Scrub System
43
Service Manual – Clarke CA30 20B and 17E
Start Relay Troubleshooting Voltage Readings
Most brush motor troubleshooting can be completed by simple observations. The table below provides
further information if confirmation is required, or to isolate the cause of similar symptoms. As with other
troubleshooting observations, these measurements should be preformed for no more
than a couple seconds at a time, and time should be given to allow the motor windings
to cool between measurements.
Warning!
Risk of electrocution. These measurements require measurement of
voltages with the system powered and active. Unplug the machine
while setting up the test probes, and stay clear of the probes and
system wiring when the machine is powered.
V
O
= Voltage Off, V
S
= Voltage Startup, V
R
= Voltage Running
Normal Operation
Terminals
V
O
V
S
V
R
Scope
Comment
2-4
1.0
↑
239
2-5
0
↑
203
2-1
0
0
239
Shorted, then Jumps after relay opens
1-4
0
69
0
Building start capacitor voltage, then disconnected
1-5
0.7
15
1.3
Building start capacitor voltage, then disconnected
4-5
0
120
120
Normal line voltage
Failed Start Capacitor (Never Reaches Run Speed, Relay Never Opens)
Terminals
V
O
V
S
V
R
Scope
Comment
2-4
0
105
---
2-5
0
21
---
2-1
0
0
---
Shorted by relay contacts, relay never opens
1-4
0
105
---
Same as 2-4
1-5
0
21
---
Same as 2-5
4-5
0
95
---
Voltage drop in power cord due to high amperage
Failed Run Capacitor (Relay Opens Normal)
Terminals
V
O
V
S
V
R
Scope
Comment
2-4
0
↑
191
Slight stutter as relay opens
2-5
0
↑
140
Slight stutter as relay opens
2-1
0
→
191
Shorted, then Jumps after relay opens
1-4
0
120
0
Same as 2-4 until relay opens
1-5
0
↑
120
4-5
0
120
120
Same as normal operation
Failed Start Relay (Start Circuit Never Disengages)
Terminals
V
O
V
S
V
R
Scope
Comment
2-4
0
↑
170
The motor starts normally, but then enters an over-
powered condition when the starter doesn’t disengage.
2-5
0
↑
220
2
1
4
5
