How many amps should an 01 Ford Focus SE's alternator be putting out? Mine's only doing about 18...should I get this changed immeditately? My car wouldn't start this morning when it was really cold outside for the first time this year. I know the battery is ok. Thanks!
How do you know it's '18'?
If you are looking at the dash gauge that means 'volts'.
Max charging voltage is to be around 14 1/2
If it says 18, that is too high and the alternator is cooking your battery. There is usually a red mark on the gauge at 18. Is that where your needle is pointing?
No, the battery was about 14, the alternator was pushing about 18 amps according the machine the guy at Advance Auto Parts was testing with.
18 sounds low to me... Fred
A quick google search leads me to believe it's rated at 110 amps.
well, then.. it's bad.
didnt the guy tell you that?
Was the charging system put under a load when the test was done? Was alternator ripple checked?. If the charging system isn't loaded down with either a carbon pile or at least turning on all the accessories, 18 amps may be an appropriate reading. For any testing to mean anything, it needs to be performed properly.
If the battery is original, I would consider having it tested as well.
We are assuming the guy knows how to check the alt using a load tester. If he did check it with a load test it should put out about 70 amps or so at a high idle.(I'm guessing, but around there) 18 amps is perfect if the battery is only needing 18 amps at the time.....If you load it to max, it should be way higher. Did that make since? Maybe you should have it checked at a battery shop....Although I have had to teach a kid at a local battery shop how to check my battery and alternator before...Oh and how to lube my front end parts at a local lube shop, but that's another story.
Reading the whole thread here points out the need to include ALL information on the problem when you originally post it!.
What I gather: The OP had trouble starting his car in the morning
He hadnt had this problem before
He took it to a parts store and the clerk tested to Alternator output while in the car
The Alternator was apparently putting out 18 amps while idling
- no indication as to whether lights were on at time etc
Because of the info posted, some (me) MIGHT have concluded that the OP was referring to a dash voltage gauge, as IT is marked "18" at top of scale. If OP was older, we assume he might assume that was "AMPS"... unfortunate coincidence relating to 'numbers associated'
So if ALL the pertinent info had been included, then we would be able to respond as follows:
For proper testing, the ALT has to be removed and tested 'on Bench' under a full load. And output ripple measured, as well. (This shows if a portion of diode rectifier assy has blown)
If that battery is the original, then there's a real chance it isnt good.. despite casual testing results. Certainly its life expectancy is almost up even if it DOES 'test good'.
"Cygnus311" wrote:
The alt doesn't HAVE to be removed to be tested properly. The place you take the car needs to have the proper equipment to test it in the car. Much easier to just drive up then to remove it and take it in, test it, if its good re-install it.....
Indeed, in car is THE BEST place to test the alternator - after all, this IS a charging SYSTEM test.
Under normal circumstances, the alternator will only produce enough power to fulfill current requirements at the time of the test. The alternator field utilizes duty cycle to maintain system voltage. If power requirements are low, duty cycle will be low and current flow will be low. By loading the system with either all the accessories (mediocre) or a carbon pile (best), we can present high requirements to the charging system and then read the alternators available output. Most modern AVRs have a ripple test function.....
The crux of the matter is performing the test procedure properly or at least adequately.
FWIW, I have seen more bad batteries make an alternator look bad than vice versa......
I'll fall on my sword and defer to Warman, as usual.. ... much qualifying needed to justify my position on bench testing..
Point being Alt needs to be tested under Independent load and that procedure is more likely to occur on the bench - just in my opinion-
And Warman knows his Duntov!
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