'98 EB Alternator Probs & Replacement

[Mike789]

I don't see a Useful Thread for this, so...
My '98 EB isn't charging. I could swap batteries from one car to another once/week, and then let the other car (VW) charge the battery, swap back, etc...but this might be more of a PITA long term.
What tells the alternator to charge ? Hopefully not the GEM as mine is about DOA. Does this year have a built-in regulator in the alternator ? I'm used to old cars that have separate regulators.
Anyone swapped a 98 alternator on the 4.0 engine ?
I looked at the area and, do I have to take the water hose off too or just the air stuff above ?
Does anyone rebuild them, like the good ole days ?

 

[imp]

I don't see a Useful Thread for this, so...
My '98 EB isn't charging. I could swap batteries from one car to another once/week, and then let the other car (VW) charge the battery, swap back, etc...but this might be more of a PITA long term.
What tells the alternator to charge ? Hopefully not the GEM as mine is about DOA. Does this year have a built-in regulator in the alternator ? I'm used to old cars that have separate regulators.
Anyone swapped a 98 alternator on the 4.0 engine ?
I looked at the area and, do I have to take the water hose off too or just the air stuff above ?
Does anyone rebuild them, like the good ole days ?

Specific to the year, I cannot tell you much. However, the alternator in any vehicle is "told" to charge by the state of charge of the battery as well as the electrical load imposed while running. IOW, the battery has ONLY ONE main purpose: to start the engine. (Yes, in today's vehicles, it also supplies very small power to "keep alive" certain accessories).

From the beginning, then: the battery provides power to start the engine. That power is quickly returned to the battery by the alternator, recharging the battery, after which the battery does essentially nothing until the next starting routine. Once the engine is running, and the energy used for starting returned to the battery, ALL ELECTRICAL POWER used by the vehicle, lights, ignition, A/C, etc., is SUPPLIED BY THE ALTERNATOR, not the battery. If the alternator works only weakly, or not at all, that power will be supplied instead by the battery (if it's capable), thus draining it of charge.

Hardly any cars now have external or separate voltage regulators.

 

[RickOTR]

Sounds like the brushes and slip ring have reached there end of life and need replaced. I've rebuilt a few of the 4G alternators with new slip rings, brushes and bearings but it takes some expertise. Note that the slip ring is polarity sensitive so if you get it on wrong you'll have to take it off which will destroy the slip ring and will need replaced with another new one. Here is what most people have used here on the forums and has worked well for them.

4GM - Alternator Starter Rebuild Kits

Have doubts about rebuilding your alternator? Not sure if your alternator is bad? Check out some important tips from the PROS!!! At rebuilderinabox, NOTHING is more important than quality assurance. For decades, we have dedicated ourselves to the the acquisition of superior quality starter and...

alternatorstarterrebuildkits.com

Edit: you don't have to disconnect the radiator hose even if it runs over the alternator. Just remove the three bolts holding it down and the nut to the battery cable on top, then the wiring that goes to the alternator then slid it down after removing the serpentine belt. Very easy...

 

[Mike789]

Thx for the replies and info...I just called Advance, and they have the 95A for $116 and the 130A for $160. WOW. Gone are the days of the $35 alternator (I'm over 60). Been a while since I had to buy one. As a side note, I drove it for 2 weeks, only a few nites, used the heat too, with no charging at all. I can't imagine using more than 10A for the heat and lites together, but...maybe I will wait on this until the weather is better, and just swap batts from one car to another every week.
I could check to see if anyone can rebuild this locally, but if the parts are $60, I'm at the cost of the 95A model already.
Is there a way to 'hot-wire' an alternator so it charges as I see fit ? I once did this 40 years ago on a Mercedes, but bought a regulator eventually.

 

[XLTrunner]

I've found that it's not unusual at all to find a newer replacement alternator on an Explorer at my local U Pull. They charge $28. Worth taking a look if you have any JY's in your area. They are one of the easiest alternators to remove.

 

[imp]

Thx for the replies and info...I just called Advance, and they have the 95A for $116 and the 130A for $160. WOW. Gone are the days of the $35 alternator (I'm over 60). Been a while since I had to buy one. As a side note, I drove it for 2 weeks, only a few nites, used the heat too, with no charging at all. I can't imagine using more than 10A for the heat and lites together, but...maybe I will wait on this until the weather is better, and just swap batts from one car to another every week.
I could check to see if anyone can rebuild this locally, but if the parts are $60, I'm at the cost of the 95A model already.
Is there a way to 'hot-wire' an alternator so it charges as I see fit ? I once did this 40 years ago on a Mercedes, but bought a regulator eventually.

Only rebuilding possible is replacement of bearings, brushes and diode bank. Voltage regulator not usually reworkable, but may be in some models. Generally, most common cause of failure is front bearing or brushes. Bad bearings make noise, squeal like hell, worn brushes can cause reduced output, not total failure to charge, harder to pinpoint. Diode failure often results in short circuit, or open circuit, making for additional checking necessary of fuse links, etc.

