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braineatingalien 01-10-2013 10:18 PM

Alternator works randomly
I've done quite a bit of research, but I wan't to make sure I don't waste my time. My 2007 ZX3 hatchback Focus recently is having charging problems. The alternator seems to be working on and off at times. While driving and when its not charging sometimes I can rev the engine up to 5k+ and it will kick the alternator back in gear and start charging again for a while. Does that sound like an alternator problem. And why would it work randomly. I'm worried I will take it in to have it tested out and they will say its good when its really not. What should I do?

mikeeshaq 01-11-2013 07:18 AM

Assuming that your battery connections are TIGHT and will not move at all sideways

Then maybe it is your three prong connector that controls the alternator function that is plugged into the alternator. Lots of instances of that connector going bad or perhaps the wires leading up to it.

focusmaniaczx3 01-11-2013 07:29 AM

had a similar issue with mine a few months back. turned out that the post that the main power wire screws onto on the alternator had somehow become partially disconnected. and i dont mean the power wire was trying to come loose from the alternator. i mean the post itself was trying to fall off the alternator. get a hand on the main power wire on the alternator and see if it wiggles at all. also check all of the connections going to the alternator to make sure they are firmly connected, there should be no wiggle room at all, everything should be very snug. also check the power wire where it connects to the battery. if that connection has come loose it could be the cause of an intermittent issue.

rambleon84 01-11-2013 07:57 AM

My 2007 started doing that last year. The car would actually shut off once or twice at stops but revving it kept it alive long enough to get home. Then the next few days the car was back to normal. The telltale sign that it is going out altogether was when electrical things started not working right, even got a message on the stock head unit. Then it died on me while driving, all electrical shut off; gauges, lights, everything. I had the alt and battery tested, the alternator wasnt doing its job. Ended up having to replace the alternator, since then everything is back to normal 100% and happy again.

Similar issue happened with my sisters '07. Her shop said it was the battery only for the new battery to die on her while on a trip. Replacing the alternator fix the problem and she had been issue free for the past year.

braineatingalien 01-11-2013 10:32 AM

Okay, thanks guys. I am working on it today. I guess I will check connections and if everything looks good. I will pull the alt.

whynotthinkwhynot 01-11-2013 10:40 AM

I agree, it's time to start planning on replacing the alternator. So far, the 05+ Focis don't seem to have alternator plug-in connector problems that are fairly common on the earlier Focis. I do not know why this is, and as those cars age it will surely become more common. There are ways to watch alternator output while driving, but it's more for curiosity at this point. You just need a new alternator. Here's where I make my plug for you finding a local rebuilder- because that's a trademark of mine. You support your local small businesses, also in my experience it is much cheaper, and more reliable. Local automotive electrical rebuilders are in every municipality. These businesses might disappear as parts swapping DIYers get wooed by lifetime warranties, so reap the savings and benefits while you can. I got mine rebuilt for $80.

To double check your alternator problems use the electronic odometer method and monitor voltage while you drive. This will tell you if you're having problems with losing voltage via the alternator while driving, low battery voltage before starting, or high alternator voltage while driving. High voltage can kill your battery, and is not good for the rest of the electrical system either.

whynotthinkwhynot 01-11-2013 10:41 AM

Wow... talk about two seconds too late.

1turbofocus 01-11-2013 11:08 AM

The 2005 started a new type of ECU alt control at idle the ecu only shoots for 12 volts depending on load , engine temps and batt temps etc

Low voltage warning wont come on till 11.8 , proper working voltage is only 12.8

Then there is a timer that allows low voltage at idle then after a given time voltage comes back this time can be as high as 255 seconds so be careful testing the alt at idle

If at idle the voltage does not look right but at higher idle (above 1800-2000) voltage is correct this would be normal

Now saying all this the Alt has the ability to charge as high as 14.69 depending on load , engine temps , rpm , batt temps etc


braineatingalien 01-11-2013 11:31 AM

I have been monitoring the voltage through the cluster test mode for the last week and it works randomly while driving. I tried to wiggle test it and doesn't seem to make a difference. I am getting a few tools now to pull the alternator today. I will keep you all updated and thanks for the help.

braineatingalien 01-11-2013 03:09 PM

Well the alternator was really easy to remove, but I made a mistake. I forgot to disconnect the battery and blew the fuse to the alt. Is that fuse replaceable or can I wire my own in? I don't really want to buy a whole new wire.

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