My charging system light in my 2000 F250 keeps coming on and off and very random times. Its been happening for quite sometime now and I finally joined FTE so I figured I would ask everyone what could be causing this. Ive disconnected all the electrical plugs from the alternator and made sure they were in there well.

It all started when I was cleaning my engine not too long after getting the alternator replaced. I dont remember getting any water anywhere near the alternator and cant understand anyhing causing this other than the connectors. It will cut on and then cut right off sometimes and then sometimes it comes on and stays on...

Any thoughts?!

 

Sure sounds like an alternator going south. Have you had it tested? How are you batteries?

 

The ONLY thing that can turn on the charge indicator light is the alternator or a short to ground between the light and the alternator.

The "I" terminal of the alternator (Light green/red tracer) controls the charge indicator light....the regulator inside the alternator is the ONLY input to the light.

 

SOUNDS LIKE "WARRANTY" TAKE R BACK roundthree

 

Well this has been WELL over a year and almost 2 year I believe. Ive replaced each battery once in 8 years. Charge on the batteries is fine and Ive had the alternator tested and they say its fine. The light literally comes on and then sometimes will go off just as quick. Almost as if I hit a bump it comes on and hit another and it goes off....should I clean the connectors/terminals?

 

Check this picture.



There may be a chafed wire causing a short to ground on the indicator control circuit or possibly an internal cluster short......I wouldn't worry about the positive side from the ignition switch through the fuse. If it doesn't work, the light won't come on at all.

 

Thanks for the diagram. I guess Im just going to get in there and check the lt gree/red wire has any problems. I also noticed like 10 minutes ago that the "little tab" that keeps on of the connectors plugged in has been snapped off...could this be causing it? It does seem like bumps cause this more often than anything else. Anyone know where to get a new plug besides Ford? Just solder and plug n play?!

 

Sounds like you are looking in the right place with the plug. Figure out how to make it snug and secure and I think you may have your problem fixed.

 

Welp, the plug is more or less cracked than anything.I would attach the picture I just took, but cant just yet since Im new! I went out and tried to make the light shutoff by moving the plug around and doing everything BUT unplugging it while the truck is running. The light WILL NOT go off no matter what I did. I looked as far down as I could along the wire and it looked like it had wire loom as far as I could see.

How would I check for the cluster shorting out?! I have plenty of 12 volt experience owning my own car audio shop for 6 years so Im definitely confident in wiring, but ripping out my OWN dash...ehh...not so much!

 

Ok, have you had the cluster out before? If so, It's pretty dang easy. Anyway, you will have 3 connectors on the back of the cluster once it's out. There will be a connector with the lt.green/red wire (charge indicator) between a white/yellow wire and dk. green/lt. green wire. Cavity 8 in C250A. If you test this wire and it has continuity to ground with the alternator connector disconnected then there is a short in the charge indicator wire. If there is no continuity to ground with the alt. disconnected, but the light still stays on in the cluster, then the cluster is at fault. However, if there is no continuity to ground with the alternator unplugged but there is continuity when plugged in with the engine running, then the regulator is bad.

1: Unplugged cluster. Testing for continuity to ground on charge indicator wire.
A. Alt. unplugged and continuity to ground....short to ground
B. Alt. unplugged NO continuity to ground....no short.

2: Plugged in alternator. Testing for continuity to ground on charge indicator wire.
A. Engine not running, Key on, SHOULD BE continuity to ground.
B. Engine running....should NOT be continuity to ground.


DO NOT USE A TEST LIGHT. USE A DVOM (digital volt/ohm meter)

 

I see it says you did everything BUT unplug the connector......

Unplug it while the engine is running and see if the light goes out......that will tell you if you have a short in the charge indicator circuit or not. OR a bad cluster.

However, that won't tell you if you have an issue on the "A" circuit to the alternator (can also cause the indicator to light). It's the power feed (exciter) to the regulator to let the regulator know that the ignition switch is on.

 

Very nicely done Cody!

 

Alright, Ill go do that now...didnt know I could do that and not do something "bad" or not!

 

Not going to hurt a thing....just watch out for moving accessory pulleys and the belt!! Don't want to hurt yourself!

 

Ok, I unplugged it and the light went off....plugged it back in and came right back on...