Check Charging System Light

[BatDan]

2005 4.6L GT
New 160a output alternator - https://www.dbelectrical.com/products/alternator-high-output-160-amp-4-6l-mustang-2005-2006.html
New fused 4 gauge power cable - https://www.americanmuscle.com/premium-power-wire-kit-9414-excluding-gt500.html
Rest is stock

Before everyone says alternator/battery - both are good. Multimeter at the battery posts shows 12.5v at rest, 14.5 at idle. OBD Fusion app shows similar, as well as 13.3-13.8 going down the road.

Was getting P0340 code, so I installed a new alternator (old was going bad - no surprise) and power cable. All connections are solid.

Fuse 43 is good. 200a inline fusible link on the new power cable is good.

Now I'm getting "Check Charging System" light, but nothing seems to be malfunctioning.

I haven't tried unhooking the battery to reset the computer, yet, but it's on the list.

Suggestions PLEASE!

 

[Dino Dino Bambino]

The only thing I can think of is possibly a bad ground from the alternator. The CCS light is a sign of an ongoing problem and resetting the computer won't make it go away.

 

[07 Boss]

Maybe the new one is bad. Just saying. I had a brand new alternator, fresh out of the box, at Ford be bad upon install. And I can almost guarantee that yours is a rebuild. And if you ever do need to change your alternator again go with a 2010 one instead.

 

[Pentalab]

Maybe the new one is bad. Just saying. I had a brand new alternator, fresh out of the box, at Ford be bad upon install. And I can almost guarantee that yours is a rebuild. And if you ever do need to change your alternator again go with a 2010 one instead.

OEM alternator is 135 amp. This aftermarket unit is 160 amp.

 

[Juice]

13.3 while driving is low. Yes, it is still charging, but not very well.
Either you battery is not fully charged, or your new alternator is not working 100%

Ps: I only buy NEW alternators and waterpumps. Had spotty luck with reman shit.

 

[Dino Dino Bambino]

13.3 while driving is low. Yes, it is still charging, but not very well.
Either you battery is not fully charged, or your new alternator is not working 100%

Ps: I only buy NEW alternators and water pumps. Had spotty luck with reman shit.

I agree that 13.3v while driving is quite low but that also depends on how much electrical load there was at the time from items such as the AC, cooling fan, infotainment system, and driving lights. Regardless, that voltage isn't enough to trigger a CCS warning and a battery light.
His battery was showing 12.5v at rest, and that suggests it was pretty well charged
I doubt that the replacement alternator is weak because the battery was showing 14.5v at idle (2.0v above resting voltage). However it could have a bad rectifier (diode) assembly (these usually aren't replaced in reman alternators) so I'd suggest the OP conducts an AC ripple test.
You'll find that every "new" 3V alternator made in USA is a refurbished used core. I doubt that even the Chinese made PA alternators are brand new and they don't exactly have the best reputation for reliability either.
As for water pumps, new ones are plentiful and inexpensive so it's a false economy to buy a reman unit

 

[07 Boss]

I believe I have one of the last Brand New alternators sitting in a box on the shelf. I bought it when I saw it and then when it came time to replace the one on the car I went with a 2010 one instead. By the way I have gone through 5 alternators including the one that was bad out the box. 3 were done under warranty.

 

[Juice]

My running volts never drop below 14.3, with everything on, full AC and with EPAS.
Just sayin'

 

[DieHarder]

Suggest poor/bad grounds may be an issue here. Have some experience in this having dealt with it until I found I needed to add another ground (4 gauge) from the body of the alternator back to the body ground located on the passenger strut tower. To test if this is an issue in your case just take a pair of jumper cables and connect the negative terminal to a mounting bolt for the alternator and clip the other neg end to the passenger strut tower ground. If your running voltage rises back up to 14.5vdc you'll need to either clean/refurbish all of the engine grounds or add another ground from the body of the alternator to ensure the alternator ground is at the same potential as the body ground. May also be the reason you're burning through alternators.

 

[BatDan]

All signs are pointing to bad ground. Diodes are good (tested). Is the voltage regulator separate from the alternator for the 2005?

