2012 Focus battery light on and AC/heat/defrost acting funny. Where could I start?

I'm not looking for a solution, just somewhere to start because I want to see if I can figure this out myself before taking it to a shop. I do not know much about automotive electrical systems and Heat/AC stuff because I've never had to bother with it before. However, this is the wife's car so not bothering with it isn't an option

These are the things that are happening. I have some ideas but I'm not sure what could be related to what or what could be causing what:

A year or more ago the battery started coming on intermittently. During the summer Belle Tire did a check when the car was in for tires and said the alternator failed the test, and that was the reason for the battery light. The car has never had any problems starting or cranking so we made sure we had jumper cable in the trunk and waited to see if anything happened. Months later the battery is charging fine. Are there different ways an alternator can go bad?

We noticed during an early summer road trip that the A/C stopped working a few times (for a few minutes at a time, stopped blowing cold and the A/C symbol on the console wouldn't light up even when I pushed the button) on really hot days. The airbag light also came on for a ~30sec right before the A/C would stop working. That happened for a couple days and then didn't happen anymore. Hasn't happened since, even during the next hot road trip to Tennessee in late July.

Present day:

Now the battery light is on constantly and the wife says the heat isn't working the way it should. We'll start it in the morning and turn on the defrost to clear the fog. It seems like it doesn't start to get hot, no matter how long we let it idle. But when we start driving it turns warm fast and clears up the windshield fast. She says last year it would warm up and clear the windshield in the driveway within a few minutes of starting the car.

I don't know if that could be a problem related to whatever is causing the battery light or not. As I said, my knowledge of this stuff is limited to "Oh the a/c isn't working on my '94 Escort, good thing they make bypass pulleys!"

Hopefully I didn't ramble too much. Any input would be appreciated. Looking forward to another learning experience

Start with replacing what you know is bad: The alternator.

Right, the battery/charge light comes on when the alternator is NOT charging the battery.

On high mileage alternators the brushes get worn and at high rpm lose contact.

Some of your other problems indicate low voltage. Soon the car won't start.

Get an inexpensive volt meter. Test the Battery at the terminals engine not running 12.5 Volts for a fully charged battery. Then, run the engine at a medium rpm, 1500. You should have a little over 14 volts. Do not test at idle.

After thought, poor battery terminal connections are the first thing to check.

It is also technically possible for an alternator to fail intermittently, and most systems will function over a wide voltage range. It actually takes quite a bit of driving to kill a battery that isn't charging, depending on the car and battery. Replace the alternator and see what happens.

Do a visual check of all wiring and connections.

Look for corrosion .

Bad grounds are always a possibility.

Is the water pump on the serpentine belt or the timing belt/chain? If on the serpentine belt, that would be common item between all the affected systems. Then again diagnostics was a big reason I didn't pursue a career as a tech after 2.5 years of training.

Ok, so starting with the alternator. I was skeptical when they told me it was bad because

1) It's only 4 years old with ~70k miles on it. (But if we're honest I haven't been impressed with Ford's build quality on this car)

2) At that point the light had been on for months and no apparent problems. (If it's failing intermittently as gearheadE30 said that might make sense)

3) It's Belle Tire.

I reeeaaally don't want to start with throwing parts at it right away especially since an alternator costs $200+ If I'm going to replace it, I want to be pretty sure. So, I'll dig out the old volt meter, start checking the stuff you guys have suggested, and go from there.

Also, I can't find a DIY write up on the web for replacing an alternator. Seems these cars aren't old enough to have people writing on the internet about replacing this kind of stuff yet.

So thanks, everyone.

Sounds like your alternator isn't alternating

But seriously, your battery is there to start the car, the alternator is there to maintain a battery charge and keep a constant voltage to the accessories. If you have accessories that aren't functioning properly, most likely the voltage regulator in the alternator has or is taking a crap, but in today's throw away society, you have to replace the alternator.

But yes, check the battery connections, etc first before you drop the money on an alternator.

Sounds like your alternator is bad and your coolant is low to me.

Get a voltmeter and test. Only way to be sure.

I would say the alternator isn't working a full capacity. Fock do weird things when the battery is getting low on charge. I always knew when my battery was going bad because the speedometer would jump to full scale, the a/c would cut off, and the odometer numbers would turn backwards.

So I went to pop the hood and give things a closer look and... the hood won't unlatch. The Focus and I are not on speaking terms right now

I didn't even think about low coolant. Thanks for that tip.

