1994 Ford ranger 4.slow. I noticed my alternator making a noise when a diode fails. Replaced it with a 130 amp alt due to the fact I sadly have to let the truck idle at work. (Oilfields) my job requires me to be on location so I play on my PS4 and run a 400 watt inverter. Anyways it was making the noise before I installed my inverter. Battery is new as old alternator was failing or so I thought ? Die to the fact the battery died. Replaced the battery and alternator. Still same ****. .. wines like a supercharger lol. Grounds look fine . Nothing off. Anybody have any suggestions.i seriously doubt bad part ! I mean if the old alternator made the same exact noise as if it were working hard then j doubt the alt is defective. Not a belt slip not a bearing it's definitely working hard. The question is why ? . The battery is fine. 13.9 volts when driving around. What the hell is the problem...this truck has been a nightmare. 3 transmissions I hate the a4ld pile of ****. Got so good at pulling the transmission I can do it in 4 hours. ..this trucks been horrible. Cracked head bad valve seats 2 piece Shitshow drive shaft I converted to a 1 piece .lots of problems. it also has down syndrome when letting off the gas lol. It literally makes a "derp derp derp" sound as if it's engine braking and kicking down searching for gears. Yet the solenoids are fine...kick down cable is fine. God this truck blows

 

A4LD is a good transmission if rebuilt correctly, if not then it will only last a year or so
Good read here on that: Ford Ranger A4LD Automatic Transmission

An alternator only outputs maybe 1/2 its AMPs when engine is under 1,000RPMs, engine needs to be at approx. 1,800rpms to get full power from an alternator.
400watts at 12vDC is 34AMPs

Factory alternators put out vehicles max usage at idle, so head lights should NEVER dim at idle, lol.

1994 Ranger should have had a 95amp alternator, so vehicle max draw would be 40amps at idle


Alternator has 3 Field coils in its case, they are what use the Diodes inside.
If a diode fails then alternator output is cut by 1/3, you lose that Field

On start up battery needs to be recharged, so voltage regulator in the alternator will crank up the voltage to 14.5-14.9volts
This should only last a few minutes, then voltage will drop to 13.5-13.8v regardless of what electrical power is being drawn, as long as it is less amps than alternator can produce at engine RPMs.

If you draw too many amps then you will burn out alternators

If you use too small a wire on B+(main power wire on back of alternator) then you will burn out alternator.
If alternator/engine ground wire is too small then it will burn out alternator

Howling noise could mean you are drawing too many amps at that RPM, so failed field or under powered alternator.
Back in the old days you would install a manual throttle to hold RPMs high when sitting, and using PTO or electrical power

Running 4.0l engine just to get 400watts of power seems a little wasteful in gasoline and engine wear and tear
Have you looked for a new or used small generator

 

No I'm not interested in a generator. I get free fuel thanks for the alternator info. I didn't know that. The engine is being replaced eventually with a 3.8 SC I've built. The ranger has other projects in mind. 4r70w swap with an adapter for the 1356. A4ld trans are garbage ..they will not hold **** for power. This is widely know. Anyways. I know I'm pulling 35 amps. What I don't know is why the alternator is screaming. Battery if fine alternator is new .no ground problems that I can find. I guess what I'm going to to do next is check for continuity and resistance of the grounds with my meter. Just curious if anyone has ran into this issue before? . This is annoying. Also fixed the down syndrome on the truck. Kick down cable attachment was worn out and wasn't holding the cable in place...now my truck sounds like it has a normal IQ lol. But still this damn alternator is pissing me off.

 

You are drawing 70+ AMPs......at idle
Inverter is 35amps and running truck is 35amps
130amp alternator would be MAXed out at 65amps at idle, so it would be making a noise

A car Battery is at most 12.9volts
Alternators run minimum 13.5volts, so battery is not used for "power" once truck is running.
So battery condition only matters for starting engine.
After that it's all alternator power

Your best solution would of course be a portable generator since it can be used any where and in any vehicle with any electrical devices.
But thats out

