Hi, well when the gauge in my truck lowers, so does my headlights, A/C blower speed, and dash dims. I'm going to pick up a voltmeter tomarrow. WHat should I test. I really need to fix this problem. Does anyone think it could be a battery? I really appreciate all the GREAT help!!!

 

Exactly, that's the problem. The G2 alternator can't keep all the electricals supplied with 12.8 volts. So it relies on the battery and this draws down the battery eventually. Maybe when it was new and all the connections were spanky clean it was just border lind. It also ruins the electricals components that should be getting 12.8 volts overtime. Of course the 2G alternator is working at max capacity during this whole time. So it dies an early death anyway. Do the conversion or power down some of you electrical demands. The 3G is really pretty easy to do. I bought a new one from pep boys and built the harness myself, so I was out only $200 for the whole deal. Now only time will tell if a pep boys alternator is going to last. But it seems no one does a decent rebuild on alternators anymore. I had a NAPA gold supreme or whatever only last 90 miles before it fell apart, .....another story.

 

if your new alt is really putting out 75 amps that should be enough to run all accessories and not drain the battery. maybe your new alt is not able to put out the 75 amps. do you have the correct battery in the vehicle? when the engineers design the system some battery drain is figured into the equation so they require you to put in a certain amperage battery so you are not left stuck. many moonbs ago a big problem with charge systems and plow trucks with electric pumps was that the batteries woulld drain and the stop and go of plowing the alt could not keep up with the drain.if more than one battery was listed for the bronco i hope you bought the best,most cca and amp rating.i feel a 75 amp alt is really very borderline but should do the job if you arent plowing. most newer vehicles have 100 to 120 amp alt and a big capacity baterry to make sure there isnt battery drain while running with all accessories on.a fluke meter is the top dog but a 60.00$ meter will do the trick. you can series the meter in tothe chargeing circut to check chargeing amperage if the meter is rated to say 100 amps @12vdc. if not dont blow a 60.00$ meter

 

At the risk of being lambasted again for my opinions on electrical theory, the neg. cable disconnect is ONLY harmful if you RECONNECT it with the key on.... Hello, turning the keyswitch to the "off" position disconnects the POSITIVE side. The concern over damaging the components that are sensitive to voltage spikes is an issue for voltage INRUSH not disconnect. So, shutting the system down, whether its by turning the key or pulling the battery cable, has the same effect.....the problem is in the reconnect. Reconnecting with the key ON leaves the possibility for current spike. Turning the key off before reconnecting is critical. Thats when the possibility for a spike occurs. So, I still hold to my idea that using the time honored practice of pulling the neg. battery cable to test for a dead alternator can still be done on newer vehicles BUT the key MUST be turned OFF prior to reconnecting to eliminate the possibility for component damaging spikes.

And again, I will say this. Anyone capable of giving me a sound reason based in electrical theory as to why this is still a bad idea, I welcome the criticsm.

 

I agree with your synopsis..I'm not real sure it would even "spike". It may shock the system, but without capacitors it would only have the inrush of what charge was in the battery. My .02

Wayne

 

well here is my 2 cents.when you pull the battery cable either one,it puts the alt. into full load no battery,so anything on or operating is sent the full load of amps,put 75 amps to a computer controled item and it is toast. some items are fused some are not.so that is why you should not pull the cables.the voltage gage reads same at the battery and alt. volts.if you check the battery volts and alt. they should read the same.the voltage regulator does exactly that it regulates voltage so it doesn't over load any items. is your ac is killing the gage or the blower motor it could be dragging because of age.

 

me again a rebuilt alt. is rebuilt with ONLY WHAT IT NEEDS. not everthing is replaced(rebuilt).if they put everthing new it would be a new alt.they clean inspect replace what is needed and sold to us.

 

"the voltage regulator does exactly that it regulates voltage so it doesn't over load any items"

including the EEC!

 

I have had pretty good luck with using a screw driver, and touching the diode(s) on the back of the alternator. If the screwdriver magnetizes, the chances are the alternator is working...unless it's the built-in voltage regulator causing the problem. A lot is dependent on the application and alternator. Bodyman is correct...you get what you pay for!

