Replies:
From
Scotty:
Well
first things first : Check the cables for corrosion and looseness check
where the output lug is for corrosion and looseness most of the time
that happened to me it has been a bad voltage regulator a cheap and
easy part to fix . go down to the local auto parts store and get an
inexpensive volt/ohm meter and check out put at the alternator it should
be around 13 to 14.5 volts if not check the connection from the volt
regulator to the alternator clean it and then recheck voltage if still
low take the alternator off and go to the local parts place like PEPBOYS,
NAPA, or some such.. they will test the alt for free and if checks cool
get a voltage regulator ..if this doesn't solve it then you have a serious
problem like a partial short to ground when the engine is in gear ..then
its a process of rooting around the electricals until you find it.
From
Richard:
The
best check for alternator/regulator problems is any voltmeter you have
laying around, or can get hold of. Put it across the battery and measure
the voltage without the engine running. After starting the engine the
voltage should increase slightly to about 12.5vdc. Next turn on the
headlights, if the charging system is working, the voltage should jump
to about 14.5 vdc. Without a meter and in the dark: Set the engine idle
to the correct speed and turn on the headlights. If the lights are sort
of dim while idling in gear, and get brighter as you increase engine
speed (slightly): bad alternator. When you replace the alternator, replace
the regulator. Trust me. While your under the hood, check this: on the
right side wheel house is a 10 or 12 pin connector for the engine wiring
harness, which includes the field leads for the alternator. The contacts
are generally green w/ corrosion. Check the bulkhead disconnects (firewall,
below power booster) while your at it. In fact, check all the connectors
under the hood for corrosion and/or loose/frayed connections. I'm sure
you'll find several. Cracked battery terminals wouldn't be a surprise
either. One last thing, the 100 amp alternator uses rubber insulating
boots in the mounting bolts and has an external ground wire (housing
should not be grounded). The insulators crumble over time, and the ground
wire often breaks.
From
Bill:
I
have had similar problems in the past and it has been either a wiring
short or problem or voltage regulator. Not real familiar with a 75 but
I think the voltage regulator is built into the alternator. If you have
a volt meter you could check the output. The easiest way is to go to
a service station that can check your whole charging system with their
equipment. Most will do this for free or very nominal cost.
From
Frank:
Well,
lets first start with some background. The gauge set in the 75-78 Imperial
/ NYB consists of gauges for temp, charge/discharge, and fuel. Within
each gauge is a LED. The LED for temp and fuel is slaved to the gauge,
so that when high temperature or low fuel is reached the LED confirms
the reading. The LED within the alternator gauge is a bit different.
It does not indicate discharging, but rather low battery voltage. I
just double checked the factory manual, and unfortunately, it only says
that the LED illuminates when the voltage falls below "a pre-determined
point." I would estimate somewhere around 11.5V.
OK,
so what you have is probably low system voltage and some charging, since
you don't mention the need to jump-start the car, or charge the battery
frequently. Thus, the problem you most likely have is either: 1) Worn
field brushes that are not transferring enough current to the alternator
field to sufficiently charge the battery 2) Some shorted or open rectifiers
inside of the alternator.
I'm
betting on #2 since the ammeter does not indicate discharge consistently.
I'll also bet that you are hearing quite a bit of alternator whine in
your car's stereo system. I always knew it was time for new rectifiers
when the battery seemed weak, the ammeter stayed kind of centered, and
there was a bit more noise in the stereo!
What
to do? Your car probably uses the 100 amp alternator. This unit has
12 rectifiers arranged in 2 sets of 6. One set for positive and one
for negative. You could go out and buy a rebuilt alternator. But if
the bearing in your alternator are still good, you can just replace
the rectifiers. Why? It is MUCH CHEAPER to replace the rectifiers than
to get a rebuilt alternator. A few months ago, the alternator got weak
in my car. (This one is not a Chrysler product, but an alternator is
an alternator.) Poked around with a DVM and found that the regulator
was regulating, but the alternator was not putting out much current.
Pulled the alternator and put it on a solid bench and spun the pulley.
The armature spun easily and quietly, so the bearing were OK. Called
around and found rebuilts at the dealer for $170ish; auto parts had
them for $130ish. Called a starter generator rebuilder and bought the
rectifiers for $25! (Most auto parts can order them, too.) Figured I'd
splurge and bought brushes for $4. So, if I were you, I'd fix what I
have and pocket the $100.
This
really is a simple service job and is darn hard to goof up. I've actually
done it in under an hour WITHOUT getting dirty. (Of course my car is
still pretty clean under the hood since it only 7 years old and has
just 143K miles.)
Remove
the battery ground cable.
Pull
the alternator and remove the wires.