So you will need to get 2nd battery and an Isolator(basically a older ford starter relay)
400 watt Inverter hooks to 2nd battery, so get at least 1600watt(140amp) Deep Cycle battery, that will provide 4 hours at 400watts
2nd battery is grounded to vehicle but its positive cable runs to the high amp relay, and other side of relay runs to B+ on alternator, with 75 amp inline fuse
You have a switch on the dash to close the relay but ONLY when driving with engine above 2,000rpm, and that will re-charge the 2nd battery

Manual throttle control, twist lock cable, raise RPMs to 1,800 while using inverter

200amp alternator might work but they can be finicky, and might just stall the engine, lol, probably not, anyway those are the options

 

The alternator makes the noise when I'm not even using the inverter. The inverter is off and disconnected. I have a high idle on my truck so it's at 900 rpm when I idle to prevent oil deprivation and glazing. Yes gas engines can glaze I worked as a diesel mechanic and auto mechanic for a few years. Thi alternator issue has me stumped. As I have checked it for continuity and checked all wires. Solid. Yet I can tell the alternator is working hard. And nothing is pulling current. Batter doesn't go dead overnight. No hard start. Voltage is Normal. But the alternator is screaming ...can't figure this out. Wtf.

 

Well I did a check again and now it's 16.6 volts at the battery when running. overcharging hard as ****. Did a continuity test again. And still no ground issues. Did a volt drop test positive and negative and nothing..did a fuse test for a short.. nothing..I'm wondering if it's the ecu now ?

 

I would say the new alternator is faulty.
The ECU doesn't control the alternator.

Another guy here went through at least 2 or 3 new alternators before he got a good one.

 

Yes, bad alternator/voltage regulator

An Alternator is limited to 15volts DC max so you do have a problem
Alternators generate higher AC Voltage, the Diodes inside convert that to lower DC Voltage, so AC Voltage is probably "leaking" thru an internal circuit causing the 16volts
Old style Generators in cars produced DC voltage directly, the switch to "Alternators", named for alternating current(AC), is a more efficient way to generate electricity

As Jeff said the alternator/voltage regulator is a self contained system, there is no outside control over voltage output, so not an ECU/computer issue

Test volt meter to be sure it is correct, but sure reads like alternator needs replacing

But you still need to deal with the AMP overload at idle with a 130amp alternator, 900rpms will produce 65amps if 130amp alternator is working "perfectly"

Test alternator wiring first.
B+ wire(back of alternator) should have 12volts(battery voltage) when key is on or off, it is rated for 95 amps only, 1994 stock alternator, you should add another wire and Fusible link, for optimum amps, but your call, this isn't part of current problem

Unplug the 3 wire connector on alternator(voltage regulator)
Yellow wire should have 12volts key on or off
Light Green wire should be 0 volts key off, 12volts key on........this is the Battery Light circuit, also the ON/OFF switch for alternator

White wire is a short jumper, it connects voltage regulator to "alternator" so wire needs to be in good condition, no fraying at connectors, and good clean contacts

If wiring all reads correct voltage then vehicle system is OK, alternator is the problem, regardless of any "parts store" testing or new status

After new alternator is installed start engine
Test battery voltage, should be 14.5-14.9v

Let it idle for a few minutes and voltage should drop to under 14volts, re-charge cycle for battery is complete
If battery voltage is now 13.7, for example, turn on headlights and fan to HIGH, voltage at battery should drop then come back up to 13.7v, thats the voltage regulator responding to AMP draw and turning up output AMPs to get back to 13.7v
Turn off head lights and Fan
Voltage should go up a bit then drop back to 13.7v, as voltage regulator lowers AMPs that are no longer required

Now test with inverter, turn on equipment and see what voltage regulator does, voltage should drop and then come back up to 13.7v, if voltage can't get back up to 13.7v then you are drawing more AMPs than alternator can provide at idle RPMs
Raise RPMs until voltage is back up to 13.7v, thats the idle level required
Also turn on lights or any other electrical devices that might be used while inverter is being used, to get correct AMP usage required for the situation

 

