Electrical charging system question, Alternator? Options

[rjames]

I installed a brand new battery and a new voltage regulater last week in the car. My volt meter is showing 12.5 volts at the terminals. With the car running and the lights and fan on my volt meter fluctuates between 12.7 and 12.9, then slowly starts to dip, getting as low as 12.5 before I decided to shut the engine off because I could see that the battery was slowly draining.

Would it be logical that the alternator might need replacing? The alt. belt also seemed tight (not sure exactly how tight it should feel though.) I can check the electrical connections (have to find them first though.) The connections at the battery all look good though.

It doesn't look like a fun job to replace the alternator, but I'm up for the challenge. Anything else I should look for before I go this route??

Thanks!

PS: Forgot to add that the alternator light on the dash comes on when starting the car, but goes off right away once it's started and doesn't come back on at all when driving.

[davep]

Check the ground circuit: measure the voltage difference between the negative post on the battery and the fan shroud. The alternator grounds through its case to the fan shroud, then the engine, transmission, up the ground strap and through the body to the battery strap and then the post. That is a long path with lots of connections. If you get much of a voltage difference, then start checking the ground straps. If you are relying on the console voltmeter, then forget it, since it never reads correctly. A DVM is the only tool to do this sort of a test.

[nycchef]

had a similar problem. are you sure the regulater is good?. if there is any doubt check my post "atlernator problems is anything simple?" on page 6 of the garage forum. there is a test you can do to test the regulator. good luck

[rjames]

are you sure the regulater is good?.

The voltage regulator is brand new.

Check the ground circuit: measure the voltage difference between the negative post on the battery and the fan shroud. The alternator grounds through its case to the fan shroud, then the engine, transmission, up the ground strap and through the body to the battery strap and then the post. That is a long path with lots of connections. If you get much of a voltage difference, then start checking the ground straps. If you are relying on the console voltmeter, then forget it, since it never reads correctly. A DVM is the only tool to do this sort of a test.

I'll try this, thanks!
And I'm using a digital volt meter to get my readings (not relying on the POS one in the car)

[rjames]

I also noticed that the idle speed drops when I turn the lights on. Not sure if that is telling of anything...

[bd1308]

I know the regulator is brand new, but I have personally bought "bad" new regulators. The light will go out on the dash and everything too, when the regulator is out. Trade it in and see what happens.

There's something about today and Quality Control which I don't understand.

b

[rjames]

had a similar problem. are you sure the regulater is good?. if there is any doubt check my post "atlernator problems is anything simple?" on page 6 of the garage forum. there is a test you can do to test the regulator. good luck

nycchef: I read your thread, and will try the method described therin. The one question I do have concerning shorting the regulator connection to see if the alternator kicks in is this: Is it possible for my alternator to be working -a little-? Maybe charging the battery enough so it just runs down very slowly? I ask this because if I hear the alternator kick in, does that necessarily mean it's charging the battery as much as it should be?

[davep]

Don't try removing the battery from the circuit like nycchef, that is bound to cause damage. You should be able to to use your DVM to do all the necessary testing. With the engine at idle the DVM should show higher volts than when the engine is off. Bring the engine up to 2000 RPM and the DVM should show higher volts again. Engine off volts on a good battery are about 12.8, at idle should be over 13 and peak volts should be close to 14.

Even at 3000 RPM cruising it will take several hours to recharge the battery.

[nycchef]

i should have pointed out in my thread listen to the other guys not me. i'm learning as i go

[rjames]

All good info, will be testing tonight. The thing that got me checking on things in the first place is that I just bought a new battery, put it in and was amazed at how bright the turn signals were. I could actually seem them from inside the car. Measured the voltage which was close to 13 with the engine off. Drove around for a day or two, then the turn signal indicator inside stopped working after a couple of blinks, and the turn signals weren't as bright, and with the headlights on the RPMs dropped by 200. Seems like classic alternator problem, but then again with these cars very little is often obvious to me.

[rjames]

I just got done reading the Pelican article regarding troubleshooting the charging system:

http://www.pelicanparts.com/techarticles/9...roubleshoot.htm


After reading this it would seem that as long as the right bulb is installed for the alternator light then any charging problems should light the bulb. My charging light goes on when turning the key to the on position, but after the car starts it goes off right away, and does not come on at all when driving. I suppose this doesn't really change how I should test things, but wonder if it points to something specific (other then, hey- there's something wrong with my charging system!)

In looking at the article, there are 2 tests I should peform and of course I have questions about both as I have limited experience with electrical issues and don't want to die or get shocked, or ruin my car while testing.

TEST 1)Connect +12 volts from the battery to the DF terminal on the relay board.

So with car running I connect run a wire from the positive post on the battery to the DF terminal on the relay board. Is the voltage regulator still plugged in for this test? Is there specific cable guage I should use for this test?

