

·
PbF Supporter
Joined
·
4,738 Posts
Discussion Starter #10
HuNtS said:
my lights dim a lot when i turn on my a/c or heater also, but they go right back up.. i think it's just the initial drain that kinda shocks it quick. idk about your battery guage though, probably something like what one of the other guys are tlaking about.. i dont have a battery guage so idk what mine would look like..
Yeah mine come back up A LITTLE when I turn it on, I should have mentioned that.

What kind of car do you have?


EDIT: NVM, I saw your sig.
 

·
Registered
Joined
·
4,618 Posts
lol yeah... but i'm also running a 1700 watt sound system, and off road lighting, and about a half a million other things connected to my battery, so it's usually quite drained the way it is.. i'd guess probably a charging issue
 

·
Imperator
Joined
·
19,071 Posts
CoolHipJim56 said:
How much did both those together cost you?
It cost me about $300, but I got the parts cheap, if you go by street cost it would have been around $400-$450 plus the installation cost.

Anyway, yea, take it over there and have them look at it. Like darkdragon said, it could be corrosion or bad wiring too. It's best to check everything out before you start dropping a lot of cash.
 

·
Registered
Joined
·
3,172 Posts
Sounds to me like the regulator inside your alternator is bad. Lights dimming because of the heater is no big deal because the heater is one of the largest electrical loads in the car (normally). You cant just replace the regulator usually so it looks like you'll need a new alternator. Here is how to check your alternator. Using an inexpensive voltmeter ($20 at wally world) measure the voltage on your battery terminals with the car off. It should read about 12 volts. Start the car and with it running measure across the battery terminals again. With the car running it should be about 14.4 volts. Careful not to let the test leads fall into the fan while the car is running or well you can imagine what it will do to the meter and leads. Good luck.
 

·
Registered
Joined
·
363 Posts
Smitty said:
Sounds to me like the regulator inside your alternator is bad. Lights dimming because of the heater is no big deal because the heater is one of the largest electrical loads in the car (normally). You cant just replace the regulator usually so it looks like you'll need a new alternator. Here is how to check your alternator. Using an inexpensive voltmeter ($20 at wally world) measure the voltage on your battery terminals with the car off. It should read about 12 volts. Start the car and with it running measure across the battery terminals again. With the car running it should be about 14.4 volts. Careful not to let the test leads fall into the fan while the car is running or well you can imagine what it will do to the meter and leads. Good luck.
actually for proper charging it needs to be at least 13.5 volts. But the voltage has really nothing to do with the lights dimming though. They only require 12 volts to work. The bas amperage is what makes them bright or dim with other things running. Heaters use alot of wattage or power. Power is equal to voltage (in this case 12) multiplied by the amp draw. 105 amps by the alternator at 12 volts is enough to run anything in the car. Alternators run at 13.5+ in order to charge the battery that is the only reason. Everything else is designed to run on 12v. Lighst dimming means bad ground or that the alternators brushes are weak not allowing the field to be used properly (transmitting the amps to the vehicle). If the alternator teast show 13.5 volts the battery is receiving a charge b/c it only takes 2 amps to charge it at 13.5 (basic principle of a trickle charger.) But the auto stores have miditronic testers (at least they should.) This can test the output and the diodes in the vehicle. Generally if the diode ripple is not good it is wiring not the alternator. A alternator doesnt just work it requires input voltage to the regulator to work...........
 
1 - 14 of 14 Posts
Top