New alternator, still not enough voltage

[colo525i]

Had charging problems after i put in my new lights. So i put in a new voltage regulator, still no increase. Put in a new alternator, still only 13 volts tops with no load. If you add load, say the blower fan or the lights, the voltage drops and doesn't recover. Soon you are running on nearly nothing. Had the auto parts store test the alt. they managed to get 160amps out of it loaded, but at only 13V. Any ideas? i am stuck until i can get this thing rolling.

[632 Regal]

i would venture to say the new alternator is junk. did you need to swap the pully on yours?

they managed to get 160amps out of it loaded, but at only 13V. Any ideas? i am stuck until i can get this thing rolling.

[colo525i]

Yes had to swap old pulley on there. Here's what i don't get though, i have tried 2 supposedly good v-regulators and this new alternator all with the same results. Voltage just drops when loaded. I did try another battery, i got 14v right after starting, but in a few minutes the voltages tanked. Are there any relays that would isolate the load of accessories from the alternator? I guess i don't see how it could put out all the amperage needed but still have such low voltage.

[Ross]

The voltage regulator is bad, buy a new one

[colo525i]

Ross, i didn't make this clear but i tried that with the original alternator. So i have one voltage regulator that has run all of 20 mins and another that was on the rebuilt alternator. Neither v-reg in either alternator makes any appreciable power nor responds to load. Am i dealing with all bad parts here? Possible, but i find it hard to believe all the new parts i received are bad. Am i looking at a bad ground or something goofy like that?

[Ross]

If it tested only 13 v on the bench I can only conclude a bad regulator.
What happens if you disable the new lights you installed??

[etcetera]

When you are testing this in the car, you are probably seeing the battery voltage drop as loads are added. With a fully charged battery and a working alternator on a running car voltage should be up around 14 volts. I think this goes without saying, but never run an alternator without a good battery. They don't like that.

The new alternator only put out 13v on the test stand? Doesn't sound right at all. Does it put out 14+ volts at any load? Probably be bad. Before digging into the car for the problem I'd return the alternator if possible.

It's also possible there is a wiring problem that is damaging the regulator/alternator.

[colo525i]

the bench test got 14.1 out of the alternator. In car w/ a charged battery it will initially read 14.1, but then will drop as any and all loads are added. This can be the radio, the power windows, the blower fan, anything will do it. When tested in car, it would put out 141amps, but at a max of 13 volts. This is why i don't understand it, it puts out enough amperage in the car, but not enough voltage, and enough voltage out of the car, but an unknown amperage. It does this with 2 voltage regulators that are new. I am leaning to some sort of wiring or relay problem unless an alternator with these symptoms could flat out be bad?

[Blitzkrieg Bob]

and your battery cables, if it's all corroded then it will be producing resistance.

[colo525i]

batt cables are clean, the ground strap is a suspect at this point. I'll check it out.

[colo525i]

.3 ohm resistance between the body and the lift hook on the front of the cylinder head. That is pretty low in my book. I'm charging the batt again, but a charged battery seemed to have no effect.

[etcetera]

.3 ohm resistance between the body and the lift hook on the front of the cylinder head. That is pretty low in my book. I'm charging the batt again, but a charged battery seemed to have no effect.

.3 ohms is high. Should be very close to zero.

Measure from - terminal of battery to alternator housing. Also measure from the + terminal of alternator to + terminal of battery. High resistance between either point won't allow your battery to charge.

E = I x R

E Voltage drop
I current in amps
R resistance in ohms

E=40 amps x .3ohms
E=12 volts drop
With this load there is no charging taking place

E=4amps x .3ohms
E=1.2 volts
assuming 14.4volts output from the alt that leaves 13.2 to charge the battery. Not adequate but at least the car will run.

When I measure mine it's practically zero on an analog meter, unfortunately my digital meter was stolen.

http://epg.modot.org/index.php?title=901.12_Electrical_Components

[colo525i]

I'll test some other wires to make sure it isn't this multimeter as well.. I had no idea that such a small reading of resistance would stop charging...more you know i guess. edit--- looks like the multimeter is to blame for that reading. even touching to 2 ends of a copper wire it still shows .3 ohms...

[Karl]

On my car I added a jumper from the alternator case to the engine block, so the alternator is not grounded through its mounting bracket only, and then another heavy wire from that point on the block to the body connection for the battery grounding strap. That cleared up some charging problems. Cars with their battery under the rear seat have to be even more careful of ground connections, just because of the extra distance and more joints between the alternator and battery.

[etcetera]

I'll test some other wires to make sure it isn't this multimeter as well.. I had no idea that such a small reading of resistance would stop charging...more you know i guess. edit--- looks like the multimeter is to blame for that reading. even touching to 2 ends of a copper wire it still shows .3 ohms...