BlueInGreen44 wrote: So I went to pop the hood and give things a closer look and... the hood won't unlatch. The Focus and I are not on speaking terms right now I didn't even think about low coolant. Thanks for that tip.

And there is a recall for the door latches not keeping the doors closed.

So far my 2013 Focus has been trouble free. It has 43K, bought it with 23k.

My old Focus had similar issues and it turned out to be a bad wiring harness at the alternator. The plugs tend to go bad often enough that the aftermarket has created a replacement plug with about a foot of wiring attached. You have to cut back the old harness then splice the new one in. On my car the voltage was jumping all over the place but always kept the battery charged. I found the problem by jiggling the wire harness while the engine was running. I could get the battery light to turn on and off depending on how I held the plug. I tried cleaning the contacts and adding dielectric grease. It helped but didn't solve the problem. Once the harness was changed everything worked again like it should. I've had a few Fords including the Focus. They all seem to have weak charging systems.

Also if one of the alternators diode trio has failed and spiked it COULD have shorted the BCM causing a failure in the temp door control leaving the AC blend door open causing the AC to not work properly and turn off as well as a cooler than requested temperature through heat or defrost settings.

Personally I'd spend $100 at the dealer on this one.

trucke wrote:

BlueInGreen44 wrote: So I went to pop the hood and give things a closer look and... the hood won't unlatch. The Focus and I are not on speaking terms right now I didn't even think about low coolant. Thanks for that tip.

And there is a recall for the door latches not keeping the doors closed. So far my 2013 Focus has been trouble free. It has 43K, bought it with 23k.

We got the bulletin for the door recall a few weeks ago.

A quick search of some Ford forums indicates that the newer hood release mechanisms are more fragile and prone to breaking or sticking. C'mon guys, it's not like opening a hood or keeping doors closed is a newly developing technology.

If it were just my car I would be considering replacing it something more sturdy. If it's four years old and having little issues like this I hate to think of what it will be like five years from now. But, the wife loves it so it's likely staying for the long haul.

The cable operated latch is certainly more complicated than it needs to be.

150k miles here on a 2012. Chugging along well. Wife wants a bigger car next year though because kid stuff.

John Brown wrote: Also if one of the alternators diode trio has failed and spiked it COULD have shorted the BCM causing a failure in the temp door control leaving the AC blend door open causing the AC to not work properly and turn off as well as a cooler than requested temperature through heat or defrost settings. Personally I'd spend $100 at the dealer on this one.

This. The alternator could be feeding AC voltage in to the system, which can really screw with DC operated controls.

It could also be a bad battery causing (bad cell, sulfated, shorted cell) the alternator to under/overcharge. In the very least you need to have the battery and charging system checked again, especially since the light is staying on now.

Start with the simplest. Local AutoZone can check the battery in the car and hte charging system to get you started. It wasn't uncommon on the newer Acuras that use a ton of juice for the battery to cause all sorts of issues. Basically, the battery is a large surge protector to handle the extra surge of juice certain accessories like AC need at start up.

Your Focus has a "Test Mode":

Hold down your odometer reset button, turn your key and start the car, continue holding the button for a few seconds, and you'll get into "test mode", where you can scroll through a bunch of different readings by pressing the button.

Battery voltage level is around 12 button presses in.

I found test mode! Says the battery is at 13.8v with engine at ~1500rpm. Same v. at idle. Also, playing with Focus test mode is a great way to pass the time while I'm waiting for the wife to come out from the doctor office.

Edit: and this is all I can check without being able open the stupid hood.

The alternator is the only thing I had to replace on my 2001 Focus which I just sold this year. Alternators seem to be a problem with the Focus as I know a number of people who have had to replace theirs.

In reply to BlueInGreen44: 13.8 is low. should be app. 14.3 That is not the battery it's the alternator charging rate.

etifosi wrote: Your Focus has a "Test Mode": Hold down your odometer reset button, turn your key and start the car, continue holding the button for a few seconds, and you'll get into "test mode", where you can scroll through a bunch of different readings by pressing the button. Battery voltage level is around 12 button presses in.

Does that work with push button start as well?

iceracer wrote: In reply to BlueInGreen44: 13.8 is low. should be app. 14.3 That is not the battery it's the alternator charging rate.

It depends. Some charging systems are temp compensated. My Jeep compensates more than any I've seen. There's a temp sensor under the battery. I've seen it over 15 volts on a cold morning in the winter. In warm weather with the engine bay heat soaked (battery warm), I've seen it down to 13.7 or so.