I wonder if some how its adding the pos and neg voltage of the AC voltage sign wave? Because half of 28 would be 14, but still it doesn't make sense.

 

Before being "rectified" (that sounds ominous) into DC, how many AC volts is a normal alternator producing ??


Thanks.

 

BearKiller your persistent. I'd throw away the whole mess and hooked up a Delco Remy 1 wire alt. by now. But i've had stuff that just chapped my chops and wouldn't quit till I had an answer. I was talking to an old guy that used to rebuild alternators, starters, generators, ect. and he quit due to lack of quality parts and the cheap china junk rebuilds finally he just quit. Keep posting your results so we can learn something here. Good luck with it.

 

Yeah, I can worry a light-pole out of the ground; it comes from a lifetime of poverty and need.

 

Ok,i went trough all that,could not get it to charge prop. cut the wire that went to reg 12v switched and ran it to batt,had 14.5 ,i ran 12v pos with a relay,worked fine for may a mlies.Also sometimes the grid heater sol. stick intermitinly causeing headaches,if they are stuck the reading when charging is less than 12v as alt will not keep up to heater,even one grid.

 

Please go into a little more detail on that.

Did you splice a relay circuit into the BLUE(ign.) wire, sending it direct to the battery and let the KEY-HOT end of the BLUE wire be the trigger-wire for the relay ??


Was your's killing/eating regulators ??

Thanks.




The big fat grid-heater feed-wires have been dis-connected and laying loose behind the battery since the first day we got the truck, so no amp draw there.


Thanks.

 

Just for comparison's sake, could some of you check the AC-voltage at the battery, both with engine running and engine OFF, maybe on other vehicles as well, and post your findings ??


I also intend to find someone with a really-accurate meter and see if they will check it against the AC readings I have gotten with my two old poor-man's meters.(trouble is everyone in my area is either too poor or too miserly to invest in better equipment.

 

This wasn't on a Dodge but about 15 years ago when I was a part time local rebuilder I did a rebuild for a fellow with a Chevy S10. He Just installed a new Sears Die Hard battery along with the alternator that I had rebuilt for him. The alternator heated up and the voltage rectifier had failed. Under warranty I replaced the regulator with another new one. In both cases I bench load tested it using a carbon pile load tester until I knocked the voltage down to around 8 volts DC for around 20 - 30 seconds. There was no excessive out of the normal temperature rise noticeable. Installed it on the truck with a nearly full charged battery and within a matter of a few minutes you could not keep your hand on it. Pulled out his new battery and put a temporary used one in and it ran just as it should without heating up. He took the Die Hard back to Sears and bought and installed a new Motorcraft battery. The truck continued to run that way for the next few years that he owned it without any alternator problems. So, yes, in this particular case the battery had some type of a problem that was causing the alternator to run at full output (as tested at 14.7 VDC).

 

Around 90 volts when full fielded.

 

I cut the wire to test it,tryed everyhing else so what could lose,ign swich is prob the falt,when i ran power from batt aways had 14.5 tied wires back together not using batt. sourse charging whent crazy so a ran a relay useing keyed wire to acavate relay.3 years and no trouble,used to have spare reg.mounted,

 

I did some research on the weird AC-voltage readings that I was getting.

It seems that if one's multi-meter is not automotive-specific (there is some kind of RJM-rating or somesuch that will be labeled on the automotive ones), then the meter's battery can somehow distort the readings when checking for ACV on a DC system.

If one reverses the leads, putting the Red lead on Negative, Black lead on Positive, it will yield a more accurate ACV reading. (I wish I had of known this at the beginning of this episode.)

I have no idea what the true ACV reading was on the original alternator, the one that killed two regulators in the same day, as it is not on an engine at the moment.


I have also been advised that when a rectifier fails, the alternator will remain active after the engine is OFF, getting hotter and hotter, until either the battery is dead, or something is on fire; I can't verify this information but I did once have a farm tractor to start smoking at the alternator, sitting parked half-an-hour after I shut it off, and it melted every last bit of insulation from every single wire on that tractor, EVERYTHING, before I could get at the battery to get a cable off; had I not been there, the entire tire-shop would have burned for weeks.

That could also explain many of the mysterious vehicle burnings that happen hours after they have been parked for the night.


I was also informed that a sure regulator killer is a short in the "field".

I don't know if such a short is findable/fixable by someone such as I, or even if that is the problem, but I intend to find out.



The current status of the truck :


Extra spare alternator got a tachometer pig-tail installed, all points of electrical contact wire-wheel brushed good and shiny, all bolts anti-siezed, and mounted on the engine.

I piggy-backed a second 8AWG charge-wire and routed it direct to the HOT post at the battery; I left the existing O.E.M. charge-wire intact; it looks to be about 6AWG.

A new el-cheapo voltage-regulator is mounted and well-grounded.

I even spliced the regulator ground onto the entire ground system for all the auxilliary lights and accessories; in other words, I always run a dedicated ground-wire plus any chassis-ground that the mounting-screws obtain, such that besides being grounded at the wire, all ground circuits share all the grounded attachment points.


After sitting all night and most of the day, Group-31s battery shows 12.7 DC-volts.

Engine ON, brights ON, DC-voltage at the battery = 14.9 (cheap chinese regulator), AC-voltage at the battery = -0- (with leads reversed)


She has been on a few little test-runs and so far all is well.

I am gonna give it a couple weeks, and if all is still okay, then I will mount another good MOPAR regulator; if something does go haywire, it don't hurt hardly so bad to lose a $17 regulator.








NOW, where can I get such things as new brushes, bearings, and other necessities for rebuilding these particular alternators ??



Also, is there a TECH article hidden anywhere on this task ??

Thanks.

 

I did not know that about the AC readings, mine have always been low to non-existent on my meters.

A short in the field would be most likely caused by melted insulation in the windings on the rotor. The rotor would need to be rewound, not really a DIY project unless you have a good supply of magnet wire and a lot of spare time.

If the diodes in the rectifier fail in such a way that they pass current in both directions (rather than just blowing and causing an open circuit), then the alternator will drain the battery and even start a fire as you described.

Brushes, at least.
http://www.fostertruck.com/alternators.htm

 

I got my letters wrong in the previous post; apparently, to get accurate AC readings on a DC system, the meter needs to be an RMS.Can I determine this with the alternator on the bench ??


Can I determine whether or not the diodes/rectifier are good/bad on the bench ??


Thank you.

 

You can check for a shorted field using an ohmmeter.

Jim Lane probably knows how to check a rectifier.

 

Do I check for a short from the windings to the alternator-case or a short between two seperate windings ?? or both ??


Thanks.