'89 Bronco alternator problems and I have searched [Archive] - FSB Forums

: '89 Bronco alternator problems and I have searched

08-08-2005, 03:23 PM
I'm kind of new here, but I do a lot reading and searching my problem. I have searched read the problems and got a lot of information, but I have not found enough or the right information to solve my problem.

I understand how the alternator works. I have a new alternator (checked 3 times, autozone, Local parts store and alternator shop) and it is good and working properly. I have 12.5 volts with the engine oof start the engine I have 12.1 volts running at idle. It does not increase to recommeded volt to charge. I used the a VOM to chek coming from the alternator, checked coming from the switch to th alternator (7-9 mV). I haved cleaned all the conectors to the starter solenoid, replaced the alternator harness with new connectors, the harness made with new wires and fuse wire link. I checked the volt meter. the only thing i can think that I don't see working is the battery indicator light is not working. Possibly my Problem!!! The battery cables are in good condition and I have cleaned the ends and terminals on the battery.

everyone is going to say to go to the 3G, but I had rather deal with this problem first to deal with the problem at hand.

Is there a way to bypass the switch to get the alternator charging. the engine starts and runs perfect right now.

Any help would be greatly appreciated.

Thanks in advance,

Phillip KB4I
Fairview, TN

08-08-2005, 03:38 PM
12.1 is low it should be higher. did you replace the regulator? the reason so many say goto 3G is it is cheaper in the end to do the swap than keep throwing parts at a known issue. the stock alt is not enought to handle what we need if you add anything to the system. you can junk yard a 3G for $15 and get new wires for under $20 and a mega fuse and not have issues or fix what you have and find you do not have enough power to do what you want and need to do the swap anyway.....mike

08-08-2005, 04:20 PM
What tests did they do on your alternator? I'd check my voltage regulator...

08-08-2005, 05:29 PM
Some vehicles (not sure if Bronco is one of them) have to have the charging light working. It is how the alternator does it's voltage or current sensing.

Fix the light and you may have fixed the problem.



08-08-2005, 09:29 PM
Like I said I had the alternator checked at 3 diferent places including a professional alternator shop. The alternator tested fine at all 3 places.

No offense, but the 3G is not going to work either if the regulator isn't getting activated by the switch. I may be wrong. I will eventually do the 3G

I had the same problem with a CJ-5 that I had when I put a GM one wire alternator. I simply had a wire that was wired to a switched positive wire and it charged. Seems to me that this alternator should work the same way if a positve switched wire was used to activate the alternator.

I also read somewhere in the forum were someone else had the same problem and they did the switched wire and it started charging. Plus I also read somewhere that it would not charge if the light was not lit.

Sometimes I read too much.. So that is the reason for the question. You can't learn anything if you don't ask questions. like I said I did seach the forum and will continue searching till I find my solution.

thanks to all that have made suggestions so far.

Thanks again,

Phillip KB4I

08-08-2005, 09:51 PM
Have you checked the circuit for the battery light yet?

08-08-2005, 10:02 PM
(Quote)Plus I also read somewhere that it would charge if the light was not lit. (Quote)

Sorry I didn't read it well enough.

I would double check that though.

08-08-2005, 10:10 PM
Too quick to type.. It should have read will not charge if the light is burnt or out.

I haven't checked the the light just yet. I teach school during the day and coach Boys and girls golf in the afternoons after school. sometimes I don't home before 8 in the evening and ready to check the pin holes in my eye lids.

Phillip KB4I

08-09-2005, 02:43 AM
+12 volts to the grn/red wire will bypass the charge light

08-09-2005, 11:09 AM
I'd check/change the voltage regulator. Had one go bad on a K5 once. When I checked it I had 13.4 volts so I took an alternator for a test. Alternator tested fine. Was told that it was my voltage regulator so I put my money where his mouth was. After replacement 13.6 volts and the problem was gone. I still don't know why .2 volts made that much difference but it did. That was checking at multiple places, into the VR, out of the VR, and at the battery.

08-09-2005, 11:36 AM
If it's the regulator the alternator tests should've identified it, the regulator is internal to the alternator. One other thing you haven't mentioned is did you have the battery checked? It could be going bad & not taking enough of a charge to get above the 12v you're reading. If the battery checks out good try disconnecting everything from the starter relay & reconnecting one wire at a time with the engine running to see if any of them cause the voltage to drop. This will eliminate those possibilities if nothing else.

08-09-2005, 01:26 PM
The battery was checked at the same 3 places the alternator was checked. Everything checked good. I will go back for the 3rd time and check the voltages on all the wires.

Phillip KB4I

08-09-2005, 08:57 PM
Wow, I know people in Fairview! Welcome to FSB, from Columbia.