TEST 2) To check the D+ portion of the system, it is necessary to find out if the D+ output can produce enough current to drive the alternator to full output. To do this, short the D+ and DF terminals on the relay board. This will provide the maximum field current to the alternator that the alternator ITSELF can supply (not the battery, as in the earlier check) and so checks the remainder of the circuitry. If this test puts the light out, then the alternator is good, and the trouble is elsewhere.

Should this test be done with or without the VR installed?


Again, be patient w/me as I haven't worked much with electricity in this capacity. I learned how to weld and fixed the longs on the car this year just from reading posts on this board so I'm sure I can learn to troubleshoot this stuff as well. I just needs some guidance.



One more idea, could my charging woes be from a slipping belt? I don't hear any noise that would indicate it. Is there a way to test if the belt is slipping? (Other then sticking my fingers back there...)

As always, thanks everyone for the help- if nothing else it will enable me to help someone else out at some point in time.

[rjames]

Still hoping for some more feedback on the previous posting, although everyone is probably board of this thread.

I tried another voltage regulator with the same results. I got excited when I first put it on, the car read 14+ at idle, and then steadily went down right away and hovered around 12.2- 12.5 at idle. (IMG:style_emoticons/default/dry.gif)

[Dr. Roger]

(IMG:http://www.toolweb.com/pics/LIS11120.jpg)

lead is shiny when clean, dull grey when oxidized and resisting conductivity.
first things first. clean the battery cables with this handy little wire brush cleaner.
then ensure you've good good ground from the batt to the body. Zero ohms resistance.

charging systems sense low voltage. below a certain point the voltage regulator clicks "on" and charges until a max voltage is reached. usually 13.6 to 14.2V.

the way i check a charging system is to load the battery on purpose by grounding the coil and turning over the engine for 5-7 seconds.
this will ensure that the charging system will be "triggered" on when you start the engine.

reconnect the coil, then hook-up you volt/ohm meter and start the car.

you should see the charging system voltage rise to about 13.6V to 14.2V.

the charging system naturally fluxuates..........

hope this helps.

[davep]

I'm still waiting to hear the results of the tests I suggested. Do the basics first, that is the voltage drops through the current paths.

Output of the alternator at idle is very low. You can't charge a battery at idle. You need 1500 RPM at least.

[nycchef]

the d+ terminal and the d field terminal are both on the relay board. i think you jump them together with the vr in then remove the vr and check to see if the charge going to the battery goes up to 16 or 17. do this quickly or you can cook the battery. again i'm new at this also so confirm with some others before trying. there is a diagram in my alternator woes post from 6/6. it shows the relay board in detail.

[rhodyguy]

with lights and what not on, every car i know of experiences some idle drop. i think dave's does it even with an upgraded alt. for night running i just turn an idle screw up to maintain a reasonable engine speed.

k

[dinomium]

I added a ground from the post to the fan shroud. Make sure the VR is a Bosch, I have had good FLAPS brand vrs not be up to the task. And not just in Porsches, Ford and Toyotas both want OEM VR, go figure...

The real key here is to go SLOWLY and change one thing at a time. Start at the basics and work your way up.

I installed a white board in my garage to map out flow charts for problem solving!

[Dr. Roger]

a white board is a (great+brilliant=) grilliant idea!

dave p is right.
start with the basics... then work your way up.

914's have a reputation for poor grounds. reputations get built on past history.... check the grounds first. (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/agree.gif)

[rjames]

Check the ground circuit: measure the voltage difference between the negative post on the battery and the fan shroud. The alternator grounds through its case to the fan shroud, then the engine, transmission, up the ground strap and through the body to the battery strap and then the post. That is a long path with lots of connections. If you get much of a voltage difference, then start checking the ground straps.

Voltage is the same at bothe the battery and the fan shroud. Voltage alo measures the same at the cable ends as it does at the battery terminals: about 12.5 at idle. Measured for resistance at the ground straps both at the battery and at the transmission. Zero resistance. Removed them both anyway and gave them a good cleaning.

Voltage regulator is a new Bosch unit, although I still have the old non-bosch unit that came with the car. No difference between the two. I have 2 relay boards to play with- the one currently in the car, and another used one that I will test tonight. Other things I will try tonight:

plugging in the alternator directly into the voltage regulator. (this works, right?)
and/or shorting the D+ & D terminals on the relay board. Although a little leary as I don't wan't to fry my battery.

also maybe grounding the coil as suggested by Dr. Roger to see if the alternator kicks in when starting the car.


I drove around last night for about 30 minutes at high rpms after cleaning the ground straps- when I got home the voltage was still 12.5ish at idle.

[davep]

I suspect that removing the VR from the relay board removes the connection from the alternator light that is used to kickstart the battery. I'd have to check the circuit diagram to see where it connects.

There should be a voltage difference between the fan housing and the battery post, even if it is only a 10th of a volt.