Check Charging System Problem

[mike9999]

2005 Mountaineer

Started having check charging system light come on last summer. Put in a new alternator (not remanufactured) in August. Light went off and stayed off until November. When it came back on in November shop couldn't find anything wrong with it, except battery showed lower voltage, but still within normal limits. With lack of any other problem they did replace the battery at that time. Light went off again until December. Happened to be visiting my brother in law who was a Ford technician and he recommended the belt tensioner since the light was intermittent and seemed to occur mostly under load. Replaced the tensioner and again the light went off.

Stayed off until April. When it came back on I performed a voltage check with a voltmeter, and received normal results, 12.2 on battery with car off, 14.6 with the car running.

At this time I disconnected the battery and tested the voltage at the alternator, again normal. When I reconnected the battery, the light was off and stayed off for two more weeks.

Now it's back on. I haven't disconnected the battery yet to see if that makes it go off again. As I was driving it last night it was going off almost constantly. I just happened to run a systems check test and again the light went off and stayed off.

Has anyone seen anything like this. It doesn't seem like there is really a charging system problem since I have driven it for sometimes weeks with the light on (intermittently). Could there be some problem with the warning light system itself?

Thanks.

 

[TechGuru]

12.2 off is LOW! Full charge is 12.6

What brand of battery and alternator are you using?

 

[mike9999]

Sorry I got my numbers confused. The voltage with the car off was 13.2 right after turning off the engine. A few hours later it was 12.7.

The battery is a Duracell. The alternator is Duralast Gold and it was brand new.

 

[Number4]

When it acts up, wiggle the connector on the alt which sends the signal to the PCM. Might have a bad connector. It'll work for a period of time after jostling it, until it gets corroded or the gremlins get to it.

 

[Number Twelve]

The voltage with the car off was 13.2 right after turning off the engine. A few hours later it was 12.7.

Your voltage numbers are exactly where they should be so the problem must be in the detecting circuits. Quit chasing a charging problem and look to why the car can't see these excellent numbers.