ST-70 — PARTS & OPERATION MANUAL — REV. #4 (05/29/07) — PAGE 87
ST-70 — SERVICE INFORMATION
Electrical System
Proximity switches
The proximity is a normally open switch. The proximity develops
a radio frequency, which is emitted from the face of the proximity
switch. As the hydraulic drive cylinder piston passes through
the radio frequency, the circuit closes and a signal is sent to the
pilot cycle valve. This valve cycles the pump and causes the
concrete to flow.
This proximity switch is designed to work at hydraulic pressures
of 5000 PSI and oil temperatures of 250
o
Fahrenheit.
Problem
At the completion of a pumping stroke the pumping pressure
gauge indicates high pressure and the pump doesn’t cycle.
If the emergency cycle switch doesn’t cycle the pump it may
well be a problem with the K-4 relay. A quick check for a problem
with the K-4 relay is to use a hot jumper wire. Connect (jumper
wire) to terminals #35 and #36 on terminal block #1. When
contact is made between these two terminals and the pump
cycles. This would indicate that you have a faulty K-4 relay.
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Problem
When starter switch is activated and nothing occurs.
Problem
Hatz engine will not continue to run after key is released.
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Problem
Hatz engine will not start.
Problem
Engine runs, no power to circuits #32-47.
Problem
Hatz engine will not increase Rpm’s when the pump is turned
on.
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Problem
The pump will not reverse in Remote Control.
Problem
Engine oil pressure light will not go out.
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Battery charge light won’t turn off.
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