I really don't think the alternator is bad. I thought that on the ecu it also helps regulate voltage when ecu detects draw? Also I've noticed on my volt drop test the engine is hot. 1.2 volts on the negative or ground side.yet I tested the chassis ground . 0.002 perfect. Could the bracket not be getting a good contact to the engine causing it to get a weak ground? Also I did the voltage test again lol . This time it's consistent temp is 66 degrees outside and not cold. It's 15.5 volts pumping out of the alt and battery voltage is 13.8 key off underload the voltage is 15.5 volts. Yellow wire from the voltage regulator is 13.5 volts . Green is zero and ground is 00.2 volts... I did a complete look over on all my wires nothing is broken nothing is cracked . So you guys are telling me that the ecu won't cause it to regulate more voltage ? I find it very hard to believe it's the alternator. It's doing the exact same thing as the old unit. I'm not going to just replace it again and hope for the best. I'm going to pull the regulator off and install the old one and test it. I think it's something else. Like a shitty ground or a hot wire touching the block or something stupid like that. Yet I can't find it. ...the engine is hot though. 1.2 volts is over the limit. I guess I'm going to take the bracket off and clean the contact surfaces on the block .***** dirty and covered in oil and grime. 210 k miles. The positive is when I replaced a cracked head the cylinders has factory cross hatch marks. Pays to use premium oil lol I use delo diesel oil and bg moa since 148k . Still has perfect compression. Just wish this truck would stop being an *** hole!


Also should have noted that my dash has serious issues. Like my oil pressure will be just fine...then jumps high then low randomly. It doesn't fluctuate fast it's more like I can drive for 2 hours before some changes .I test oil pressure with my gauge. Has 18 at idle and 60 at 2500 rpm. So I know pressure is fine. It doesn't fluctuate. Also temps jump and go down like no other. Yet the coolant temp is 190 to 200 . Think it's just a resistance problem or again some fucked up ground. Could I ground a bracket to the frame then frame to the battery to check if it's a bad ground somewhere that I haven't looked ??

 

Your volt meter is off, as long as you know by how much it should be OK
Reads like it is .6volts high, assuming new battery

Making alternator output just after start up as 14.9volts
Battery voltage, engine off, 12.9volts

Car batteries have 6 Cells inside, each cell should have 2.15 volts when battery is new
6 x 2.15 = 12.9volts
After a few years each cell will be 2.1volts so 12.6volt battery
At end of life, 5 to 6 years, each cell will be close to 2volts, so 12.0-12.2volts, time for new battery

Most older batteries that are "just dead" one day, have a shorted cell, its at 1volt or lower and sucks energy from the other 5 cells that are at 2volts, so battery drains itself, even if not connected to vehicle
You can test each cell in a battery by removing the cap and then put volt meter probe in the liquid and touch other probe to + or - terminal on battery, if you got 6.3 volts then you 3 cells away from that terminal, 2.1 + 2.1 + 2.1 = 6.3

Not sure what you mean on your Ground test
If negative battery cable is connected then from there to Alternators case should be 0 OHMS

The 14.9volt just after start up should drop to under 14volts after a few minutes or battery will "cook", chemicals inside the wet cell battery will boil away

Ford did try "Smart Charging" in the early 2000's using newer battery type, silver calcium battery.
read about it here: http://www.valeoservice.com/data/mas...E6E8714173.pdf
And when using silver calcium batteries you do need to run system at a higher voltage, which was the reason for "smart charging", these batteries do last longer than the 5/6 years for standard lead acid batteries, but also cost more so no real gain for end user, and with "smart charging" you just have one more thing to go wrong, lol.


But wouldn't apply to any Ford made before 2002
So 1994 would just have standard self contained alternator system

 

I give up it's for sale .****** pile of ****. New alternator new battery had them both tested multiple times and even took the battery out of my other truck even used my buddies alternator off his ranger and still ****** worthless **** sucker is still over charging ...was close to just grabbing my ak47 and dumping 9 mags into this garbage. I'm done. This Ford pile of **** has done nothing but cause me problems from the get go. I've replaced the fuel pump 02 sensors tps sensor transmission 3 times head gaskets mystery coolant problems a set of heads and now in about to replace 80$ worth of 7.62x39 never going to buy another pile of **** ranger ****** junk !!!

 

use the money from the sale of the truck for some anger management therapy.

 

Hasn't been my experience over the years but sounds like you got a real dog in that Ranger, for sure
"Good riddance to bad rubbish"

Hope your next vehicle is a good one