I think idle speed should be 650 to 750 depending on how much creep you get out of the trans. You need to find out why its being allowed to be slower. It was so easy in the old days - you just adjusted the carb/linkage to get your choke closure, fast idle, hot idle and throttle plate opening. Now I guess you have to ask the ECU 'What the hell are you doing? Anyway there's a spec on it which you should know before trying to 'fix' anything. Maybe 500 RPM hot and in gear is correct.

 

Junk it, is it worth those few buck to get stranded on a holiday weekend some day?

 

It is supposed to be in the 50's today so I'm gonna put an amp clamp on it when I get home from work and see what kind of current it is actually pushing. If it isn't meeting Ford spec (There's a chart in the ford service manual) I'll try calling the support number on the paperwork that came with the alternator, and see what they say, I may also call AutoZone corporate and see what they say.

I don't know what to say about the idle speed, it has always had a low idle speed, and it idles smooth as butter.

Another thought I had was, maybe the alternator isn't broken in by the re-manufacturer. Alternators have brushes inside which need to wear in to pass full current, maybe I need to run it for 100 miles or so and check it again?

 

"current" is determined by the charge in the battery.. If the battery is FULL, you wont see much current..... The VOLTAGE should be basically constant.. If you cant hold but 12.5 volts at idle, then you have a VOLTAGE regulator problem. If your at 13.5- 14.5 volt range, then that might be acceptable.

 

The Idea is to check if the alternator is capable of providing the specified current at idle RPM. There is a graph in the Ford service manual that specifies a "Good/No Good" current threshold for a given engine RPM.

I was going to turn on several loads (high beams, heater fan on high, rear window defroster, etc ) and measure current from the battery. If the alternator is delivering enough current for these devices there will be no current flow from the battery. If the alternator isn't supplying enough current for all these devices (the load exceeds the alternator's capacity), there will be current flow out of the battery. If there is current flow out of the battery, I will measure the current the alternator is supplying, and if it does not meet the Good spec from the service manual chart for the given engine RPM, it does not meet OE spec and is faulty.

This is the procedure I got from an full time automotive diagnostician.

I did see the voltage drop below 13V a couple times with high loads on the new alternator, and the 13.69V I measured previously wouldn't bother me if the PCM wasn't telling the alternator to output 14.56V. If the regulator was working properly, the alt should be at full field at this point. Now it is possible the load was exceeding the alternators output spec, if that's the case, I won't worry about it.

 

Ford Minimum spec for 525 RPM is about 25 Amps. With the headlights, heater fan, and defroster on the load is about 61 Amps, the Alternator is supplying 55 Amps with the remainder 6 Amps coming from the battery so the voltage was only 12.93V but the alternator is exceeding OE spec at idle in gear, so it appears to be OK.

 

OK... I would agree you are OK as long as the voltage jumps up above 13.5 volts when your around 7-800 RPM............. I question how you got a 61 amp load out of head lights and blower motor ? ........ but I think your safe.