Voltage guage low, battery/alternator NEW

[rfl]

I have read a bunch of posts on this topic. Some seem to discuss specific things that may or may not be related to a '93 Ranger (like a fuseable link off the engine compartment fuse box?) so I am posting in hopes that someone can narrow down the troubleshooting to this year truck.

The issue...

Alternator bearing let go, replaced with with a new from Oreilly - before someone piles on, it was either Oreilly or Autozone. This was a parking lot swap at my sons school. Simply nothing else available other than non-Motorcraft remans from the same 2 locations. When replacing the alternator, we also threw in a new idler since it was already known to be low on resistance. Belt is new. Truck fired right up.

Next day truck fires up in the morning, but battery is dead later in the day. Thought it may have just had a weak charge from a week worth of short trips so charge it overnight. The truck makes it through the next day but dies on the road that night. We jump started the truck and drove it home with the lights off. Thought maybe we got a bad alternator so took it back and got a different one.

Next day starts off with a fully charged battery and second new alternator. After a short drive the gauge is dipping so we load test the battery. It is bad, so replace the battery. After replacing the battery the gauge was hanging around 10, so told my son to take it for a drive to see what it does. He went about 60 miles out with the lights on, not much change in the gauge. One the way back the gauge dips a bit more. He stopped an let it idle and it dropped even more.

All the ground connects are clean. Engine was swapped less than 1,500 miles ago and all engine harness were unwrapped, inspected, and rewrapped.

The battery terminals are new, but while it looks fine I have been a bit leery of the ground multiple wires running to the a single aftermarket terminal. Everything looks tight, but...

So where do I go from here? Does the Ranger really need 4 wires going back to the battery ground or can I run some of those to the chassis? What fuses are involved in the charging process on this thing? Bah!!!!

 

[RonD]

You need a Volt/Ohm meter to test wires.

Here is an electrical diagram of the charging system: http://www.therangerstation.com/tech_library/EDiagrams/files/Diagram_charging_1991_1.JPG

The larger wires on the Alternators B+ terminal are connected to the Battery via fuses or Fusible links.
So with engine off, set meter to 20vDC, and test battery voltage, should be 12.8v or slightly higher with new battery.
Now carefully remove the two wires on the B+ terminal, these are BAD wires to short to Ground.

Test each wire for Battery voltage, so Black probe to Ground, Red probe to one B+ wire.
If battery shows 12.8v then this wire should show 12.8v, test both wires, if one or both show 0volts then fuse or fusible link is blown on that wire.
Disconnect battery ground before looking for bad fuse.
A "fusible link" is a short smaller wire made to "burn out"(without starting a fire) if a short or higher than rated amps pass thru it.
Fusible links were used in high amp circuits because they "tolerate" temporary high amps better than fuses, higher amps can occur during recharging of dead battery.

Trace 0volt(or low volt) wire back to fuse box or Fusible link, these wires use 50amp or 60amp fuses.
Set Meter to 100 OHMS and pull a fuse to test it with meter probes on each side of the fuse you will see 0 ohms if fuse is good.
If these wires go to the Starter Relay loosen that connection and check for corrosion, disconnect Battery Ground and remove wires to clean if needed.

If you are not sure if you are checking the right wire/fuse, connect one Meter probe to the B+ wire and use the other probe to find the fuse contact that shows 0 ohms, 0 ohms means direct connection.

If both B+ wires show battery voltage then fuses are fine.

With all wires reconnected and tight, including battery, turn on key.

On the 3 wire alternator connector, test the Light Green/red stripe wire, this should show Battery voltage, i.e. 12.8v, this is the from the Voltage gauge in the dash, and is the ON/OFF switch for the alternator.

Also test the Yellow/white stripe wire, it should also have Battery voltage

 

[rfl]

Thanks, Ron. Going through your steps. Battery on my VO meter just died, so running to get a new one. Will let you know what I find.

 

[rfl]

The troubleshooting list was perfect.

I was able to eliminate the wires, gauge, alternator, battery, and fuseable link rather quickly. The wiring diagram is not the same as the '93, but no biggie.

It was the engine compartment fuse block. Fuse would not make constant contact - could wiggle it slowly and the gauge would move. Had to pull the guides out and squeeze the prongs together so it would make constant contact.

I did replace the negative battery cable in favor of a more reasonable setup than what was in the truck while I was at it.

 

[RonD]

Good work

 

[Doofy]

Great write-up RonD! I enjoy concise and logical troubleshooting help. Thanks to rfl for letting us know the problem was solved and what he found.