Test 14 - Check Rotor Assembly; Test 15 - Check Load Voltage & Frequency; Test 16 - Check Load Watts & Amperage - Generac Power Systems 4451 & 4986 Repair Manual

section 6
Diagnostic tests
BRUSHES
Figure 6-21. – Brush Location
2. Remove Wire 4 from the positive (+) brush terminal.
3. Remove the ground wire (0) from the negative (-) brush.
4. Remove the brush holder, with brushes.
5. Inspect the brushes for excessive wear, damage, cracks, chip-
ping, etc.
6. Inspect the brush holder, replace if damaged.
7. Inspect the slip rings.
a. If slip rings appear dull or tarnished they may be
cleaned and polished with fine sandpaper. DO
NOT USE ANY METALLIC GRIT TO CLEAN
SLIP RINGS. (A 400 grit wet sandpaper is rec-
ommended).
b. After cleaning slip rings, blow away any sandpa-
per residue.
RESULTS:
1. Replace bad brushes. Clean slip rings, if necessary.
2. If brushes and rings are good, go to Test 14.

TEST 14 - CHECk ROTOR ASSEMbLY

PROCEDURE:
Gain access to the brushes and slip rings. Disconnect
Wire 4 and Wire 0 from their respective brushes and
remove the brush holder. Then, test the Rotor as fol-
lows:
1. Set a voltmeter to measure resistance.
2. Connect the positive (+) meter test lead to the positive (+) slip
ring (nearest the Rotor bearing). Connect the common (-) test
lead to the negative (-) slip ring. Read the resistance of the
Rotor windings, in OHMS.
ROTOR RESISTANCE
MoDel:
004451-0 004986-0
004582-0,1 004987-0 005209-0
004582-2 004987-1
004583-0 005308-0
Page 46
* Resistance values in ohms at 20° C. (68° F.). Actual readings
may vary depending on ambient temperature. A tolerance of plus
or minus 5% is allowed.
3. Connect the positive (+) meter test lead to the positive (+) slip
RESULTS:
1. Replace the Rotor if it fails the test.
2. If Rotor checks good, perform "Rotor Insulation Resistance
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 59 Hertz with
the load applied.
Voltage should not drop below about 235 VAC with
load applied.
RESULTS:
1. If voltage and/or frequency drop excessively when the load is
2. If load voltage and frequency are within limits, end tests.
PROCEDURE:
*
Add up the wattages or amperages of all loads pow-
oHMs
ered by the generator at one time. If desired, a clamp-
7.01Ω
on ammeter may be used to measure current flow.
See "Measuring Current" on Page 7.
7.71Ω
13.1Ω
RESULTS:
14.2Ω
1. If the unit is overloaded, reduce the load.
ring, the common (-) test lead to a clean frame ground (such as
the Rotor shaft). The meter should read INFINITY.
Test," on Page 15.
POSITIVE (+)
TEST LEAD
Figure 6-22. – Testing at Slip Rings
TEST 15 - CHECk LOAd VOLTAgE &
FREqUENCY
applied, go to Test 16.
TEST 16 - CHECk LOAd WATTS & AMPERAgE