my 48 olds is finally roadworthy and during this initial shakedown period. things are wound to .. well.. come up. currently I am having a charging? issue.. car starts great, runs great.. will sit and idle all day without heating.. so far its voyages around the neighborhood have proven no ill handling.. but.. I am noticing that when the car is running i am only getting about 12.4 volts at the batt (checked with digital vom hooked directly to the battery..) and if I pull the lights, the car wants to die i've checked and double checked grounds, batt to frame, frame to block, etc.. 99% of the electrical issues I've run into have been grounding issues.. but I am stumped for what its worth.. non trad 350 with a dumb old 3 wire chrome alternator.. the alternator and the batt have been checked by my local parts house.. (off the car) and both check out ok.. any ideas?
old 3 wire alternator...what does it look like, where the two wires plug in? are they parallel or in line? One style needs an external regulator, the other does not
inline.. manyolcars? crossgrounded? ok.. well after I check the headlights, I think I'll toss this chrome alternator once and for all and install the rusty old alternator just to make sure..
If its a internal regulated gm alternator the wiring is very simple, the main stud on the back is 12 volt +, so it can be hooked to the battery or to the battery cable on the starter, it should be 10 gauge or so. The plug should have a red and white wire, i put an eyelet on the red wire and hook it up to the post on the back of the alternator where the power wire is, so thats basically 12 volt + also. The white wire would be the energizer wire, that would hook up to the accesory side of the ingnition switch. And it your batt voltage is reading 12.4 its not charging, a battery sitting in a car with nothing going on thats basically fullly charged should read about 12.6 or a little under volts, so yours reading 12.4 means the ignition is pulling some power and the alt is not charging. and .1 is a big difference in volts, a battery that reads 12.0 or 12.1 is a very dead battery. each cell puts out 2.1 volts so 2.1 x 6 for a total of 12.6 volts charged. Now Gms are wired a little differently from the factory, they have the other power wire hooked up in a different spot, not sure why, because the power is still the power weather you get it from the battery or the starter cable etc etc. Another quick way to tell if the alternator is charging correctly is to hold a scew driver or wrench to the back bearing on the alternator, if its magnatized its charge, no magniatism no chargy And the pics below are of the internal regulated alternator and plug, they are pretty fool proof, if they tested good they are prabably good.
with the 10si shown above you need either a warning light or a wire from the ignition switch with a diode in line to start the charging process. on back of alt: large post goes to battery 10g wire min 1 goes to warning light or ignition switch with a diode 2 goes to a 12v (the large pos post on the back) also the plugs for the alt are either a square (external regulator needed, shown below) or a rectangle (shown above) is the internal regulated version. for the diode Radio Shack # 276-1661 (per rebel wire)
Ive only had a few that needed a diode, i think it realy depends on the type of igntion switch. Basically the diode keeps the alternator from backfeeding power to the igntion and keeping the car from shutting off when you turn the key off so basically i always wired them up like the way above i posted and if the car wouldnt shut off when the key was shut off then i added a diode. its usually an ignition switch that doesnt have a seperate circuit for the ignition power
If its an internally regulated alternator, the white wire is the load sensing input wire. I always have wired this wire to the acc side of the ign switch, when the key is turned on, power flows to the alternator, telling it to charge, which it does, feeding power backward through this same wire to the ign switch. You need to hook up to the acc side of the switch cause its dead when shut off, thus killing the engine, hook it anywhere else and it'll backfeed and not allow you to kill the engine. I have never used a diode, although you can, the above method is foolproof and easy, try it. Hook the red wire to the bat post on the alternator and shazzam, you'll have power.
sounds like a good plan, except for the pesky fact that my old Chevys don't have an ACC position on the ignition switch.
Just humour me here, put the chrome alternator, the one that tested good at the parts store back on, and tighten the belt up tighter than you normally would. I have had this exact problem a few times and that's what it came down to. I had an oldsmobile and I would not have believed the belt was slipping, but it was.
jeff (titus.. ) first thing I did (after the parts store verified that the alt was good) was reinstall and test the alternator on the car with the old "screwdriver to the back" trick.. and alas it checked good (ie shows that its magnatized!) I've had a number of cars with an identical setup and never had to use the diode.. but.. will keep that in mind.. I have this bad feeling that stllrng is going to have the correct answer.. unfortunately it'll be a few days till I have time to check it out. the other thing that just occured to me is perhaps I should try a seperate ground wire from the body of the chrome alternator to the block? just to ensure that I have a good ground from the alt?
