I have seen alot of these posts. I have a customers 1989 ford ranger and this thing has me stumped and dumbfounded. first off things that have been replaced. all battery cables pos, neg, and starter cable, alternator,and battery. her we go off to the races. I start the truck and the engine surges like a vacuum leak but there is none. I turn on the lights and there is a noticeable flicker to the lights at almost the same speed of the engine surge and the head lights are dim. I test the battery with a load tester with engine off and it comes out a little weak in the 11 volt range but still good by the book once load is off the volts come right back to 12.4. I start the truck and the volt output from the alt is 14.6 volts which is also good by my book but a little high. dash shows 9 volts on the gauge but I'm thinking the gauge is messed up. back to the lights. if I ground out the field on the alt volts rocked off my meter on my load tester guessing 18 to 19 volts but guess what flicker goes away and truck idles smooth as a babies rear side. if I take the jump lead off the field ground volts come back to 14.6 volts and flicker and surge come back. during this whole jumping the field the dash gauge for the alt volts did nothing again I think that part is not working lol. what do you guys and or girls think. please feel free to write on the post on please there are no stupid ideas other then to tell the customer to live with it lol. tomorrow I'm taking the alternator back to the store and have them test the new one to make sure its not bad FML. I'm also going to remove the gauge and look into the alternator gauge and see where that problem might be. OH I forgot to add I tested with a light tester the wires coming out of the alt and for some reason the LG/R for the volt gauge is dimmer then the output to the main power distribution box with which is the Y/W coming off the voltage reg. I can post pictures if you would like.

 

Welcome to FTE.
I see you don't have any replies yet, so Ill see if I can get things started.
Might be helpful if we knew which engine this 89 Ranger puppy has & if it's had any mods, list them too.
Have you scanned for trouble code clues & if so post All code Numbers, as they can help focus a trouble shoot.
Did the problem begin suddenly after some event, or slowly over time?
Good idea to have listed the replacement parts.
Also good idea to have the alternator bench tested. It's recommended that we inspect & test all new electrical parts before leaving the store with them. I've found bad new parts right out of the box, along with the wrong part in the box.
12.4 volts no load says the battery is between 70-80% SOC.
Make sure the battery to body, frame & engine grounds are clean, bright & tight & see how things go, along with letting us know the alternator bench test results.
Some beginning thoughts for consideration, let us know what you find..

 

If the alternator (presumably with internal regulator) and the battery both prove to be working correctly, as evidenced by testing and by testing using the correct method, and if the battery cable connections (and if applicable the engine block to frame), are unquestionably sound, then I'd start by hooking up a volt meter up to the battery terminals with the engine running and see what the voltage does while the vehicle is running. Note voltages after the battery has had an opportunity to recover from the start event. Remember, the alternator charges the battery and the battery runs the vehicle; battery (in good condition) smooths out the effects of the alternator switching on/off while the vehicle is running.

 

thank you or the reply I woke up a little late today. so to answer the first questions there is one mod the smog has been removed but that really shouldn't have anything to do to the charging system, it is a 2.9L and it looks to me like there has been some wire tracing done to the loom under the hood. I spent a day looking through it and making sure connections were good. the customer just bought the truck from sources unknown so cant help you out there. I did how ever hook my volt meter up to the the battery while running and the volts are at 14.76 and fluctuate slightly unless you rev it and then it land at a different voltage but while running it is between 14.65 and 14.80 it just depends really. there are no CEL present have my snap on 2500 "red brick of uselessness" hooked up and low and behold some one must have removed the light because there is two fricking codes "Herschel there is a little yellow engine on the dash" I already checked the engine and it s still under the hood" "well dang it Terry just remove the light then" code 23 TP/FIPL sensor out of range. I'm guessing this is the Throttle sensor out of range or throttle set too high.well I will be replacing that today and or adjusting the throttle LOL but still doesn't tell me about the flicker and a code 11 which is System checks OK Which it is not because the code 23 if before the 11 its like the truck just developed some timers. "hey look code 23 wait what did i just say, never mind code 11". The code 23 although might tell me about the surge i'm getting but more then likely not. it looks to me like every time the truck stumbles when idle the volts dip but that just could be because the speed of the engine decreases and slows the alternator down. some times when I start getting into this kind of nightmare I start over thinking things causing bad dreams and restless nights LOL. just got back from Auto Zone having the Alternator tested and it tested bad. now I don't know if it was bad when we got it or if something in the truck is making the alt go bad but I have another one ordered today and I will get it tomorrow. I had the store cal the other store that has it and had them do a double test on it to make sure it was good. so fingers crossed.

