1988 Ford Ranger 4x4 wiring/voltage issue.

My 1988 Ford Ranger just developed an issue causing the charge light to come on and the lights dimmed, the wipers slowed down and the turn signals began to blink slowly. I had a brand new alternator which I put on but it didn't fix anything.

How many volts are supposed to be going to the voltage regulator? My buddy's meter read 11.54 volts at the regulator. Could it be the cables causing the draw. It starts fine without even the slightest hesitation and runs fine. Just don't want to ignore it only to be left on the side of the road. Any info would be appreciated.

1988 should have internal voltage regulator(in alternator)

There should be a 3 wire connector on the back of the alternator
1 white short jumper wire
2 Yellow wire
3 Green wire

Key off
Green wire should be 0 volts

Yellow wire should have Battery Voltage, if battery has 12.4volts then yellow wire should have 12.4volts
If not then fuse or fusible link is blown

On the back of the alternator is the B+ connector, 1 or 2 larger wires connected
You don't need to disconnect these, but test for voltage, should have Battery voltage same as Yellow wire.
If not then Fuse or Fusible link is blown


Now turn key on
Green wire should now show battery voltage, only with key on.

If all test as said then start up engine, Battery should now show 14+ volts, 14.5-14.9 volts if alternator is working.

If is doesn't then replace NEW alternator, it is bad


Just FYI on the charge light
A 12 volt light bulb will light up if you give it 12volts and 0volts(ground), if you just give it 12volts then it won't, if you give it 12volts on both connections it won't, has to have a high and low volt side to light up

The green wire on alternator runs to the Charge light bulb in the dash
The other contact on the Charge light bulb is connected to ignition switch

When you turn on the key 12volts will run to the bulb and out the green wire to the alternator, if it is plugged into the alternator and alternator is not producing voltage(engine off) then it is a Low volt, so charge light lights up
When you start the engine and alternator is working then charge light has high volts on both connections so is OFF

The green wire is more than just the charge light though, it is actually the ON/OFF switch for the alternator.
An alternator would drain the battery when engine is off if it wasn't shut off.
The green wire provides "startup power" for the alternator, and shuts alternator off when voltage is cut on that wire.

If a charge light flickers it means voltage is dropping low on one side of the bulb, below battery voltage, so alternator is not producing full power

Thanks for the reply. I'll have my buddy look at it over the weekend.

My only concern is regarding the new alternator. My assumption is it is fine and so was the one I took out. I'm going to try and replace the battery terminals to see if that helps.

I've seen new starters and alternators fail right out of the box, so it is entirely possible that the new alternator is bad, but you'll have to look into the problem.

I've had some problems with bad ground wires off the negative side of the battery causing strange electrical problems. After finding that the ground wire had corroded to junk inside the insulation on one of my trucks, I made a point to replace any battery cables that even seemed like they might be a potential problem. I use brass marine terminals on the battery and crimp my own ends on welding cable. Heat shrink and dielectric grease too.


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As this should probably be in the electrical forum, I'm going to move it over there...


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New alternator might be OK, old one may have been as well

Could just be a blown fuse/fusible link

In '88 ford still used the Starter Relay on the fender, often call start solenoid, as the Power Distribution point.

So battery positive cable will run to Starter Relay post, and on that same post will be 4 to 6 other wires that feed 12volts to the truck systems
At least one will be from Alternators B+ terminal(back of alternator) it will usually use a Fusible Link in '88
Fusible link is a shorter smaller gauge wire that will melt and separate if too many AMPs are passed thru it, so is a fuse
Starter Relay Post------(fusible link)-------(crimp splice)B+ wire-----------B+ terminal on alternator

There will be the same set up for the Yellow alternator wire, but this may use an inline fuse or Fusible link.

So both of these wires are connected directly to the battery's Positive terminal via the starter relay post, which is why they should show 12volts 24/7, all the time
Make sure to clean these wire ends on this post, unhook Negative battery terminal first, these pass power so can build up corrosion between eye rings.

If either fuse/fusible link is blown then no alternator

Also the White jumper wire can get frayed at connectors so check that it is good

Well the truck died on me when I pulled it into the driveway after picking up my son from school. It has definitely killed the battery.

I see the links you are referring to. They look to be connected to the wire on both ends. Is there a way to take them apart and visually inspect the condition? My buddy can't get to my place until the weekend. I'm going to shoot a pic or two of where I see the wires/links coming off of the starter selanoid.

You need a volt meter or 12volt test light to test for voltage, visual inspection is OK if wire is bad but won't tell you if wire is good

You may not have killed battery, just ran voltage down, get it on a charger as soon as possible or it will be "killed"
Car battery's can not sit discharged or they will go bad.

If you have another car and jumper cables then pull battery out of the ranger or disconnected BOTH battery cables, and start other car then put jumper cables on Ranger battery, charge it for at least 10 minutes, that should be good enough.

Here's a few pics of the wiring going into the selanoid and battery terminals. Are those three the fusible links you are referring to?

The Black/orange stripe wire in first pic looks like color of B+ wire on alternator?
But would expect that to have Green fusible link

here is a mustang diagram which will be similar: http://www.stangnet.com/mustang-forums/attachments/87-93-5-0-mustang-fuse-links-gif.64326/

My eyes!!! Some hideous wiring there...

If you live near a Harbor Freight, you can usually pick up a multi-meter for like 5 bucks. It's nothing impressive, but it works fine for checking voltage and tracing wiring.

Don't suppose you live anywhere near western Pennsylvania? Lol


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Remove and replace all none sealed butt connectors. Replace them with bare butt connectors and shrink tube. Most of your voltage loss could be coming from those connections.


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Look for the Yellow wire on 3 wire connector on alternator, follow it from alternator back to starter relay, it is often connected with Black/orange stripe wire to the fusible link.
And I don't see it in your pictures

If that has broken off then no power from alternator

lil_Blue_Ford said:

Don't suppose you live anywhere near western Pennsylvania? Lol

Click to expand...

Sorry, but I'm a east coast Philly resident.

I can say the wiring was not my doing. I inherited this rig from my father in law who got it from the original owner. It's in decent shape and stock except from the crappie wiring.

I've seen a lot of bad wiring on older trucks. I had one that one of the smaller ground wires was "spliced" in 4-5 places. I use quotes because the splice was to bare the wire, lay it side by side and wrap it tightly with tape. Which meant that the engine would cut out with every bump, lol.

I thought if you happened to be close enough, I'd do what I could to help with wiring fixes.


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