Check Main Circuit Breakers; Check Load Voltage & Frequency; Check Load Watts & Amperage - Guardian 4700 Repair Manual

Section 7
DIAGNOSTIC TESTS
the Rotor shaft). The meter should read "infinity".
RESULTS:
1. Replace the Rotor if it fails the test.
2. If Rotor checks good, perform "Insulation Resistance Test," on
Page 11.
POSITIVE (+)
TEST LEAD
Figure 7-8. – Rotor Assembly
TEST 12 - CHECK MAIN CIRCUIT BREAKER
DISCUSSION:
The main circuit breaker on the generator panel must
be closed or no output to the load will be available. A
defective breaker may not be able to pass current
even though it is in the "ON" position.
11
33
CB1
T1
A. Schematic
Figure 7-9. – Main Breaker (Typical)
PROCEDURE:
Set the coach main breaker to it's "OFF" position.
Check that the appropriate main breaker on the gen-
erator panel is set to its "ON" (closed) position. Set a
VOM to measure resistance and use it to check for
"continuity" across the breaker terminals.
Page 36
RESULTS:
1. If breaker is "ON" and continuity is measured, go to Test 3.
2. If breaker is "OFF", reset to the "ON" position and check
3. If breaker is "ON" and continuity is NOT measured, replace
DISCUSSION:
If engine speed appears to drop off excessively when
electrical loads are applied to the generator, the load
voltage and frequency should be checked.
PROCEDURE:
Perform this test in the same manner as Test 1, but
apply a load to the generator equal to its rated capac-
ity. With load applied check voltage and frequency.
Frequency should not drop below about 58 Hertz with
the load applied.
Voltage should not drop below about 115 VAC with
load applied.
RESULTS:
1. If voltage and/or frequency droop excessively when the load is
2. If load voltage and frequency are within limits, end tests.
TEST 14- CHECK LOAD WATTS & AMPERAGE
DISCUSSION:
This test will determine if the generator's rated
wattage/amperage capacity has been exceeded.
Continuous electrical loading should not be greater
than the unit's rated capacity.
PROCEDURE:
Add up the wattages or amperages of all loads pow-
B. Pictorial
ered by the generator at one time. If desired, a clamp-
on ammeter may be used to measure current flow.
See "Measuring Current" on Page 14.
RESULTS:
1. If the unit is overloaded, reduce the load.
2. If load is within limits, but frequency and voltage still drop
for AC output.
the defective circuit breaker.
TEST 13- CHECK LOAD VOLTAGE &
FREQUENCY
applied, go to Test 14.
excessively, complete Test 2, "Check/Adjust Engine
Governor". If governor adjustment does not correct the prob-
lem, go to Problem 8.