08-09-2005, 10:17 PM
Thanks Jeff. Seems to be a great bunch here. I have been involved with other forums (CK5, southern Jeeps and others) but this group seems to be one of the friendliest and most willing to help than most. This is my first Bronco so i got lot to learn about them. I've had a S-10 Blazer 4 X 4, '83 K-5 blazer with 6.2 diesel with 6 inch lift and '73 Jeep CJ-5. I am pretty proficient in mechanics growing up a farm in Chapel Hill, Tn and then Transplanted here in '79 where I presently teach Agriculture. I don't wheel any more just trying to get a '89 Bronco together for a Daily Driver since I'm only 2 minutes from the high school. I have access to one of the 21st century automotive shops in Tennessee schools, plus I have all sorts of metal working equipment in my own shop at school where we do a lot of mechanic work with small engines and farm tractors and etc. Our basic curriculum is Horticulture but I still sneak in a lot of hands on experince in the mechnical area.

I'm getting ready to put in a slave cylinder and new clutch and pressure plate in the Bronco in a couple of weeks. I figured since I was replacing the cylinder, I might as well do a clutch install at the same time.

I plan to become a member of the Fullsize family as soon as I can my cash into the guys. I guess I am already a fullsize wannabee, hey I got a Bronco.

Thanks again for the welcome,

Phillip KB4I
Fairview, Tn

08-11-2005, 08:14 PM
Well, I still haven't fixed my problem with my alternator but I did score two 3G alternators today. I had a doctor's appointment and had about 2 hours to go back to work, Since they were going to charge me for a full day anyway, I thought I would go home a different way. I found a used car and salvage yard onwed by some Pakistanians, so I turned around went back, I asked for an alternator for a '95 mustang GT. and they had 2. I gave $20 bucks a piece for them. I still had enough time to take them to an alternator shop that I use and they both tested in good shape. I had enough time to go a friend of mines Stereo shop and he let me go through his scrap box and scored 10 feet of 1 gauge negative cable and 10 feet of positive cable coneectors and such. He said I could have what found . Big mistake. I hit some what cable lotto.

So I guess you guys talked me into the conversion.

thanks to you all,

Phillip KB4I

08-11-2005, 11:24 PM
I used to live in Franklin..but I know a bunch from fairview and chapel hill(the tractor pull has gotten outrageus hasnt it?) I need to go searching for a couple 3G's myself since my wifes Taurus has started to develope a whine in the alt and my broncos alt sucks major..


08-13-2005, 08:13 PM
Quick update On Alternator problem. I removed the alternator and replaced with a 3G today. I still don't have 12 volt power on the green and red striped wire that turns on the regulator. I did take a wire and semi-spliced into the green-red striped and hooked it to the positive post of the battery and Wallah, the alternator started charging and actually had indication on the voltage meter. So I'm still trying to figure out why I'm not getting 12 volts on the wire. It may still be that the bulb is out.

Next question. How do get the Instrument cluster out so that I can check the bulb to see if it needs replacing?

Is there a wire on the passenger side that is switched so I can keep the alternator charging when the key is on and off when the key is off?

Would it be possible to go from the fuse box from a switched circuit to go to the alternator.

I really need to get his thing going.

I forgot to mention that I did the Ghetto fab K & N FIPK also. Great information on the site

Another question. My pipes going to the filter have a wire like sping inside. I know this is probably some type support for the pipes. Do I need to remove the wire from the pipe?

Next project: Slave cylinder and Clutch. Then Electric fans.


Phillip KB4I

08-13-2005, 11:53 PM
What year is your rig Phillip?

08-14-2005, 12:03 AM
you are saying, just to be clear, that you are not getting 12v at the green/red wire when the key is on? are you checking before the regulator?

08-14-2005, 08:37 AM
It's a '89 302 with 5 speed manual no A/C.

and yes to the question before the regulator. The alternator is a 3G with internal fan and internal regulator.

08-14-2005, 10:44 AM
ok, are you wiring the 3G correctly? if its putting out 14.x you have it working and are supplying power to the correct terminal on the alt. there are three wires coming out of the 3G plug. one goes to the charge stud, one to the green/red wire and one loops back to that other little terminal on the alt. you have to energize the green red one to get power from the alt and since you have 14.x volts coming from the alt, we have to assume that you have power to the right wire. very strange. can you get any pictures?

08-14-2005, 11:30 AM
The 3G is wired correctly. I checked and double checked to make sure. The green/ red stripe comes from the ignition switch to give 12 volt power to the alternator to turn on the regulator so that it will charge. To test the alternator, I semi-spliced a wire so that I could go to the positive side of the battery.. Like I said it charges with 14.6-14.8 volts, when i pull the wire it measures the voltage in the battery at he time.

I am not getting 12 volts through the green/red stripe wire from the switch to activate the regulator in the alternator. I have traced the wire from the alternator to the fire wall and checked for continuity and there is not a problem.