Bad Alternator??

[Seabronc]

Have you checked the voltage at the battery with the engine running, and if so, does it show the same thing? If it shows the same thing, you probably have a bad voltage regulator on the alternator.

An additional check would be to disconnect the battery (-) after it is running and then check the voltage measuring from a good ground point to the Battery (+). That will show you the output of the alternator and take the battery out of the equation. Removing the battery (-) is safer than removing the battery (+). If you remove the battery (+) and happen to short the cable to ground it will take out your alternator.

Report back with the results.

Good luck,

 

[Seabronc]

If you end up having to change the alternator, you might want to consider a 3G upgrade. Your truck has a 2G alternator. It would require a couple of minor changes, but well worth it. You can get a 3G at a junkyard or buy a new one plus the cables from RJM http://www.rjminjectiontech.com/collections/alternators http://www.rjminjectiontech.com/collections/alternator-accessories/products/alternator-charge-cable-kit http://www.rjminjectiontech.com/collections/alternator-accessories/products/3g-alternator-harness . You also may need a new pulley http://www.rjminjectiontech.com/collections/alternator-accessories/products/pulley-6rib .

Good luck,

 

[Krafty]

one of my alternators was doing the same thing, overcharging the battery which will **** the battery quickly, you can get a new alt, get one out of a scrap yard, do the upgrade like seabronc suggested, or replace the Voltage regulator, assuming its an 89 there will be an "internal" regulator on the back of the alternator you can replace by removing the 4 screws. to install the new one you have to push the two brushes up into the regulator and insert a straight pin to hold them until you get it set into place. it makes sense when your looking at it in your hand.

good luck

 

[michael1989]

Ok so I just got my battery back fully charged and it load tested just fine. I hooked the battery up and the light under the hood came on, interior light came on as it should. I turned the key and I heard one click from the starter solenoid I believe and every light was dim after, as if the battery went from a healthy 12 volts to 1 or 2 volts.

 

[michael1989]

I just got my battery back from the charger and it was said to have load tested fine, I hooked the battery back up in my bronco and the lights came on as they should; interior light, under the hood light etc. Then I turned the key and I heard 1 clicking sound, I think it came from the solenoid and the lights went dim like the battery was dead instantly.

 

[Krafty]

bad connection gremlin again

 

[michael1989]

(Sorry about posting the same thing twice I thought it didnt post) Anyways, when your alternator was doing that did your truck even start or did it just click at the solenoid??

 

[Seabronc]

(Sorry about posting the same thing twice I thought it didnt post) Anyways, when your alternator was doing that did your truck even start or did it just click at the solenoid??

The alternator has nothing to do with starting the truck. It can't put out anything unless the engine is turning. It only comes into play after the engine is running. The function of a battery is to start the vehicle, the function of an alternator is to top off the battery and supply the electrical load once the engine is running. The only things in the start circuit are the battery, cables,solenoid, positive connections, ground connections, the things in the bottom left corner of the attached diagram.

If the engine doesn't turn over with a fully charged battery the only possible problems are one or more of the following:

1. Bad cables

2. Bad ground connection at the engine block

3. Bad Connection at the solenoid

4. Bad connection at the starter

5. Bad solenoid

6. Bad starter

You need to check 1 through 5 before option 6, remove the cables at both ends look for corrosion where the lug is attached to the cable, clean all contact surfaces.

That is all there is in the START circuit.

 

[michael1989]

Got it started. The terminals on the battery were dirty and even though I already cleaned them, the cable connections to the battery were corroded. Thanks for the help guys >-

 

[Krafty]

its good to see you got it figured, when my alternators went on my f150, in the spring I had one that was overcharging ( 16 to 19 volts)

then the replacement about 6 months later went out and would sit around 10-11 volts.

put a voltage regulator from a third known good working alternator that would not mate with my brackets, onto the first overcharging alternator and i've been running 13.5 to 14.5 volts ever since, just got me gas money to get the 3 alts in the same place.

here is the link to the thread of my alternator troubles. hope it sheds some light on your stituation.

http://broncozone.com/topic/22354-internal-voltage-regulator/page__p__116628#entry116628

 

[michael1989]

I also took my battery and alternator to pep boys and got them load tested. both passed