Been there, fixed that. What follows applies directly to a generator regulator, and may be quite different for an alternator. I found it far more cost effective to repair, rather than replace. Regulators are rarely bad, only a little tired - unfortunately they are either expensive or hard to find, now that most folks have alternators. Sorry to be wordy, but short of substitution, the only good way to work on a SYSTEM like this is SYSTEMATICALLY.
The things which can happen in the charging SYSTEM which
will prevent the battery from charging are:
++ Excessive resistance in wiring, especially terminals.
++ Excessive resistance in regulator contacts.
++ A worn-out circuit breaker exhibiting excess resistance.
++ A poor connection on the engine-to airframe ground strap.
++ A worn out generator with bad commutator or brushes.
++ A bad battery. Sulfated (high resistance).
If you feel comfortable around electricity and are careful,
you can troubleshoot and repair. Remember that shorting the
battery can vaporize parts of the tool you are using and
throw molten metal around; the voltage won't hurt, but
molten metal and battery acid are no fun. There is a
step-by-step procedure which will probably either fix or at
least point out what is wrong.
To attack the system you will need a known accurate digital
voltmeter. They cost as little as $15, so get one. Next,
you will need clip leads so that you can attach the meter to
various parts of the circuitry without holding test probes
in place. Lastly, you will need a relay-contact-file; these
used to be common when everyone had generators and
distributors with contacts in their cars; although the books
say no, I've never had problems using 400 grit sandpaper and
clean compressed air for cleaning.
What to do:
++ It is important to do a thorough visual check, at the
main breaker as well as all heavy wiring between generator,
regulator, battery, and airframe.
++ Next, it is important to assure that the battery is OK.
If it will take (and maintain) a charge from a separate
charger, it is probably OK. A second check is to measure
its voltage right on the battery terminals with the charging
system running. At a high enough RPM (1500+), the voltage
should be 14.0 to 14.5 (this varies a little with ambient
temperature); the target is usually 14.4 at around 65
degrees. If the voltage is higher, you have a bad battery;
if lower, a bad charging system.
++ Next, measure the voltage between the Regulator BATT
terminal and the airframe under the same conditions. If the
voltage is more than two tenths of a volt higher at this
point than it was at the battery, there is too much
resistance somewhere aft of the firewall.
++ If the problem appears to be aft of the firewall, use the
voltmeter to measure VOLTAGE DROPS from point-to-point.
Alternately, you can use a heavy jumper lead or a substitute
part to short (across the terminals) out or substitute for
the BREAKERS.
++ If the problem is forward of the firewall, it helps to
next eliminate the generator as the source. Remove the wire
from the REGULATOR FIELD terminal. Short this wire to the
airframe with a jumper lead. DO NOT SHORT THE TERMINAL TO
GROUND - THIS WILL SEVERELY DAMAGE SOME REGULATORS. Run the
engine again at 1500+ and see if the ammeter responds (and
the battery terminal voltage rises to 14.2+ volts. If the
battery does not charge at this point, the generator is
PROBABLY bad (you did check the wiring, didn't you?). Tying
the generator's field lead to ground produces maximum charge
rate!
++ One more check on the generator! If the aircraft has not
been used for a long period, it is possible that the
generator has lost its residual magnetism. To check this,
CAREFULLY (safety glasses are a good idea here) turn on the
MAIN and GENERATOR BREAKERS and touch a heavy jumper lead
for a fraction of a second between the REGULATOR ALT and
BATT terminals. This should produce a spark. Then, once
again see if the battery will charge.
++ If all the above has failed, only then disconnect the
battery and open the Regulator cover. A normal regulator
has three relays - one or two will have only a pair of
contacts. Examine the contacts with a magnifier and strong
light. Using your file, carefully BURNISH the contacts - the
idea here is not to remove lots of metal, but only to clean
the contacts. Clean them by drawing a piece of clean paper
(possibly saturated with acetone or lacquer thinner) across
them. DO NOT CHANGE TENSION ON SPRINGS OR CHANGE THE GAPS.
Try the charging system again.
++ If you have exhausted all avenues at this point, an auto
electric shop can test and calibrate the regulator off the
plane.
------
I had a charging problem which turned out to be two things
=> the regulator case was not grounded reliably; there is a
small ground terminal which was not connected and the
regulator was grounded only by honking down on the mounting
screws so that the isolating grommet was squeezed to the
point it wasn't isolating any more. The second problem was
that the GENERATOR breaker was mechanically worn out and
high enough resistance that there was a large voltage drop
across it.
------
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David Smoler | __ |
|==/__ยค_\==|
*==========|==| () |==|===========*
Alon A-2 | \____/ | N6359V
s/n A35 () () () based at RHV
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Steven Lewis wrote:
>
> I may be having problems with my voltage regulator
>
> 1) Is there a way to test this???
> 2) I understand that an automotive regulator will work there - which
kind and
> has anyone tried this???
> ==============================================================
> LordJoe - Java Training and Consulting
> http://www.LordJoe.com
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