97 Explorer no tach no speedo under charging.

[Ramcharger90]

My wife sent me this earlier today. Then a video of her driving with no speedo would an alternator cause the tach and speedo to drop out? She said it wouldn't restart after she got home. I haven't had time to mess with it, but I think that alternator is less than 2 years old.

 

[SenorNoob]

If the alternator was bad and the battery voltage dropped too low, I'd expect everything to cut out at close to the same time. However, I was driving a Suzuki Vitara that had that happen. The gauges and lights went out a couple miles before the fuel pump and ignition. Battery voltage immediately after was like 6v. So it's certainly possible.

 

[Ramcharger90]

If the alternator was bad and the battery voltage dropped too low, I'd expect everything to cut out at close to the same time. However, I was driving a Suzuki Vitara that had that happen. The gauges and lights went out a couple miles before the fuel pump and ignition. Battery voltage immediately after was like 6v. So it's certainly possible.

I think I have a spare lying around but I don't know if it's any good. I just wouldn't get why it would be fine the all of a sudden happen on a short drive home.

 

[SenorNoob]

That's usually the way an alternator goes. All at once. Sometimes they discharge the battery faster than the truck does when to go. IDK where you are, but; most parts stores around here can test an alternator. O'reilly's here doesn't charge anything and usually invites me back to watch them test it.

 

[RonD]

Battery light is on so alternator voltage was less that battery voltage, that's what that light means
(Like key on, engine off)

Battery voltage is 13volts MAX, usually 12.8v to 12.3v
Alternator's MIN voltage output at idle is 13.5v, so engine running, alternator voltage will ALWAYS be higher than Battery voltage, unless alternator has failed

So all electrical systems are running off Battery voltage when Battery Light is on, it takes 30-40amps to run a vehicle's electrical system while driving

Anything electrical can/will act up as battery is drained
And Vehicle batteries are not made to be drained
They are made to supply high amps for a few cranks of the starter, then to be recharged quickly
Steady drain can kill the battery, best case shorten its life

Which is why failing alternator can take the battery with it or soon after, so heads up on that

There is an alternator fuse in engine fuse box
And in 1997 Rangers an alternator fusible link on starter relay post


I get my Ranger alternators from wrecking yards, factory ones, they tend to last longer than "new" these days
New alternators and starters just don't seem to last any more

 

[Ramcharger90]

So I replaced the alternator but it still isn't charging. And the battery light is not coming on now. I checked the voltage and it is dropping. The green wire reads the battery voltage which was at 12.55 after I charged it. The yellow wire was lower like 9 but dropping. I checked to see if the bulb was burnt out since I read it's part of the charging circuit and was working before. But it looks good. I checked all fuses. They are good. When you take either battery cables off it dies immediately. What's next? I can get a battery but I don't think that's gonna help.

 

[RonD]

Battery won't help, 12.5v is OK

Key off
Test the voltage on the B+ wire/terminal on the back of the alternator
Should be 12.5volts same as battery
If not then that wire is not connected to battery positive and should be
Usually on the starter relay's large post that has battery positive cable

Yellow wire should also be 12.5v, not 9v so bad connection there, hooks to a fuse in engine bay fuse box

Key on
Green wire should be 12.3 or 4v which is fine
There is a Resistor in the instrument cluster on the Battery Light Bulb terminals, so if the bulb ever burns out alternator would still work
Resistor has more resistance than the bulb, so the 12v flows thru the bulb to the green wire vs thru the resistor, but if the bulb burns out the 12v flows thru the resistor

This is 1997 Ranger charging diagram

 

[Ramcharger90]

So I found the problem the fusible link was broken and the yellow wire had a corrosion hole. So I would like to go with an inline fuse a guy was telling me a 30 Amp should work he was wrong it pops immediately. What should I put in place and what Amp rating for a 130amp alternator?

 

[RonD]

Well its 130amps
But truck uses 35-45 amps average when running with all electrics on

But alternators do voltage spikes which is why fusible links are used or in 1998 Ford changed to 175amp Mega Fuse

If you can't find another 12gauge Fusible link then you can get 175amp Mega Fuse in a holder

Not sure what your "in line" fuse holder is like but you might get away with a 60amp slow blow fuse for now

 

[sgtsandman]

So I found the problem the fusible link was broken and the yellow wire had a corrosion hole. So I would like to go with an inline fuse a guy was telling me a 30 Amp should work he was wrong it pops immediately. What should I put in place and what Amp rating for a 130amp alternator?

Anyway to determine what gauge the fusible link wire is? Summit sells fusible link wire as long as you can figure out what the gauge is: https://www.summitracing.com/search/part-type/fusible-links/brand/pico-wiring

I tried to look up the charging system on the 2011 for a reference, even though it has a 95 amp alternator and nothing was listed in the owner's manual. I'll grab the electronic manual for it and see if it provides any information to help.

 

[sgtsandman]

My Ranger has two fusible links. Fuse link A is 10 gauge and fuse link B is 18 gauge. Link B comes off the regulator. So link A is probably the one you are more interested in. Being that is the case, and your alternator puts out more amps, the direction Ron is pointing you to is probably where you want to go.

I've heard about people using regular wire in place of unobtainium fusible links. I believe they used the same gauge as what the link was made of but I am unsure on that. If you don't want to go that route, the mega fuse is probably the best step.

 

[RonD]

Its in the 1997 diagram, 12 gauge Fusible link, on the B+ wire

A fusible link is usually a wire size smaller than the "main" wire
So if alternators B+ was 10ga then 12ga Fusible link

The point of any fuse is it needs to blow BEFORE the wire does, i.e. "a smoke show", lol
That's why replacing a 10amp fuse that keeps blowing with a 20amp fuse is dangerous business, lol, 20amp fuse may also blow IF YOUR LUCKY, if you are not lucky the a wire, probably in a harness, will heat up, "smoke" and take a few other wires out when it finally burns out


Fusible links are made of wire and insulation that will melt and separate WITHOUT causing a fire or "smoke show"
And they are "slow blow", they will tolerate amp/volt spikes without separating which is why they are used with alternators

Fuses/fusible links need to be as close to the constant power source as practical
In this case, and most others, that will be the Battery positive power

 

[Ramcharger90]

The fusible link was two 12 gauge wires with a single ring connector on the starter solenoid. The b+ from the alternator is 10 gauge into those two 12 gauge wires.

What I found online last night on some conversion table was 12 gauge was 41 Amp limit so 2 wire 80 amps not quite sure how accurate that would be.

 

[RonD]

Two 12ga fusible links would make more sense

 

[Ramcharger90]

Two 12ga fusible links would make more sense

I used an 80 Amp midi fuse and see through holder seems to be working I turned everything on and drove it didn't pop so I think it's good now