 

[BatDan]

@DieHarder Only the first replacement (so far)

 

[DieHarder]

Easy check you can do to verify poor grounds is to do voltage drops with the engine running. Simply touch ground on the passenger strut with the negative terminal of a VOM and test various points on the engine (alt body; engine block; etc and from the alt body to various points on the engine) with the positive terminal. If you read any voltage (no matter how small) that’s a voltage drop (which means there is a difference in the ground potential between that point and the body ground at the passenger strut tower which is the main ground reference). That said the way to fix it is to clean up the grounds/replace the ground/battery lines/or (easiest) add a ground from the alt body back to the passenger strut ground. This will ensure the alternator is at the same ground reference as the body ground.

There’s a write up on my experiences with pics if you’re interested - “Finally figured out my low voltage issues “ or something to that effect. Good luck.

 

[Pentalab]

13.3 vdc, while driving, is way too low. You have a bad grnd somewhere. The 05-10 cars don't have epas, so the load is way less. I measured 14.75vdc across the battery terminals..idle or driving. (2010 GT).

To test for 1 or more bad diodes, put the DVM in AC mode, and put it across the battery terminals. It should be 50 mv AC or less. The alternator is a 3 phase type, which uses 6 x diodes. If 1 or more diodes has failed shorted, it will pump raw AC into the battery. Batteries don't like AC, which will destroy a battery in < 18 months.

 

[BatDan]

Voltage drop test reveals no drops, diode test yields 32 mV AC (third party test showed all good, as well), alternator mount bolt to passenger strut tower ground results in no change to idle voltage (14.3-14.5).

Based on all my testing, the battery and alternator are good. I'm going to try reinstalling the original 6 gauge power cable and see if that makes a difference (only other thing that was replaced).

Beyond that, I can only think computer or the CCS light itself.

Appreciate all the advice. Keep the suggestions coming if anything else comes to mind.

 

[Juice]

Pcm is programmed to maintain 14.x v when running.
Pcm is flagging with "check charging system.
Idle volts seem OK to me, but drop into the 13s while driving.
Logical thinking tells me your new alternator is weak and cannot deliver the AMPs needed to maintain 14+ volts.
Get another alternator before you spend too much time chasing ghosts.

 

[BatDan]

Pcm is programmed to maintain 14.x v when running.
Pcm is flagging with "check charging system.
Idle volts seem OK to me, but drop into the 13s while driving.
Logical thinking tells me your new alternator is weak and cannot deliver the AMPs needed to maintain 14+ volts.
Get another alternator before you spend too much time chasing ghosts.

It's a - supposedly - new 160 amp output alternator (not sure how best to verify that).

 

[Deon Lee]

I have a 2008 gt kept getting check charging system flash on the msg center on the dash. Never had any problems with car starting or any other concerns other than the check charging system would pop up occasionally. I bought a brand new 2010 alternator had to changed the ends on the wire and grind a little but even with under drive pulleys since I put the 2010 alternator on I haven’t had the check charging system come back on. And also before doing the alternator swap everything was tested and checked out. I decided to change the alternator anyways and it fixed the problem.

 

[Laga]

After buying an alternator at Advanced Auto, the battery would not keep a charge. I talked with counter guy at AA if they still did bench testing. ( They used to when they were Carquest.). He said they didn’t anymore, but just bring the alternator in for an exchange. He said they have bad alternators all the time. After swap, no problems.

 

[DieHarder]

Voltage drop test reveals no drops, diode test yields 32 mV AC (third party test showed all good, as well), alternator mount bolt to passenger strut tower ground results in no change to idle voltage (14.3-14.5).

Based on all my testing, the battery and alternator are good. I'm going to try reinstalling the original 6 gauge power cable and see if that makes a difference (only other thing that was replaced).

Beyond that, I can only think computer or the CCS light itself.

Appreciate all the advice. Keep the suggestions coming if anything else comes to mind.

At 14.3-14.5 vdc that idle voltage is fine. In my own case going down the road I never see anything lower than 14.0. The other pieces/parts that degrade over time are the main battery cables/fusible link due to age/corrosion. Main battery cables can still be purchased ($60 - 100). I replaced mine and saw 1.5v increased output (13.0 - 14.5). Of course my cables were old and I added a ground from the alternator back to the passenger strut tower main ground. Been fine since.

 

[09brian0]

Just adding the simple stuff, check for loose/worn belt?