MAINTENANCE OF M939 SERIES VEHICLES - OD1661 - LESSON 1/TASK 2
d.
Cooling System Troubleshooting.
In the following paragraphs we
will follow SGT Bowers as he troubleshoots the cooling system for the
malfunction ENGINE DOES NOT REACH NORMAL OPERATING TEMPERATURE
(ACCORDING TO COOLANT TEMPERATURE GAGE).
For the purposes of this
example SGT Bowers will find that the water temperature sending unit
is defective and needs to be replaced.
SGT Bowers first reads DA Form 2404 and talks to the operator. After
this has been done, SGT Bowers reads through the troubleshooting
procedure to determine what tools will be required.
For this
malfunction SGT Bowers will need a mechanic's general toolbox and a
STE/ICE test set.
After the necessary tools have been gathered together, SGT Bowers
ensures that the vehicle is configured according to the procedures
contained in paragraphs 3a(1) thru 3a(5) on page 34.
Prior to beginning the actual troubleshooting procedures, SGT Bowers
is directed to perform No-Go test 31 if a STE/ICE is available. For
the purposes of this subcourse a STE/ICE was available. Also it is
assumed that the test set has already been connected.
After the test set has been connected to the vehicle, SGT Bowers
begins No-Go test 31. He is directed to install the current probe.
Step 1. In this step the current probe is installed.
This is done
by connecting P1 of the test probe cable to W2 of J4
on the VTM.
After the P1 is connected, he shorts the red and
black leads
together. Now he is directed to perform the test probe
cable offset
procedures.
Step 2.
In this step SGT Bowers dials 89 into the TEST SELECT
switches.
He then presses and holds the TEST button until the CAL
message appears on the display.
After this message is received, he
releases the TEST button and waits for the offset value to appear on
the display.
The offset value should be between -225 and +225.
Since it is within these limits, SGT Bowers is directed to isolate
the fault to the sending unit or the gage.
Step 3. In this step, SGT Bowers first removes the wire from the temperature
sending unit on the vehicle.
After this has been done he connects the
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