 

[Mike789]

Only rebuilding possible is replacement of bearings, brushes and diode bank. Voltage regulator not usually reworkable, but may be in some models. Generally, most common cause of failure is front bearing or brushes. Bad bearings make noise, squeal like hell, worn brushes can cause reduced output, not total failure to charge, harder to pinpoint. Diode failure often results in short circuit, or open circuit, making for additional checking necessary of fuse links, etc.

Thx. My Dad and I rebuilt a few alternators in the 70's, but no more it seems. I will stick to the JY or Advance, not sure yet.

Is there any way to tell which model alternator I have ? 95A or 130A w/o taking it out ?

 

[RickOTR]

The "Rebuilder in a Box" is a great kit and makes rebuil of the 4G a breeze. It comes with the stator, regulator, and high speed bearings. There are several people on the forum who've rebuilt this alternator so take a look and see if it's something you can do. Diodes and regulator rarely go out on the rectifier as the 4G is bulletproof. Yours is the 130 amp.

 

[donalds]

How to: - 4g alternator rebuild with pictures

So about a year ago I bought a remanufactured alternator From autocrap Since then the bearings went out twice making lots of noise So instead of changing it again for warranty I figured I may as well rebuild it the correct way and make a how to thread

www.explorerforum.com

 

[Mbrooks420]

Thx for the replies and info...I just called Advance, and they have the 95A for $116 and the 130A for $160. WOW. Gone are the days of the $35 alternator (I'm over 60). Been a while since I had to buy one. As a side note, I drove it for 2 weeks, only a few nites, used the heat too, with no charging at all. I can't imagine using more than 10A for the heat and lites together, but...maybe I will wait on this until the weather is better, and just swap batts from one car to another every week.
I could check to see if anyone can rebuild this locally, but if the parts are $60, I'm at the cost of the 95A model already.
Is there a way to 'hot-wire' an alternator so it charges as I see fit ? I once did this 40 years ago on a Mercedes, but bought a regulator eventually.

You didn’t. The alternator is charging some. With no alternator your battery would die in a few miles, max. Your injectors and ignition use tons of juice. Your alt is weak, not dead.

Having yours rebuilt locally is a solid option. Remanned alternators are a crap shoot.

 

[CDW6212R]

FYI, you need to identify which 4.0 Engine you have, each takes a different alternator. The OHV 4.0 takes a 3G unit, which swaps back to the 91 Explorer(same 3G). The SOHC 4.0 V6 uses a 4G unit, the same as the 302 uses from 96-01.

If it isn't a rare low option model, it likely needs the 130amp unit. Check and clean the battery posts well, those can be a cause of many electrical issues.

 

[Mike789]

Good stuff to know. I didn't realize the engine would use so much. Didn't someone post that the only thing the batt does is start the car ? I'm pretty sure the Exp has a SOHC 4.0, but I am not 100% sure as the eng was replaced approx 5 years ago.

I should back up. What happened is that after sitting for a year, I drove the Exp for 2 weeks, using heat, lites a few times. After 2 weeks, while driving with the lites on, the car started to die, as it wouldn't run with the lites on. That trip back home was very interesting but w/o any blue lites !

I haven't checked it with my own volt meter, but will soon. Should I expect about 15v when running at 2000rpm ? I already took the corroded terminals off and cleaned them. I didn't do this b4 as if it started I figured it was only external build-up.

 

[CDW6212R]

The voltage at idle will be close to 14.5 if nothing is really running but the engine, maybe under 14 if lots of stuff is on.

Here's my 93 OHV, and 99 SOHC engine, you can tell the difference for yours by this.

 

[Mbrooks420]

Good stuff to know. I didn't realize the engine would use so much. Didn't someone post that the only thing the batt does is start the car ? I'm pretty sure the Exp has a SOHC 4.0, but I am not 100% sure as the eng was replaced approx 5 years ago.

I should back up. What happened is that after sitting for a year, I drove the Exp for 2 weeks, using heat, lites a few times. After 2 weeks, while driving with the lites on, the car started to die, as it wouldn't run with the lites on. That trip back home was very interesting but w/o any blue lites !

I haven't checked it with my own volt meter, but will soon. Should I expect about 15v when running at 2000rpm ? I already took the corroded terminals off and cleaned them. I didn't do this b4 as if it started I figured it was only external build-up.

A battery does a lot more than start the car. It allows an alternator to underproduce amperage at times when the momentary load exceeds what the alternator is capable of putting out.

 

[Mike789]

I figured as much, in that a battery acts like a capacitor.

If I disconnect the + from the batt, will the Exp still run ? If it runs does this mean the alt is putting out some juice at least ?

