Battery Quirks

[Brian_L]

Hi all.

I'm new here, and not the biggest car guy (I'm a computer geek ), but I have been having a strange problem. I'll describe, but you'll have to forgive if some terms sound a little "primal".

Anyway, I own a 1994 Regal 3.8, and not too long ago, the ABS light kept coming on. The car also started having troubles starting. It often took 10+ tries to get it going. Got the codes checked by a great mechanic, and he told me the reason the ABS light was coming on was low voltage. So after checking some more, he told me the battery was just about dead, and the alternator almost completely seized. So I got both replaced and I thought that was the end of my troubles.

But the next day, as I was driving, the voltage gage just dropped in the red, stayed there for a few seconds, and came back up around 14-15. It did it again a few minutes later. When I started the car again a few minutes later, the voltage gage never went up, stayed in the low red for about 3-4 seconds, then I heard a "cranking" noise (here come the primal terms) and then the gage went up to normal.

When I stop at lights, the gage goes down to about 9-10, and comes right back up when I get going again. I am still having troubles to start the car (often takes 3-4 tries), went to the mechanic again, but of course, the car started just fine every time he tried. He checked the battery, and it's fine, and it charges normally.

A few times now when I try to start the car, the "Service Engine Soon" light comes on when the voltage gage doesn't go up right away. After the cranking noise, the gage goes up, but the light stays on. I restart the car, and everything is just fine. I'll go get the codes read on Monday, but I'd like to know if anyone has any suggestions.

Thanks.

[MagicRat]

It sounds as if you have something that intermittently draws large amounts of electricty from the cars electrical system.

I suspect either a bare wire, is shorting out on the chassis somewhere. Its most likely a fat wire , like the kind going to the starter motor. Otherwise that much power would melt a thinner wire.

Otherwise it could be the starter motor solinoid and or starter motor are shorting out.

Your alternator puts out about 14 volts when the engine is running. The battery produces about 12 volts, on its own. So even if the car is not running, there should be at least 12 volts in the electrical system.

The only way it will suddenly drop to 9 volts is with a huge electrical drain on the system.
I would suggest not driving your car until this is fixed. Its not safe (electrical fire hazard)

[KC Ron Carter]

The voltage regulator will have a set of carbon brushes.

This is for a Bosch BMW alternator but all are almost the same.

They can wear into a grooved pattern and the impact of driving can make them vibrate out of the normal groove.

Since the regulator has to increase output to jump the gap it does.

You can clean up the slider rings with abrasive paper.

You can get the brushes as a separate part requiring soldering skills or you can get a Regulator brush assembly for $70.

Some instruction for changing:

It is a very touchy installation and about 5% of the installation end in the ground link bent and the alternator not functional.

You can remove correct and reinstall the regulator.

The output must be 14.25 or higher on a Volt Ohm Meter not the dash gauge.

Some hints on the regulator change.

Replacing Alternator Regulator

For those who work on their cars and have not had alternator problems, here is a simple action that should save you down-time and significant costs.

Most alternators on German cars fail due to brushes wearing down (as they are supposed to) between 150k and 200K miles. Brush replacement is very easy -- it should not take over 20 min. and the brushes are attached to a new regulator.

To replace regulator assembly -- back of alternator held in place with two straight slot headed screws. This has a round transistor mounted on the outside on Bosch alternators -- the other type is similar but uses different brushes. Pop the regulator out, after removing the screws.

Fitting the regulator back is simple, but you must install it starting at an angle, to assure that the brushes compress when the regulator is flush with the alternator and the screws are tightened.
You are now ready for 200K miles of alternator life.



Later,

[MagicRat]

Originally Posted by KC Ron Carter

The voltage regulator will have a set of carbon brushes.

This is for a Bosch BMW alternator but all are almost the same.

They can wear into a grooved pattern and the impact of driving can make them vibrate out of the normal groove.

Since the regulator has to increase output to jump the gap it does.

You can clean up the slider rings with abrasive paper.

You can get the brushes as a separate part requiring soldering skills or you can get a Regulator brush assembly for $70.

Some instruction for changing:

It is a very touchy installation and about 5% of the installation end in the ground link bent and the alternator not functional.

You can remove correct and reinstall the regulator.

The output must be 14.25 or higher on a Volt Ohm Meter not the dash gauge.

Some hints on the regulator change.

Replacing Alternator Regulator

For those who work on their cars and have not had alternator problems, here is a simple action that should save you down-time and significant costs.

Most alternators on German cars fail due to brushes wearing down (as they are supposed to) between 150k and 200K miles. Brush replacement is very easy -- it should not take over 20 min. and the brushes are attached to a new regulator.

To replace regulator assembly -- back of alternator held in place with two straight slot headed screws. This has a round transistor mounted on the outside on Bosch alternators -- the other type is similar but uses different brushes. Pop the regulator out, after removing the screws.

Fitting the regulator back is simple, but you must install it starting at an angle, to assure that the brushes compress when the regulator is flush with the alternator and the screws are tightened.
You are now ready for 200K miles of alternator life.



Later,

Thats great KC, but he said he already got a new alternator and still has a problem.
Also GM cars use an electronic voltage regulator. They have no brushes and are service by replacing solid state electrical components. You describe a mechanical regulator which has not been used in American cars (at least Ford and GM) since the early 1970's

[MagicRat]

I should add the GM voltage regulator is built into the alternator.
Get a new alternator and you get a new voltage regulator

[Brian_L]

I can't stop using my car, but I am limiting the number of uses. And I had another development today:

I tried to start the car, but the engine never started, but instead, I got a fast beeping sound (same sound I get if the key is in the ignition and I open the door, only faster). And I I turn the key to "battery", I would get a fast drumming sound coming from the fuse box under the hood. Any ideas? I am going to see my mechanic first thing tomorrow, but any ideas would be welcome.

After letting it rest a few minutes, it started just fine...

[MagicRat]

Brian, the drumming sound is likely an electrical relay or circuit breaker that is cycling on and off.
This confirms my electrical short theory, that is, the relay or breaker is protecting a short circuit from overloading, and subsequently burning down your car.
Be careful and see a mechanic immediatly. Most problems like this are somewhat difficult to find but easy to fix,

[Brian_L]

Well, it was a short, but simply a loose wire and some corrosion between the battery and the fuse box. Something about a "post"? All's well that ends well (let's hope).

Thanks for the help.

[MagicRat]

Likely a battery terminal post. They corrode and are less likely to make a good contact over time, especially the terminals that are on the top (not the side) of the battery. Have your mechanic clean them up, perhaps once or twice a year. It just takes a minute to unbolt it and lean it up with a small wire brush