Ok i found a thread on this but it didnt help my problem. here is my problem. At idle the alternaotr only puts out 12.1 volts or battery voltage. I unpluged the connector and found 12v on one wire and 1.7v on the wire coming from the cluster. Also the cluster displays the battery light. Now sometimes that wire has 11.6 volts and the alternator will put out 13.0v at idle. when idled up only puts out 13.7 volts. i have now put on 2 alternators. What would cause a drop in voltage from the cluster on this wire. Another note: i ran a wire direct from battery to the cluster wire and the alternator still only put out 12.1v at idle. Any help would be great. Im stuck on this one. have been working on it for 3 days now.

 

another note. i charged batteries and tested them seperately. both tested good. according the the wiring diagram it gets one signal from the cluster and the other from battery supply. i am only getting 1.7v on the wire from the cluster. i ran a jumper trying to bypass the cluster and still no charging.

 

I had a battery light issue and got a DC Power Alternator and havent seen that battery light since

My Battery light on dash seams pretty accurate
if one or the other is getting ready to go out
heres some reading material

alternator stuff
http://www.pvv.org/~syljua/merc/TooSeptST07.pdf

and another ripple wave stuff
Powered by Google Docs

 

ok so i tried that and got .04v ac. not enough to show bad diode. after charging the batteries i started the truck and it was charging at 13.1 volts and i had 12.46 volts on the signal from the cluster. then after 1 and half minutes of running the alternator kicked out and the voltage from the cluster dropped to 1.6v. this one just doesnt make sense. help!!!!!!!

 

Well if it running at 12.46-13.1volts and then drops to 1.6volts alternator output isnt the Alternator Bad

mine would never drop below 12.0 volts running but the Battery light was on put that High output Alt on and problems are gone

Electrical problems suck

is this a new Alternator your talking about

 

yes it is new alternator. second one. im wondering if there is a relay or something that controls that signal from the cluster. not sure here. im lost on this one. im usually pretty good with electrical but this one makes no sense to me. according to the schematic there is a fuse but doesnt show a relay. the fuse is good. the battery light only comes on when the voltage drops to 1.6v. when it has the 12v the light is off.

 

when it drops off the alternator is only putting out battery voltage on the b+ post. the wire im refering to is the green and red wire that goes from the plug to the cluster. the orange wire stays at battery voltage. the green and red wire drops to 1.6 volts and the alternator kicks out.

 

The wire to the dash is called the I-sense wire it comes off the pigtail on the alt there is no relay or anything inline with it that I know of

IIRC it does nothing but control the Battery light on the dash

could be possible that the I-sense wire has a short in it

 

k im going to try and pull the cluster and check the wire from the cluster to the alternator and see if there is a short.

 

Not sure if you have this print to look at but helped me alot when I was having trouble with mine a few months ago.

Blade, was it you that sent me a theory of operation? I can look for that post if not. That was very helpful if you still have it. I had my head wrapped around this subject pretty well at the time but it didn't stick. Guess I'm gettin old or somthing.

 

Yes that is the same schematic that I have.

 

Not what I was looking for, but here's some more info:

https://www.ford-trucks.com/forums/9...or-no-ecm.html

Post #4 has a chart showing correct voltages for each circuit of the system with key on, and KOER.

 

Normally, the I wire is not powered until the glow plug timer expires and the glow plugs are turned off. Then the I wire is powered by the cluster, turning on the alternator. So the cluster has the ability to turn off power to the I wire. At least on diesel clusters.

From what you are describing, I would suspect either a bad wire or a bad cluster. I have seen occurrences of the pigtail at the alternator failing intermittently. I'm not sure how you'd check that, other than probing the wire further up somewhere.

 

Hey dchamberlain! We had discussed this a few months ago and you posted a PDF that helped me. Thanks then and I'll pass it on:

https://www.ford-trucks.com/forums/a...9&d=1302918849

Diesel's Mechanical, This is what I was looking for, hope it helps!

 

I hadnt seen this one thanks for tracking it down Rusty