ELECTRICAL SYSTEM
RT765E-2 SERVICE MANUAL
3-10
Published 9-04-2014, Control # 422-08
Engine Off Tests
Batteries
Disconnect the batteries and test each battery individually.
Check the electrolyte level, if possible
Using the multimeter, measure the voltage across the
terminals. If the voltage is 12.4 V or above, perform the
following load test. If the voltage is lower than 12.4 V,
recharge the battery(s) before performing the load test.
Load Test
1.
Refer to the load tester manual for instructions on
performing the load test.
2.
Connect the load tester to one battery and test.
3.
Connect the tester to the second battery and test.
4.
Connect the tester to the third battery and test.
Proceed to the next test if the batteries passed the load test.
Replace a battery if it failed the load test.
Voltage at Alternator
Measure voltage from alternator case to output terminal. The
meter should read 12.6V or above.
Battery Drain
With a DC ammeter capable of measuring milliamps, and a
10 amp capability, perform the following test:
1.
Make sure the ignition key is off.
2.
Set the meter to the 10 amp position.
3.
Check for a drain by disconnecting the negative battery
terminals and measuring between the battery post and
the cable with the ammeter.
This reading should not be more than 80 milliamps (.08 A)
with all accessories OFF. A higher reading indicates
something is draining the batteries and the system must be
troubleshot and repaired.
Engine On Tests
Output Voltage Test
1.
Connect multimeter to negative and positive battery
terminals.
2.
Connect ammeter clamp around output wire of
alternator to the batteries.
3.
Start engine and increase speed to 2000 rpm.
With fully charged batteries and no loads on the system, the
multimeter should read 14 V.
Maximum Amperage Test
1.
Connect an adjustable carbon pile load tester to the
batteries’ positive and negative cables.
2.
Run engine at 2000 rpm.
3.
Adjust carbon pile to obtain maximum amperage while
not letting voltage fall below 13 volts.
4.
Amperage should be within 10 to 15 amps of alternator
rating; this alternator is rated at 145 A, so the meter
should read 130 A to 135 A.
NOTE:
If the correct readings were not obtained in the
Engine On Tests, perform the following two tests.
Voltage Drop Test
Positive Side
1.
Set the multimeter to the 2 volt range.
2.
Connect the positive (
+
) lead to the alternator output
terminal and the negative (
–) lead to the battery positive
terminal or post. Do not connect the meter to the battery
cable.
3.
Run the engine at 2000 rpm.
4.
Load system with carbon pile load or lights and heater
blower.
Allowable drop is 0.2 to 0.5 volts. Higher voltage drop
indicates loose, corroded, or broken connections.
Negative Side
1.
Set the multimeter to the 2 volt range.
2.
Connect the negative (
–) lead to alternator case and the
positive (
+
) lead to the battery negative terminal or post.
Do not connect the meter to the battery cable.
3.
Run the engine at 2000 RPM.
4.
Load system with carbon pile load or lights and heater
blower.
Allowable drop is 0.1 to 0.3 volts. Higher voltage drop
indicates loose, corroded, or broken connections.
DANGER
Do not smoke or allow sparks or open flame near
batteries, they can explode.
When working with batteries always wear protective
clothing, gloves and eye protection. Batteries contain
corrosive liquids that can burn skin and eyes and
destroy clothing.
Remove rings, watches or other jewelry before working
with batteries. A battery can produce a short-circuit
current high enough to weld a ring, or the like, to metal
causing severe burns
Reference Only
