Feel free to read my rambling below, but I did find this out. Clip disconnected I have 12v again. Start the truck no charging, green wire is 7v or so plugged in. Jump 12v to green wire and alternator turns on and charges. Battery light is dim when key on and goes o ut when alternator clip is removed. I read RonD's info about how the light works.


Hi everyone,

Been fighting an alternate no charge issue. Found fusable link was bad, temp bypassed. Now the green wire is getting 7v not battery. When I started it was getting battery but slowly got lower. I have traced it back to an issue in the cluster but am stumped.
I have 12v to the battery bulb but only 7v coming out. I have tried a few different bulbs and sockets. Nothing changes. The resister in the circuit shows 385K ohms when the socket is removed and 16 ohms when installed. Removed or installed the socket, with bulb installed, shows 16 ohms.

I read the 390K resister is to simulate the warning bulb if it goes bad. With the bulb removed from the cluster I now get 5V on the green wire. Even more confused now.

Testing the green wire from the alternator tot he back of the cluster is 2 ohms.

It is such a simple circuits that I am very confused.

When I jump battery to the green wire alternator works so I know it's in the green wire circuit.

Any help would be appreciated. Thank you

 

Welcome to the forum

Always good to include the Year of the Ranger in a post, the info in your Profile doesn't show up in the post

You have a 2003 Ranger according to Profile?

Yes, the Battery Light circuit is very simple

(Cab fuse box)Fuse 11------------(yellow wire)--------------(instrument cluster)Bulb------------(light green/red wire)--------------------alternator

The 12v bulb does have a bypass resistor with it, in case bulb burns out you wouldn't loose Charging

So your 7v and 5v(no bulb) would be correct, the resistor has higher resistance than the Bulb so all voltage would pass thru the bulb, the lower resistance circuit, unless it was burned out

But because you are getting the drop from 12v down to 7v would mean that fuse 11 voltage has no AMPS, so corrosion or a bad connection on the yellow wire or in fuse box
A volt meter has no resistance to "load" test the voltage, as it should be
Voltage is what you are reading but AMPS are what PUSHES the volts thru the wiring, if AMPS are limited then when a device(bulb) uses Volts you get a drop in volts because there is not enough pressure PUSHING AMPS thru the Bulb, so the 5volt drop down to 7v
It could also be an issue in the cluster itself

If Battery Volts were 12.5v at battery, Key ON
Then Fuse 11 should show exactly 12.5v
And Yellow wire at cluster should show exactly 12.5v
Its just wire between these test points so little resistance to cause any voltage drop
If you see 12.3v, or less, then there is an issue

So test Fuse 11 voltage first, should be exactly Battery Volts, key ON
If not then issue will be in the fuse box
Then test voltage, at cluster, unplugged connector with yellow wire voltage, should be exactly Battery Volts

If fuse 11 and yellow wire both test OK then problem is in the cluster


Volts and AMPs
If I get 10 AA batteries with 1.5volts each and then hook them up in series for 15volts
Then hook that up to starter motor would it work?
No, of course not
But NOT because of the Volts, starter only needs 12volts and I have 15volts
Its because of the AMPs, when starter is activated my 15volts would drop down to almost 0volts because there is not enough AMPs to push voltage thru the device

You are seeing the same thing, fuse 11 is 7.5amps, more than enough amps to push voltage thru a 12v bulb, so somewhere in the circuit that 7.5amps is being limited

 

I have read all your stuff, and you are awesome. I figured out my issue, it way my own doing. When I took the alternator clip apart I mied up the yellow and green wire location.