Draw from somewhere...

[C-Bear]

Hey everyone! I got a '98 Ranger, 3.0, 2WD, manual transmission. I've had this truck almost a year now and in the past couple months it hasn't been doing to hot.

I've got an electric short somewhere and I'm trying to figure out where it's coming from. The battery reads in at 11.8 volts while the engine is running. I've had the alternator tested at two different shops and they both said that it is good as new.

The problems I'm having are I can't have the lights on, without the truck dying. It won't die right away but you can watch the volt meter just slowly drops down. Along with that whenever I turn my marker lights or headlights on, the interior lights also turn on. Since this has all started happening, the airbag light has also been on. I've read that the light will flash when theirs an error code, however on mine it doesn't blink at all.

I'm wondering where these would all tie together, if their would maybe be a short their. I would assume it would be somewhere up front, since he corners and headlights are obviously their, maybe an airbag sensor as well?

Let me know what you guys think I've torn a lot of stuff apart already only to find no luck. If maybe theirs some kind of relay or something that went out or maybe it's completely different. Let me know!

 

[RonD]

When engine is running, minimum battery voltage should be 13.5volts, so either check your volt meter or check your alternator wiring.
If meter is correct then under 12volts means alternator is not turned on or its wires are not connected, assuming you trust the shops that checked alternator.
No short could cause that kind of voltage drop without frying the wiring.

And turning on the head lights would just drop the voltage more and engine would start to misfire and stall


Whats is the battery voltage with Key OFF?
Should be 12.2-12.8volts
12.8v is a new battery, 100%
12.2v is a 5 year old battery at 60%, and time to shop for battery sale

So once you know your battery voltage with key off, it is time to test alternator wiring.

Key still off
On the back of the alternator is the "B+" terminal, it has a larger wire, maybe 2, put volt meter on this terminal/wires and the battery Negative terminal, it should read EXACTLY the same as Battery voltage.
If not look in engine fuse box, there will be 2 60amp fuses, both are blown

If you have good battery voltage on B+ then remove 3 wire connecter on alternator
Test voltage on Yellow wire(meter still on battery negative), again it should have battery voltage, if not 1 of the above 60amp fuses is blown.

Next, turn on the key
test voltage on Light green wire, on the 3 wire connecter, should have battery voltage, this wire is the ON/OFF switch for alternator.

If no voltage on this wire then problem will be in the dash board, battery light circuit.

Drawing here: http://www.therangerstation.com/tech_library/EDiagrams/files/Diagram_charging_1991_2.JPG

If all the fuses are good and all the voltages check out, then start the engine.
Just after starting battery voltage should be well above 14volts, under 15volts but in the high 14's is normal.
After a few minutes of recharging the battery from starter motor draining it, voltage will start to drop.
It will end up at 13.6volts, this is called a "maintenance charge", about 1volt above battery voltage(key off)

If you turn on the head lights and heater fan to high, voltage should drop and then come back up to 13.6volts, thats the voltage regulator in the alternator working as it should.

 

[Earl43P]

G103 is common to some of those,
main light switch
LF park/turn/marker lights
turn signal flasher
AC clutch coil
Ground 103 is located on the DS inner fender, outboard of the front edge of the Underhood fusebox.

I'd go ahead and brighten up all your grounds,

G100/G101 right in front of the battery
G104 radiator support
G105, PS inner fender outboard of the blower motor
G102, center of the firewall, next to PCM
G201 passenger cab outboard kick panel
G200 DS parking brake fusebox area

When you clean up grounds in a Ford body panel, there are only 3 raised dimples in the metal that contact the ring terminal. No need to sand all around the hole, just brighten up those raised dimples and of course the ring terminals.

Does your BATT dash light prove out when the key is turned on?
Airbag lamp shares fuse 15 power with the Charge Indicator lamp (dash lights), the restraints control module provides the ground to turn on the Airbag lamp, the alternator provides the ground for the BATT lamp. page 60-4

Do a thorough visual inspection with a mirror and a bright flashlight of all the heavy gage +/- wiring to the battery/alternator/starter along with harness runs looking for chafes, evidence of overheating, etc. Check every fuse by touching the meter - lead to chassis ground and the red lead to the tiny electrical contacts atop each fuse while they are still installed. Each fuse has two touch points, both should have 12v or the fuse is blown (Key in Run). You might also disconnect, clean and reconnect as many relevant connections as you can get to, even at the GEM (behind the radio surround) and under the dash. Dielectric grease on the connector plastic body (not the contacts) makes them mate easier. Each disconnect/reconnect scrubs the contacts cleaner so do each a few times. Might get lucky!

Report back and I'll keep thinking about it.

Lastly, I can send you much of the 2000 EVTM (book of schematics) if you send me a PM with your email address, I'll email that 9 Meg file to you. 98 should be right close if not identical to 2000, electrically. You WANT this file.