Hey guy's out of my depth here with a charging problem. just can't get a charging system problem sorted.new alt. tested and good a couple of known and new volotage regs. tested and good wires tested and good. problem is an overcharge. 13.5 at idle but when revved it goes to 16 almost 17v. revere field wires and it goes back to normal. but wires get really hot. any ideas? car is almost ready for paint and i want this fixed before that . everything on the car works perfect except for the overcharge.

thanks

Sounds like you may need to check the grounds on the regulator and alternator. Make sure the regulator housing is making good, clean contact to the firewall METAL. You may need the scrape the paint off the mounting holes to get this. Star washers help here.

Do you have the firewall to engine ground strap intalled? With the engine running, measure the voltage between the regulator housing and the alternator case. Since both should be grounded, there should be a negligable voltage drop bewteen the two. If there is voltage between the two, I would check re-check grounds!

Hwck if you have the tools, use a 16 ga or lower jumper wire with alligator clips to connect the VR housing to the neg battery terminal. If this helps the problem, grounding is the problem...try the same with the alternator case..

Grounds will get you every time with these cars!

It doesn't matter which field wire goes on which terminal, the field current just goes though the field windings then back to the reg. The reg sends full field current to the alt, through the field windings, then back to the reg. At this point there is no flow of current, so no alt output. The alt output depends on the amount of field current flow. To get flow the current must go to ground. It goes to ground though the reg case. If the reg isn't grounded good the alt won't work. Try pulling one field wire off alt, the alt should not work, if it does one of the brushes is grounded. Try unbolting the reg with all the wires hooked up. The alt should not work, and the reg case should test hot. If the alt does work I would suspect a field wire grounding issue. If everything checks out good, you have a bad reg. The reg is supposed to limit the amount of current it sends to ground to keep the alt output at 14.5 volts. If it is over that, the reg is bad. Hope some of this makes sense.

the first thing i thought was grounds as well so i cleaned the paint off and even made new ground wires for the voltage regulator and the ign. box. the odd thing about the field wires is when they are on one way i get overcharge the otherway it charges right on spec but the wire gets really hot! i don't want to burn it up.

reversing the wires should of not made the difference in a two wire field alt. so now one of the wires gets hot- there is a internal short on the field coil. take both field wires off. now check each terminal to case ground with a ohm meter. and resistance shown is not good.

to me there is a short in the alt.

so if you are grounded well, you should start checking voltages to see if you are getting drops.

the battery voltage, compared to the sensing line on the vr and one of the field lines that doesn't come from the vr.

see how different they are.

so if i am getting this right the feeling is it is a field wire? or the alt ? i have a spare alt and i did a contiuity test on the field wires and they were good but one could be grounding right?

and thanks guy's for the responses keep em coming.

if it's not the alt or vregulator it could be your battery. if there is a bad cell or something it could want more of a charge than needed. i had a similar problem where i tried multiple vregulators and a couple of alternators. the alt could also have a short. i would take both the alt and the bat into a store and have them tested.

the test should be the field prong on the alternator with no wire attached to the case of the alternator.

see if either has continuity. that is the meter goes to 0 instead of showing an open connection.

if you get that, then your alternator has an internal short.

I don't think this is the case, as you would over charge even at idle.

you could check again with the wires attached, and if you see it go to 0 then you might have a short as you thought in the wires to the field.

again, you need to see how close the voltages you are getting are to battery voltage as well.
one field wire carries 12 volts/battery voltage. the other wahtever the vr gives it.

the vr should also should get 12 volts/battery voltage on the sensing line.

losses occur on that due to the bulkhead connector, the ignition switch and just bad connectors in general.
that would cause the sensing voltage to read less than battery voltage and possibly cause over charging.

you can just jump a line from the battery to the balast(far side from the battery, but you will have to check which one has 12 volts key on) and it should up the voltage to the vr and field wire bypassing the bulkhead and igintion and see if you still over charge.

but that doesn't eliminate the possiblity of bad connectors or a shorted field wire.

thanks again guy's the batt. is new and full charge. the field wire is my target i think. one last question am i right in assuming i can put the field wire on either spade terminal on the alt? what possible problems might that cause?

thanks i had the alt tested yesterday but i also have a known good alt i will try tonight.

check that the brush holder is not shorted to the case.

wow this is frustrating! last night after much testing and swapping of parts it was perfect 13.2 or so at idle and 14.5 when revved. start it this morning and I get 16.7 at idle! it is like I have a gremlin in there looking to screw me around! I have tried two different alts. three v regs. a new starter relay new ballast resistor cleaned and added grounds sripped and checked all wires. it seems like we have it sorted then it just starts to over charge again. any fresh Ideas?

i'd take a day or two to be away from it, calm your nerves a bit. if you have a friend have him take a look at it with a fresh perspective. you might go nuts looking at the same thing over and over.

I'd toss in another known good batt for a quick check of a batt internal issue. Reversing the field wiring makes me think something is awry there with the wiring schematics. I'd take off ALL wiring & with jumper wires with alligator clips termporarily rewire EVERYTHING. Batt positive post to reg "top" terminal and to either alt field terminal. other alt field to other reg "side" terminal. reg case and alt case to batt neg post. engine to batt neg. frame to batt neg. Try your larger regular jumper cables between alt case & batt neg post and alt "batt" terminal to battery positive post.

I am going to take a look at it early next week. I think I am going to jump everything to see whats what.

adding my two cents based on an experience I got, since pretty much everything has being talked

ONCE I got between 18 and 24 volts depending RPMs, however NEVER got charge. Made a continuity test and everything was perfect.

make it spin it by hand and quite often could feel somekind of step!!! BARELLY able to feel it

Decided to dissasembly the alt to check what it was happening and FOUND one of the stator leads going to diodes bank somekind worn or with signs of friction.

APPARENTLY some of the fan vanes was slightly touching this stator lead. I pushed out the stator lead, reassembly and everything came out nice.

How this happened suddenly ? dunno... was the rotor able to slide into the rear housing ? is posible the front bearing could move back from front housing... This bearing fits into front housing easy without any kind of real pressure just fit tight but if pulleys have somekind of slight missalignment could happen!

it has happened on two different alternators nacho that is why I have been through all the rest with my buddy who is quite good with this stuff. he is stumped as well! I will try one more alt that I know is good then it is back to the wires.