There might be an adjustment to zero the resistance when touching the leads.

[bill g]

A common fallacy has raised its head here. Resistance readings are often misleading in this type of situation - for example a single strand of wire the thickness of a hair will read zero ohms but will not be thick enough to carry the current. Karls post has given a clue here - you could try installing temporary jumper leads between the components to ensure you have good connections.

Bill G

[colo525i]

Thanks for all the ideas, but nothing has helped as of yet. I have tried jumping the ground from the battery to the lift hook on the engine and to the body. Also have tried jumping the B+ post in the engine bay to the + on the battery. No change from either of those. I am thinking it may be the alternator not grounding to the frame somehow. Are there any relays/diodes etc that could not close properly and cause a bad ground as well?

[bsell]

Thanks for all the ideas, but nothing has helped as of yet. I have tried jumping the ground from the battery to the lift hook on the engine and to the body. Also have tried jumping the B+ post in the engine bay to the + on the battery. No change from either of those. I am thinking it may be the alternator not grounding to the frame somehow. Are there any relays/diodes etc that could not close properly and cause a bad ground as well?

So you did not touch the jumper to the case of the alternator itself during the negative circuit check? That would remove the bracket as a suspect. You might have to break the bracket bolts loose and retighten to get clean electrical contact.

The last jumper check I can suggest is to bypass the car's wiring and frame by using two jumpers, one from the case to neg bat post and the other from the B+ on the alternator to the pos bat post. Of course good quality jumper cables (meaning fat boys!) are in order for this test. If the reading is still low at the battery with above idle engine speed, you have a ghost in the machine!;) or bad jumpers too. :(

You already cleaned the connections at the battery to remove any old skin effect problems, right? Cleaning all of the ground connections between the block and the car and the battery to car may be the only other recourse. I have found the source of similarly frustrating situations after checking every wire/connection in the circuit. Tedious but necessary.

I take it you got your 141 amps output with the engine revved above idle...

Brian

[colo525i]

I'll give the alt shell to negative battery route a try. When they did the load test on the alternator it managed to put out 141 amps at 2000 rpm but 13 v. It was hooked up to the B+ post and the lift hook. So it would seem the resistance/bad connection is between the B+ and alternator or the bracket and the engine itself. Does that seem correct?

[632 Regal]

after all this anything seems correct, I have thrown cars away with similar electrical nonsence.


I'll give the alt shell to negative battery route a try. When they did the load test on the alternator it managed to put out 141 amps at 2000 rpm but 13 v. It was hooked up to the B+ post and the lift hook. So it would seem the resistance/bad connection is between the B+ and alternator or the bracket and the engine itself. Does that seem correct?

[colo525i]

Hah, I'm about at that point myself!

[colo525i]

Well after all this it is fixed. a $4 4gauge battery cable that has the same size post openings as the ground strap fixed it. I checked the resistance and connections on the ground, without taking it out and flexing it. When i did that it made a sickening crunching noise, not enough wire to move the current needed. Takes a while for the OBC to show 14.1 after you go from a stop, but driving down the road it never dips below 13.7. Problem solved.. finally! :D Thanks to Bill G for reminding me about the "just because there is no resistance doesn't man the cable is good" principle.

[bsell]

Well after all this it is fixed. a $4 4gauge battery cable that has the same size post openings as the ground strap fixed it. I checked the resistance and connections on the ground, without taking it out and flexing it. When i did that it made a sickening crunching noise, not enough wire to move the current needed. Takes a while for the OBC to show 14.1 after you go from a stop, but driving down the road it never dips below 13.7. Problem solved.. finally! :D Thanks to Bill G for reminding me about the "just because there is no resistance doesn't man the cable is good" principle.

Glad you found the nasty bugger!

Did you think about redoing the voltage drop test to see if that got all of your problem? The reason I ask is the positive cable is just as old (but doesn't see the same flex) as the ground cable and could be corroded internally causing high resistance to massive current flow...

Brian

[colo525i]

Well i spoke too soon. While the car will run the first time you go with 14.1 volts with full load, (headlights/ac/radio) As soon as you slow down into city traffic with that amount of load, the voltage dips and never recovers. If i charge the battery externally it will run up to 14.1 again, but will fall as soon as you get off the highway. Could there be something wrong with the battery as well?

[bsell]

Well i spoke too soon. While the car will run the first time you go with 14.1 volts with full load, (headlights/ac/radio) As soon as you slow down into city traffic with that amount of load, the voltage dips and never recovers. If i charge the battery externally it will run up to 14.1 again, but will fall as soon as you get off the highway. Could there be something wrong with the battery as well?

Sounds heat related...did you check all of the other connections/wires back to the battery to include cleaning all of the grounding points?