Weird, if its magnatized that should mean its charging. have you checked the volts again? also if the belt is slipping a quick look at the alternator pully will tell you cause there will be black belt dust everyhwere. The diode thing would only be a problem if the car doesnt shut of when you turn the key off. JEFF
OK, you may not have thought of this one, but it happened to me, and it took MONTHS to finally figure it out. If you've got a chrome alt., and pulley, the belt may be slipping enough to put out a little charge, but not enough to get to 14.3 volts. Mine would even get to 14 or so at idle, but when under higher load...faster speed, it would slip enough to not charge the battery. Alt always tested out fine at the shop, and checking it at idle, but my battery was always on the verge of dying, I'd only have one chance to get'er started. If it didint' fire, the starter would just click. Take the pulley off and sandblast the belt portion with coarse sand.
The belt thing is a good idea.... I have a belt tension gage and I use it whenever I tighten a belt, so I forgot all about how this can screw things up. Chrome pulley plus loose belt equals low voltage.
You know what a voltmeter tells you. What does an ammeter tell you? (If the screwdriver to the back to the alternator trick means dead shorting the output you could have fried the (internal ?) regulator.
12.4 v is a no charge condition. It also indicates a partially discharged battery, which is confirmed by the headlamp load killing the engine. Put the battery on the charger overnight. You need to see a resting voltage above 12.7 Alternators are not "magnetized" like a generator. The "screwdriver in the back" trick only works on some models of Delco internally regulated alternators. There is one place to short a tab on the regulator to case ground with a small screwdriver. What this does is apply full field power for output testing. You should monitor output voltage when performing this test, because it can cause very high charging voltages. You can't just poke a screwdriver through any opening on the back of an alternator - unless you like spending money. GM & Ford alternators need a resistor on the run circuit. The warning lamp provides this function. If you are not using a warning lamp, you need a 470 ohm, 1/2 watt resistor in that circuit. B.
My statement about the scewdriver is just seeing if the alternator is magnatized, not touching any power source with it, the back center bearing is magnatized when the alt is charging, its technically like holding a plug wire to see if the ign is making spark. JEFF
Are you running a powerful electric fan?Maybe pulling a good bit of amps on its own,then with the headlamps might be asking to much from your alternator if its a 60 amp model.Just thinking.Good luck.
mines wired with a rebel kit, and home brewed 1 wire conversion. I have no diode or light in the circuit and it works perfectly. It does however require me to blip the throttle to "wakeup" the alternator on startup.
I have seen many belts slipping with no signs of black dust anywhere. Believe me, the belt can be driving the alternator just fine at low idle and begin to slip as the speed is increased, and there often is no noise either.
Stllrng makes an excellent point. Pulleys wear and it is hard to tell. Also, the belt may be the wrong angle for your setup. To check for worn pulleys or incompatible belts, do the following. Remove the suspect belt. Coat the entire working surface of the pulleys-insides and bottom of both the crank and generator with a magic marker or layout dye. Replace the belt, tighten and run the car for a short time. The belt is supposed to ride on the sides of the pulleys on the "V".The dye should be worn off the sides of both pulleys corresponding to the sides of the "V" on the belt. If the dye is worn off the bottom, the belt is wrong or the pulley is worn out, causing slippage and lack of charging. Either pulley, or the belt may be the problem. Good luck
Trust me i know, all i was saying was to look for a quick tell tale sign first. I worked in the auto parts business for 12 years, ive had to work with customers to solve many problems with alternators that they thought were defective etc etc, lots of belts belt tensionors and electrical problems were found.
The diode is if the car won't shut off with the key as mentioned. If the alt works at the store, check for belt slippage, add a quick ground wire (set of jumper cables to the battery) and make sure your getting 12v to the back of the alt.
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