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Discussion Starter · #1 ·
When my radiator fan kicks on (and it has been on a lot since it is 96 in AZ) the dash lights and headlights dim and the engine sounds like it is going to die. I know it is just the alternator kicking in but does this happen to everyone? I mean, if the A/C is running and the fan kicks in the lights go from halogen to a 10 watt bulb. Is my battery on its way out?

Thanks
 

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Looks as if your alternator cant keep up with demand. Car shouldnt sound like its going to die. Take the car to an autozone or a kragers ( its been awhile since i lived on the west coast, cant remember what you have out in phoenix). anyways, they can test your alternator and battery. If you have a multimeter ( can read dc and ac voltage, resistance, amps), you can see what charge your battery has. Do it with the car off. Should read 12.6 volts. ( on dc setting ). at 12.4 volts, the battery is only at 75% charge. If you read like 13.1 volts, turn your lights on for about 30 seconds, then try reading the battery again. Defenitely sounds like you have a bad alternator though.
 

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My lights do the same thing, also when I turn on the fan, they will dim for a second. The local dealer told me it was normal......
Let us know if you find out anything different.
 

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Discussion Starter · #5 ·
Just thought I’d update this problem, since I am not alone with the dimming headlight thing. I did a basic voltage check and it seemed fine, so I let it go for a while, but yesterday I went to Autozone to get some other stuff and I had them test the battery and alternator. Say hello to a 9 Amp Ford alternator. I wonder how much that is going to cost, since Autozone cannot even order one apparently...

So, if you are having this problem you might want to have your alternator checked.
 

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Discussion Starter · #6 ·
Ok, this is just weird. I took the focus into the Ford dealer today and they said that the alternator and battery are fine, but the battery terminal connections needed new pads. The mechanic said that this is "common" on this car. We'll see if that really fixed it when I pick it up tonight...
 

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The lights dimming for a second is normal. It's a huge current draw for that fan to turn on, so it sucks current away from the rest of the car to start up. It should go away promptly. I have a volt gauge hooked up at all times, and you should see it bounce from 14.2v down to 12.9v and back up!


A 9-amp alternator? That's not even 10% of rated power! And, how the heck would battery "pads", which prevent acid leaks, affect alternator performance? All questions aside, the alternator prevents the dimming of the lights. And unless you have 100 Amps of ICE running constantly, your lights should not be that dim.
 

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Discussion Starter · #8 ·
Apparently, spending the $25 at the Ford dealer was not completely in vain. Before, when the radiator fan kicked on the lights would dim while the fan was on, now they just dim for a second and come back. They said there was corrosion under the battery terminals and that is why they replaced the pads. I checked the terminals to make sure they were tight before I took it in and I didn’t see any corrosion (in fact it looked really clean), but I didn’t disconnect them to check under or inside the connection.

BTW, the 9 amp figure is what the Autozone machine read at about 2200 rpm. It would be interesting to have them check it again and see if it is any different now.
 
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