I wonder if you have a rotten cable running along the floorboard from the engine to the battery that gets hot and resistive over time. I swear I've seen this kind of mess before and finally found it by flexing a positive cable and hearing the crunching noise from the corrosion under the insulation. To look at the wire, you wouldn't have suspected it was garbage but once I cut the insulation off of it, what a mess!

You can find the culprit, you just have to hang in there and be thorough in your search.

[colo525i]

Ok figured out the common thread to all my "low voltage times" It had either rained earlier or was raining meaning high humidity. I am thinking something in the engine bay as it would be most affected by outside humidity changes. I am going to try to patch between the b+ post and the alternator output to see if that helps.

[bsell]

Ok figured out the common thread to all my "low voltage times" It had either rained earlier or was raining meaning high humidity. I am thinking something in the engine bay as it would be most affected by outside humidity changes. I am going to try to patch between the b+ post and the alternator output to see if that helps.

High humidity created electrical problems makes me think crusty grounds are at fault, as in a connection or wire somewhere (outside more than likely) has an air gap (due to corrosion) that gets more resistive with increased humidity.

I had an older Skyline that stumbled coming off-idle when it was hot out. Chased it for a year before finding it.:( The internal connection from the circuit board in the MAF to the external connector had broken the solder on all six-eight pins. When it got hot or humid out, the resistance would pop up due to engine movement and cause the stumble. A quick re-solder and away she went for the next four years (sold the car).

Seek and ye' shall find...

Brian

[colo525i]

Had the same problems this morning with low voltage. Decided to pull the grounds near the front turn signals. Sanded down all the connectors even though they were fairly clean. Voltages came up and have stayed up since. It shows 14.17 while running on the OBC where it only would peak at 14.10. Fingers crossed they were just resisting a bit..

[colo525i]

Hate to revive an old thread but my problems have not gone away. I have bypassed every bit of wire from the alternator to the battery to see if i could find a bad piece of cable, but to no avail. I am on my second replacement alternator with the same results, low voltage when loaded. Here's my list of replaced stuff. Alternator x2, ground strap, battery (new duralast). I have even tried to bypass the front cable from the alternator to the B+ post but with no change. Is there any other part of the charge system at all? 2 shops have been unable to figure out what is going on, the bmw dealer charges $100/hour labor, at which point i'd be better off scrapping the car.

[colo525i]

Well after all this, it turns out i am a moron. The belt was on wrong, going over the idler pulley next to the alternator instead of under it. The belt was loose, but not squealing. It is also much easier to get the belt on this way :p If anyone has a random problem like this, make sure to check the belt routing, it is far too easy to overlook!

[Ferret]

Sounds heat related...did you check all of the other connections/wires back to the battery to include cleaning all of the grounding points?

I wonder if you have a rotten cable running along the floorboard from the engine to the battery that gets hot and resistive over time. I swear I've seen this kind of mess before and finally found it by flexing a positive cable and hearing the crunching noise from the corrosion under the insulation. To look at the wire, you wouldn't have suspected it was garbage but once I cut the insulation off of it, what a mess!

You can find the culprit, you just have to hang in there and be thorough in your search.

If you're checking your voltage while running through the OBC are you sure your fusibile link is in good shape?

Heat would cause this to go funny...

[bones]

electrical issues can be really frustrating,keep it simple,if the alternator put out 14.1 volts on the car initially and then degrades with a load i would suspect the battery .possibly a bad cell.the alternator is telling you that you have got enormous current draw going on.when you start turning on accessories does it affect idle speed?does the engine pull down slightly? this is also an indicator of current draw.swap the battery if there is no change,pull the headlight connectors and remove them from the circuit.still no change,pull the 80 amp fuseable link and test again,if there was no charging issues prior to the headlight task i would really check that area well.was it a simple plug and play swap or did you have to modify or repair the wiring? bones

[bones]

one last thing,a bad starter motor that is shorting internally would produce symptoms identical to what you have. bones

[Ferret]

The Conversation splits in this thread are hurting my head :s

Totally missed that you'd said it was fixxored because of the belt - the thread itself was hiding the responses.

[Tiger]

Damn! You definitely are! ;) Geez! I am wondering if your old alternator is good too... Don't touch it!

[bsell]

Well after all this, it turns out i am a moron. The belt was on wrong, going over the idler pulley next to the alternator instead of under it. The belt was loose, but not squealing. It is also much easier to get the belt on this way :p If anyone has a random problem like this, make sure to check the belt routing, it is far too easy to overlook!

I figure this belt thing happened for a reason. You did find a buggered ground wire and a cruddy ground point so all that effort was not lost. I figure your alternator was working harder than it needed to overcome the resistance problems you fixed. So hopefully your new one will last on the cleaner electrical system you now have.

Brian