Alternator problem

[SWE_lollo03]

Hi so i was out driving arround two weeks ago and i blew one of the oil colant hoses and it coverd the whole engine bay and everything in there including the alternator so i fixed the hose and refilled the oil and drove it home. When i got close to home it wouldn't run right i needed to give it some throtle from time to time and when i finaly got home and was going to park it died when i stoped so i tried to start it again but the battery was dead so i took it out and charged it and figured maybe the brushes in the alternator are coverd in oil or something so it wont charge. They were so i cleaned them and the rest of the engine bay and then put the battery back and started it but it still wasen't charging and now My charging lamp is on when the ignition is off but not when the car is runing, anybody know what's going on with it?

 

[RonD]

Thats an odd one

1988 Ranger should have the 2G or 3G charging system
So one large wire on B+ terminal, stub and nut terminal

And 3 wire voltage regulator plug, for internal voltage regulator

With key off
Use volt meter to test B+ terminal, use alternators metal case as the ground(for all tests)
Should see Battery Voltage, i.e. if you test battery terminals and see 12.4v then thats what you should see at alternator
If not fusible link is blown

Unplug 3 wire connector
Test Yellow wire, should see battery voltage here as well, if not fuse or fusible link is blown

Test Light green wire, should see 0v
Turn on the key/engine off
Retest green wire, should now see battery voltage, can be 0.1 or 0.2 less

If all wires test as OK then plug 3 wire connector back in and start the engine
Test voltage at battery, should see 14+ volts, if not alternator is bad, might try disassembling and cleaning it

 

[SWE_lollo03]

The green wire was 4,5 volts so then it's probably broken right?

 

[SWE_lollo03]

I tried with another alternator and it shows the same

 

[Eddo Rogue]

Unless you had the bad luck of getting a bad alternator out of the box, you may have a legit wiring issue.
It could be something as simple as a plug connection, or complicated like a computer issue. I would assemble a photographic chart of your electrical system, and isolate the charging system. From there I would reference it to check all connections, grounds and point along the wiring that is exposed, and could be worn or damaged. If everything is good with charging, move on to the computer parts/wiring diagram.

 

[SWE_lollo03]

Yea no i found the problem just now the battery is broken but still shows 12.5 isch volt but wont charge unless it's from a charger and not the alternator

 

[RonD]

If key was on the green wire should be 12volts, this is the ON/OFF switch for alternator, 4.5v wouldn't turn alternator on

The green wire comes from the instrument cluster, the battery light
When you turn on the key the battery light bulb gets 12v from ignition switch
That 12v goes thru the bulb and out the green wire to alternator, since alternator is OFF the Battery light bulb comes on, alternator "acts" as a lower voltage(ground) for the bulb, so it lights up

When you start the engine the 12v on green wire is the "startup" voltage so alternator can start making its own voltage
When it does then the green wire has its own 12v so battery light goes off

With 4.5v on green wire the alternator can NOT "start up" to make its own voltage so no charging, alternator is OFF

Most likely the wire is not broken but has corrosion on a connector between alternator and instrument cluster
I would start unplugging any connectors you can see/find in the engine bay and look for corrosion