 

OK good feedback. Good find on the faulty alternator. When the replacement comes in, before you leave the store with it, be sure to have them perform another bench test while you witness All of the testing & let us know how it goes.
On the code 23, make sure the supplied reference voltage to the TPS is within range, then with your analog ohm meter measure the resistance over its full operating range to make sure all is well. resistance should change smoothly, no drop outs. If you replace the TPS, make sure to test it before leaving the store with it.

 

Ok here is where I have a hard time. if it was charging the battery does that mean that it was not putting out the amps that it was suppose to? I don't under stand this if I put on a alternator that is putting out 14.7 volts but it fails the test does that just mean that it really wasn't putting out 14.7 volts because the amps coming off the alternator were nothing? because every thing that I was taught was looking good but that is why I turned to ask for help because I'm already bald and cant afford to pull hair out of anywhere else. if there anything on the truck that can make the alternator go bad? the alternator that I removed looked to be a new alternator as well as the one that I put on it I knew was new. I just wonder if there is some thing that could be burning these alternators out. as I see it the wiring is simple two battery + or B+ wires O/LB and a BK/O these feed from the Distribution box fuse #3 and #4 both 60 amp, there is a Y/W coming from the box as well and I believe this is the exciter wire and it has power. it goes to the "A" place on the regulator. then we have the W/BK wire that is a ground or tests as a ground from the Alternator main plug to the Regulator witch is the sensing wire pin "S" . lastly there is a LG/R witch is a gauge and light wire in pin "I" on the regulator. now my concern is that by what I see in my Haynes manual the W/BK wire shouldn't be a ground it should be a power wire but being that is was on the bad alternator I don't know if it was just grounding in the case when they built or rebuilt the Alternator. there is no where online that tells me if this wire should be a ground or positive.

 

You can go here BBB Industries- Premium Alternators, Starters, Power Steering Products | TSB's & Wiring Diagrams & enter the vehicle particulars to look up wiring pictorials & TSB's.
What test did they say the alternator failed?

 

Check TSB 96-21-4, the alternator electrical connector, contacts & wiring for damage, warping, overheating, contact corrosion.

 

got the exchange alternator today put it on and went to try it. batterys dead I seam to have left the key on. so I did what any one would do threw my charger on it and an hour later green ligh means its charged holding 12.4 volts. for chits and giggles I threw my load tester on it and hit the button and boom instant 8 volts batteries is now bad. WHAT THE HELL IS UP WITH THIS STUFF. battery is 3 months old.

 

As mentioned earlier, 12.4 volts unloaded indicates the battery is between 70-80% charged BUT you might have a weak cell, so if you have removable cell caps have a look at the electrolyte level in each cell, top up as necessary & put your smart charger on a slow over night charge of say 4-6 amps, then use your hydrometer to measure Each cells specific gravity to see if all are equally charged.
If the defective replacement alternator hasn't been able to keep the battery above a 70% SOC for the last 3 months, the cells have probably sulfated & may not be recoverable to achieve full capacity.
Again, what test did they say the replacement alternator failed?
Did you witness this alternator pass all of its bench tests?

 

I did'nt read thru this whole thread, so don't know if this was mentioned, but did you check for AC ripple in the alternator output voltage? That can cause flickering lights and run a battery dead while the engine is off.

 

Well, not sure how many times that battery was run down and/or run down to the bitter end, but it is worth mentioning that every time a starting battery is ran way down and/or ran down to zero, permanent damage is done and the life of the battery is shortened. Leaving headlights lights on, key on, stereos on, it all comes with a price.

 

well it has been a while sorry guys. I put a new battery in the truck and turned out it had a dead cell. I also took the alternator I bought to the auto part store and it turned out bad. they replaced it and everything is working fine other then the Volt gauge. the dash in this is reading off and I'm guessing it is the electric motor part in the gauge cluster that is the problem. I checked the soldering joints and they are fine so I have no idea. I told the owner of the truck t hat the gauge cluster might need to be replaced but I pulled the needle off and started the truck and using the volt meter I placed the needle back on in the proper place and well that will work for right now. thank you every one for the help. but if you are having the same problem trust me even new parts fail.

 

Ok, interesting finds, fixes, feedback & to hear the customer is on the road again.

 

On the ford 2.9 engines, there is a computer ground wire on the back of the right cylinder head. If it gets corroded you will get bad fuel mileage plus several other problems.
The lights flickering is usually die to a bad engine to body ground. The lighting grounds are connected to the body. If there is no engine to body ground, the electricity has to run through the drive shaft (not a good ground) and it will cause early failure to the u-joints.
Some Alternator problems can be checked out by testing for ac voltage. The alternator puts out an ac voltage. It is the diodes that convert it to dc. When you have a leaky diode, you'll still have dc voltage but your battery my not charge correctly and your lights may flicker die to the ac current. Your DVOM set on ac should read O volts with the engine running. Test at alt and not at the battery terms.