Remove
the brushes (white plastic carrier on the back of the unit. It is where
the two field (blue and green) wires attach.) The case should be stamped
"FLD"
Remove
the screws that hold the two halves together.
Separate
the two shells. There is a slot to insert a screwdriver and pry a bit
to get the process started.
Keep
the stator with the back side of the alternator. (The stator is a ring
that looks like a stack of metal rings with heavy wiring running through
it.)
The
wiring of the stator is connected to the rectifiers. There are three
nuts that hold the wires to terminals on the rectifiers.
Remove
the nuts that hold the stator wiring.
Lift
the entire stator free. Don't pull or bend the wires unnecessarily!
Everything should just lift off and the wire should just slide up off
the rectifier terminals.
Using
a VOM, or a DVM (CAUTION, ONLY USE A DVM THAT HAS A DIODE TEST POSITION!)
check the rectifiers. Current should pass in only one direction. The
negative rectifiers are near the periphery of the case.
The
positive ones are near the center. If you get continuity in both directions,
you have a shorted rectifier and must replace that set. If you get no
continuity in either direction, you have an open rectifier and must
replace that set.
Remove
the screws for the bad set and replace. Reassemble the alternator in
reverse order of disassembly. Oh, when reinstalling the brushes, the
long terminal one goes on the bottom and the short terminal goes on
the top. (Assuming that you have the alternator positioned with the
pulley down.)
From
Dick:
The
red light is warning you that your alternator is not putting out the
normal full charge. It is working, but not up to snuff. The red light
should not come on at idle, especially if your idle is set high.
Take
your alternator to your local el-cheapo auto parts place and get a rebuilt
(make sure you get the right amperage, it will be in your shop manual-electrical
specifications section, and is probably a 63 AMP unit). Most of the
ones on the shelf will be 45 AMP units, which will work in a pinch,
but your car needs the extra capacity because of all the electrical
gee-gaws on it, especially in the winter.
Your
existing alternator probably has two burned out rectifier diodes, and
one still working, giving it a maximum output of either 15 or 21 AMPs,
depending on which size it is. You cannot tell by looking at the size
of the case, but if you look very carefully you will see the capacity
stamped into the rear housing of the alternator on the outer circular
surface. It is usually something like "45A" or "63A"
or the like.
I'm
not sure which of the many electrical testing devised you are referring
to, but I would advise that you get a VOM and a High current magnetic
coupled type of current meter for your tool box. You will use them all
the time, and no, they are not difficult to understand.
The
high current meter is useful for checking starter draw (usually on the
400 AMP) scale, and alternator output (usually on the 50 AMP scale),
and is used by merely holding it in close proximity to the wire through
which the current is flowing. Instructions for positioning the meter
and avoiding interfering metal objects will come with the meter, or
if they do not, I can help you with that.
The
VOM is used for a multitude of tests, it will measure DC and AC voltages
from a few hundredths of a volt to 1000 volts. It will measure resistance
from 1 OHM to Mega-OHMS, and it will measure current from tenths of
amperes to 10 AMPs. They are available from Radio Shack for under $50,
and will save you one hundred times that much in not having to depend
on the local repair guy to figure out what is going on with your car's
electrical system. It will come with very complete instructions.
You
need to understand only this:
1.
Voltage ("E"), Current ("I"), and resistance ("R")
are related by this simple equation...........E=IR.
2.
Power ("W") can be computed by taking W=EI.
3.
Your battery stores power (never mind how) in the form of available
current at 12 volts.
4.
Your battery stores energy in the form of power (12 X AMPS) times the
length of time for which it can deliver such power. Thus the rating
on batteries used to be in "ampere-hours" and a typical rating
for a car like yours would be 75 AH. Unfortunately, lately battery vendors
have begun hiding the AH rating in their catalogs, and selling batteries
by CCA ratings, which is cold cranking amps. These are also important,
but make identifying the largest capacity battery for a price difficult
to identify, you have to look in the electrical spec. to find it. Your
owner's manual tells you what was standard in your car when it was new.
Often in lesser cars, larger capacity batteries are an option, but an
Imperial would automatically have the largest capacity battery (of the
required physical size) available
You
can play around with this information in various ways. For instance,
if you have a 75 AH battery that is completely discharged, and an alternator
that is putting out 63 A, it will recharge the battery in about 1 1/2
hours, plus some additional time to account for inefficiencies like
heating effects, but say 2 hours to be sure. If your alternator is only
capable of 15 A, and you run your starter at say 300A to start the car
for say 10 seconds, once the car starts, it will take the alternator
200 to 300 seconds (5 minutes) to bring the battery back to the state
of charge it was in before you started the engine. And if you drive
off with your lights on, which take about 15 A on bright, leaving nothing
for the battery, you will never bring the battery back to full charge.
That's why you need a big alternator on an Imperial.
