Voltage drops to 10.5 to 11 when headlights and foglights are on, need help

[MustangLife]

Ok, heres the scenario. I have a double din pioneer head unit, its bright and does all kinds of cool stuff, ipod interface built in and bluetooth built in. A radar detector and a iphone charger. 1000 watt kenwood amp and the factory mach 460 still installed.

Voltage when the car is on lights off. 13.5 -14.0 volts. Even when the system is on radar detector charging my phone everything. The voltage never drops below 13.2

When I turn the lights on. The voltage drops to 11.5 to 10.5 which is way to low for a car. Especially when that voltage is needed for the lights to provide output. For lamps to work ....

100% they need 12 volts.
75% at 11 volts.
50% at 10 volts.

This problem didn't start until I installed the aftermarket amplified and subwoofers.

With a severe voltage drop like i have alot of people will say a grounding problem but I didn't have this problem like mentioned above prior to the stereo equipment, So I'm sure the grounding is fine.

They are aftermarket foglights and headlights. Illuminatics from American Muscle with a little bit higher wattage than factory bulbs.

So what do I do to get the voltage back up when the headlights are on. Alternator? Battery?

Thanks
Josh

 

[wmburns]

It may be possible that the load is greater than the alternator has capacity to meet.

To rule other things out, recommend that:
1 Check to be sure the battery terminals are clean and tight. Ensure that the top of the battery is clean.
2 Check the battery. If weak, this will affect the alternator's output.
3 Check the belt. Look for slipping.
4 Have to alternator tested. This will let us know the output. If the alternator is weak, consider replacement.

What happens to the voltage when the other "devices" are turned off? Are the head lights extra bright after market units (draw more current)?

 

[MustangLife]

New serpentine belt maybe 1,500 miles and no signs of wear. No slippage.
Battery is a NAPA battery and 1 year old. Haven't had ot many cold days here in Tennessee.
The battery terminals are tight and clean. Perfect.

If I turn all accessories off, radio, charger, a/c/heat, etc voltage still stays low when the headlights/foglights are on. Headlights don't dim or brighten any.

If I turn the lights off, the voltage jumps back up to 13 or so.

I'm thinking alternator too.

 

[wmburns]

Might be handy to measure the current going to the head lights/fog lights. My son had a recent experience with after market parts. He installed brighter lights in his F150 only to find out several weeks later that the extra current MELTED the body wiring harness connector.

The GT factory alternator is rated 110 amps. That equals 1320 watts (110*12=1320). I bet the amp alone is 1000 watts. Also, remember the alternator will not put out max power at idle.

Remember the alternator has to run all of the other electronic devices (fuel pump, injectors, fan, AC fan, PCM, ect.....).

Does it make any difference when the fog lights are turned off? Consider testing by re-installing the factory lights.

I really suspect with the big electrical loads installed, an alternator upgrade will be needed.

 

[flstang65]

Sounds like you might need a stronger output on your alternator.

 

[Shiroelex]

A thousand watt amp doesn't need a thousand amps to run. I would say it sounds like an alternator to me. Remove it and take it up to Autozone. They test them for free, and the machine does a pretty good load test on it. It's possibly one of the easiest alternators to remove out there. I'd been researching a 3G alternator swap for my 81 Bronco, and I can get a 200 amp for 110 bucks, so I'm sure there's a decent sized alternator out there for the 'Stangs that isn't too horrible on the wallet. I ran a 2500 watt amp on my stock alternator and 6 year old battery with no problems, so I'm gonna guess yours might be on it's way out.

 

[patman0911]

If the problem didn't start until after you installed the aftermarket amps then I would try bypassing them and see what happens. If they've got they're own power feed direct from the battery then unhook it or remove the fuse if it's near the battery (which it should be) and see what happens with the voltage without the amps.

The amps shouldn't be pulling that much current when they're idling so with the radio off, your voltages should be normal. Even at full blast, it's almost impossible to pull anywhere near the full power rating from an amp with a music source - you should see the lights dim momentarily with big bass hits but the voltage should pop back up to normal in between.

As wmburns pointed out, the alternator puts out less voltage at idle and if you've got underdrive pulleys, it's even worse. With the lights on and the A/C at full blast, what's the voltage at 2000 RPMs? Does the voltage come up if you bump it a little above idle.

I'd get your battery as well as the alternator checked out. The battery may be only a year old but it may be weakened if the alternator isn't charging well and it's having to supply a lot of juice. 10.5 volts is pretty low.

Again, since you said it started when you installed the aftermarket amps, I'd suspect something related to that. Either the demands of the new audio system are too much for the alternator and it has killed it or it's drawing way too much current due to a short in the sub wiring or a bad connection in the amp wiring and grounding.

 

[n0v8or]

Josh, exactly where are you contacting the elecrical system with your + and - meter probes?
Do you have any other obvious symptoms like less road illumination at night and/or dimmer interior illumination?
When you installed the Kenwood amp, did you connect the negative power lead to chassis, or run a new heavy wire all the way back to the battery - terminal? Where did you locate the amp?

With the engine at idle, you you feel a momentary dip in idle speed when you turn on the headl/fog lights? If the windshield wipers are on at low speed, do they slow down when you turn on the head/fog lights?

Sorry to ask so many questions. I'm trying to deduce if you may be obtaining false readings because of probe location, and not really have a problem at all.

 

[flstang65]

I had 2 Kicker L7 Solobarics with a Kicker kx1500 watt amp in my ex's car. It took a 200A alternator, optima red top and a 2 farad capacitor to fix the issue.

 

[wmburns]

Sorry to ask so many questions. I'm trying to deduce if you may be obtaining false readings because of probe location, and not really have a problem at all.

At the risk a beating a dead horse, the OP stated that the Head lights were dim. I suspect this caused the OP to measure the voltage in the first place. The dim headlights coupled with the measured voltage is pretty compelling evidence of low voltage.

It would also be handy to know the voltage reading at serveral points. For example, if OK at the alternator/battery but low at the headlights, this could indicate a problem with the wiring to the head lights (melted/wet/loose).

IMO, it would help if the OP posted the wattage difference between factory lights and the aftermarket units. It would also help to know the wattage of the fog lights.

Of course it would help to know the current draw as various devices are turned on. However, this would require an ampmeter and shut to be installed (a fairly large shunt at that).

It could never hurt to inspect the grounds through out the car. Look for dirty/loose/corroded frame grounds. Just as it could never hurt to clean the top of the battery, clean the battery terminals and insure they are tight.

 

[Notchbck93]

Now if you only had a meter with an amp clamp you'd be able to see if your alt is putting out the full amps at idle and just isn't able to keep up with your new system.

I venture to bet he needs a higher rated alt. My stock GT dims the lights a bit under full defrost in the winter time, so I could definitely see it having problems running any serious radio set up.

Ford sets their cars up to run everything that came from the factory and that's just about it.

I'd also be checking for voltage drops at all the connections and the cables themselves, both positive and ground!