 

[Mbrooks420]

Don’t disconnect the battery when running. It’ll arc, and you can damage the regulator. Check the voltage running vs sitting with the engine off for 30 minutes. If the voltage increases running the alternator is functioning, at least partially. Should have a little over 12.5v sitting and 14.5ish running. You can also turn on the defroster, heat, and high beams and test voltage again. If it can’t keep the voltage substantially higher than 12.5 with any load you can add the alternator is likely bad. (Or you have a connection issue)

An auto store can do a load test on it to test if it has a diminished capacity.

 

[imp]

A battery does a lot more than start the car. It allows an alternator to underproduce amperage at times when the momentary load exceeds what the alternator is capable of putting out.

I never expected this degree of misunderstanding and misquoting over something as simple as two batteries connected together, which is exactly what the alternator-battery combination is. The only difference is that the alternator is capable of providing a range of voltages, while a battery is not. Stop considering amperage long enough to understand that VOLTAGE causes AMPERAGE, which is the AMOUNT of current flowing. Underproducing amperage is a phrase I've never before heard in 70 years of working on electrical systems!

It's simply this: IF the battery is incapable of producing a high enough voltage to keep things running, the alternator raises the system voltage to the needed level. This means that so long as the DEMAND for power does not exceed the alternator's ability, NO CURRENT WILL BE PROVIDED BY THE BATTERY. Some current will flow BACK INTO THE BATTERY whenever it's voltage is lower than adequate, such as after starting the engine, or when the battery is failing. Here is what an alternator-battery combination looks like:

Note that battery + MUST connect to alternator +, and - to -. This means they are in parallel with each other, an electrical load connected to either + and - will DRAW CURRENT from BOTH battery and alternator, if their voltages are equal, more from one or the other whose voltage is higher. Battery output voltage is pretty constant, but the voltage regulator can ADJUST alternator voltage such that alternator voltage is ALWAYS slightly higher than battery voltage. That causes current to flow INTO the battery instead of OUT OF IT, the process is called "charging".

Yes, the battery can be disconnected if the engine is running and all power needed is supplied by the alternator. NOT a good idea with today's car's because they have sophisticated circuitry damageable by alternator voltages not consistent with a battery being present in the circuit.

 

[Mbrooks420]

I never expected this degree of misunderstanding and misquoting over something as simple as two batteries connected together, which is exactly what the alternator-battery combination is. The only difference is that the alternator is capable of providing a range of voltages, while a battery is not. Stop considering amperage long enough to understand that VOLTAGE causes AMPERAGE, which is the AMOUNT of current flowing. Underproducing amperage is a phrase I've never before heard in 70 years of working on electrical systems!

It's simply this: IF the battery is incapable of producing a high enough voltage to keep things running, the alternator raises the system voltage to the needed level. This means that so long as the DEMAND for power does not exceed the alternator's ability, NO CURRENT WILL BE PROVIDED BY THE BATTERY. Some current will flow BACK INTO THE BATTERY whenever it's voltage is lower than adequate, such as after starting the engine, or when the battery is failing. Here is what an alternator-battery combination looks like:

View attachment 325015
Note that battery + MUST connect to alternator +, and - to -. This means they are in parallel with each other, an electrical load connected to either + and - will DRAW CURRENT from BOTH battery and alternator, if their voltages are equal, more from one or the other whose voltage is higher. Battery output voltage is pretty constant, but the voltage regulator can ADJUST alternator voltage such that alternator voltage is ALWAYS slightly higher than battery voltage. That causes current to flow INTO the battery instead of OUT OF IT, the process is called "charging".

Yes, the battery can be disconnected if the engine is running and all power needed is supplied by the alternator. NOT a good idea with today's car's because they have sophisticated circuitry damageable by alternator voltages not consistent with a battery being present in the circuit.

I was just simplifying a concept. I saw no need to muddy the waters further with lots of technical detail.
If you want to get technical it’s a three phase motor, a regulator/rectifier and a battery.

 

[imp]

I was just simplifying a concept. I saw no need to muddy the waters further with lots of technical detail.
If you want to get technical it’s a three phase motor, a regulator/rectifier and a battery.

Ok, OK! But simplifying technical concepts has often led to more confusion, at least for me. I've always felt the user of electrical components (Mechanic of vehicles) often lacks basic understanding of: necessity of a complete circuit, voltage as a FORCE causing electric current to flow, heating effects throughout explaining need and operation of fuses..........use as an example the question "if I disconnect the battery +, can the alternator still put out a tiny amount of juice"?

But where to draw a line between technical info and practical applied ability? I dunno. Do you?

 

[donalds]

Ok, OK! But simplifying technical concepts has often led to more confusion, at least for me. I've always felt the user of electrical components (Mechanic of vehicles) often lacks basic understanding of: necessity of a complete circuit, voltage as a FORCE causing electric current to flow, heating effects throughout explaining need and operation of fuses..........use as an example the question "if I disconnect the battery +, can the alternator still put out a tiny amount of juice"?

But where to draw a line between technical info and practical applied ability? I dunno. Do you?

You might want to check out YouTube channel. AVE
It's good