Wayne

 

your baterry is in the circut also to filter the voltage . a diode pack converts the ac current to dc but the dc is not that clean. diodes of this quality are expesive when they need to handle the current an alt can put out. i agree that the chance of spike is more likely to happen on the reconnect but is it worthe chance.now for the voltage regulator, it has nothing to do with protecting electronic items from overload. it senses baterry voltage and lets just the amount of chargeing current that the battery needs to stay fully charged. all vehicle power is taken from the battery because it is filtered voltage coming from there. say you are draining 40 amps to run all of the accessories the regulator should be letting 40 amps get back to the battery. if it let the full 75 amps the battery would overcharge and would last for diddle. greystreak i didnt mean to upset you but we all have are beliefs. i just feel it is not worth the chance of frying electronics and they are expensive.

im not saying i know it all but i have been an alarm tech with 20 years of low voltage dc expierience and just have seen this frying of electronic parts happen all to many times,
. again didnt mean to start a disagrement.

 

body man chuck it is true that you would hit the whole electrical system with the 75 amps but the devices will only use what they need but now we have to get rid of the extra current and it does this thru heat and we all know heat kills electronics.

 

well that's why we are all here talking.we all can learn something from one another.BOJOFASO your alt. detail was right on the money.

 

BOJOFASO, not upset at all, just been down this road before and been stomped on by the site admin. for my understanding of electrical theory. The short answer here is simply that electricity WILL NOT FLOW without BOTH sides of the circuit in place. Left "ON" a CAPACITOR will continue to charge until it is triggered or reaches its discharge capacity. Otherwise, electricity with nowhere to go, will sit and wait for eternity.

If the either the pos. OR neg. cable is disconnected, the flow of eletricity STOPS. It doesn't back up in the sink like water. The only way it can do that is with an eletricity sink (capacitor). Amperage is the measure of how much is going through the system. And, as it has been stated, will only be used if it is needed. Amperage is measured by how much electricity is being "pulled through" any given system by the components in the system not by what is sitting there waiting. A 75 amp alternator is capable of handling a maximum amperage draw of 75 amps. If your vehicle only draws 60 amps when everything electrical is running, then the alternator will provide 60 amps and 60 amps ONLY. If the vehicle draws 85 amps under the same conditions, the alternator will provide ONLY 75 amps (and die trying to compensate for the additional draw).

If you remove the neg. from a light bulb, it goes out just like if you remove the pos.. Electricity needs a two way street to function and if you break that two way flow, it just doesn't go anywhere. Even if you pull the positive cable, the result will be the same. If you remove the positive battery cable, and the alternator is actually putting out....the system will see no change anyway. If you pull the pos. cable and and the engine dies, you simply turned it off. You merely turned off the engine circuits AND all the other circuits in the vehicle as well. The problem with reconnecting after the engine has stopped spinning is that the ignition circuits are still "on". However, if you think about it, the same thing happens if you flood the engine going through a puddle or it gets starved for air or fuel. Engine stops spinning...ignition circuits are live. Seabisquit had an even better point in that the maximum inrush current on the reconnect would be the maximum charge in the battery. 12-14 VDC...Gee, isn't that what those circuits are designed to run on anyway?

If the voltage regulator fails on the "over volt" side, it is entirely possible to send too much electricity through the system because the alternator is capable of much higher voltage output than the regulator allows through. However, even if the alternator is churning out 24-30 volts, if you pull the neg. cable the flow of electrons still stops. In the case of a failed regulator on the overvolt side though, pulling the positive cable will do nothing as the alternator is still tied directly to the onboard circuitry via the pos. cable back to the battery. And with the neg cable still in place the electricity still has its two way street.

As I already posted, the practice of turning the key off PRIOR to reconnecting is a good precaution just because it leaves a zero load on the battery at the time of reconnection save for a few minor circuits like computer and radio memory and anything else one may have tied directly to the battery and not the "acc" side of the ignition switch.

 

Amperage is the actual flow rate of electrons. Voltage is like pressure ("umph").

 

A internal regulator senses the alternator terminal voltage, varies the power fed to the field of the alternator to keep the terminal voltage constant irrespective of load conditions. This is achieved by thyristor controlled rectifiers where the triggering phase angle of the thyristor is varied by fast acting highly sensitive solid state control circuit.