Using 9S9102 Thermistor Thermometer Group{0651} Caterpillar

The Thermistor Thermometer is used in analyzing overheating problems. It is capable of reading cooling, transmission, and hydraulic system temperatures.

The Thermistor Thermometer is contained in a portable two-section box. One section is the temperature read-out, 32° - 300°F (0-150°C), with six plug in jacks and a selector switch for each jack. The other, removable, section provides storage space for accessories. The serviceable parts of the group are: four 20639 Adapters (1), 3B7721 Bushing (2), 8B1931 Bushing (3), four 4M5317 Bushings (4), 3S8684 Fitting (5), two 9S9106 Angle Adapters (6), 9S9103 Probe (7), two 9S9104 Probes (8), 9S9105 Probe (9), 5P2717 Probe (10), 5P2372 Cable (11) (High Temperature) and 9S9107 Cable (12). NOTE: Use 9S9107 Cable (12) in temperature areas of -4°F to +176°F (20°C to +80°C) only. In areas where the temperature is beyond this range, use 5P2372 Cable (11) (High Temperature). Probes of four different lengths are provided to adapt to various requirements. Only the 9S9105 Probe (9) and 5P2717 Probe (10) are to be used with the self-sealing probe adapter groups. The probes can withstand pressures in excess of 4000 PSI (27500 kPa) without damage; therefore, they can be used for checking transmission and hydraulic system temperatures. The adapters provide for a variation of probe penetration into an opening. The reducing bushings and the fitting adapt the probes to different size openings. The two angle adapters provide a 90 degree connection and a 360 degree swivel action between the probe and cable assembly. The four cables are color coded at each end for identification between the probe end and plug-in end on the meter. Additional electronic components can be ordered directly from Flo-Tech Inc.; see the section (Parts Information) on Page 23 of this instruction.

Using 5P2720, 5P2725 And 5P3591 Probe Adapters

The probe adapters can be used as follows: in fuel and cooling systems ² to a maximum pressure of 100 PSI (7.03 kg/cm) and at temperatures of not over 250°F (120.9°C); in hydraulic and transmission systems ² to a maximum pressure of 450 PSI (31.64 kg/cm) and at temperatures of not over 270°F (132.1°C). After installation, the probe adapters can be left in the test locations for future test purposes. Always remove the probe and install the adapter plug after the tests are completed. Install the probe adapters in test locations as follows - 5P2720 Adapter, 1/8"-27 NPT threads; 5P2725 Adapter, 1/4"-18NPT threads; 5P3591 Adapter, 9/16"-18 threads.

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Using the probe seal at pressures and temperatures higher than those indicated above can result in injury to personnel or damage to the machine.

Installation Of 5P2720, 5P2725 And 5P3591 Probe Adapters

(1) Clean the area around the test location pipe plug and remove the pipe plug.

(2) Install the correct adapter (1) in the test location. Remove plug (2). Lubricate the probe with petroleum jelly and install the probe carefully through the hole in seal (3) and into the adapter. The hole in seal (3) is self-sealing. After the probe is installed seal (3) will seal around the probe. Do not exceed 30 lb. ft. (4.1) torque when tightening the probe.

NOTE: Use only the following probes with the probe adapter groups: 5P2717 Thermistor Probe, 1.00" (25.4), 9S9105 Thermistor Probe, 1.50" (38.1) or the 5P2718 Pressure Probe, .984" (25.0).

(3) Connect the probe lead to the probe and continue with the test procedure.

NOTE: After the test is completed and the test probe has been removed, always install plug (2) in the probe adapter. Plug (2) keeps dirt and other foreign material out of the probe adapter and prevents damage to seal (3). It also is a safety plug to prevent possible leakage when not being used for tests.

Preparing The Thermistor Thermometer For Use

IMPORTANT: WHENEVER THE INSTRUMENT IS TO BE USED, LAY OR HOLD IT IN A HORIZONTAL POSITION.

(1) Install three (Size AA, 1.4 volt) mercury batteries by removing eight screws (7) and lifting out the meter face panel.

(2) To test the probes, allow them to stabilize at room temperature for at least 5 minutes. Plug all four probes into the meter and compare the readings. If the readings vary, use an ohmmeter on each of the probes and compare the resistance values with the chart. If the probe resistances are equal and correspond to the values on the chart, check for defective connecting cable assemblies.

(3) To check the zero adjustment, rotate the selector knob to "OFF." The needle should be within one increment of the 32°F (0°C) mark. If adjustment is needed, refer to the Calibration Instructions on page 7. Note: If the instrument requires frequent zero adjustments, the instrument needs repair.

(4) Adjust the battery voltage. Rotate selector knob (8) to "V.ADJ." and align the needle with the mark on the meter face by turning slotted screw (9).

Using The Thermistor Thermometer

When analyzing the cooling system for overheating, make the simplest visual checks first:

1. Engine and Machine Cleanliness

2. Coolant Level

3. Radiator Core Condition (To test the radiator core, refer to Special Instruction Form SMHS7063).

4. Fan and Belt Condition

5. External and Internal Leaks

6. Inadequate System Pressure

Air temperatures, altitude, improper gear selection, and lengthy periods of operation near lug or converter stall conditions are also factors that must be considered.

(1) When using the Thermistor Thermometer to verify system temperatures, the probes can be installed in various locations. To detect any bad connections or cables, rotate the selector knob to all positions and observe the needle. If any circuit is open, the needle will move to a position less than 32°F (0°C). With a direct short in the circuit, the needle will move to a position in excess of 300°F (150°C).

(2) Proper probe and adapter selections are important in obtaining accurate temperature readings. Make sure the probe is installed a minimum of .05"-0.8" (12.7-20.3) into the liquid of the system being tested. The following is a list of system areas that can be tested, and the respective probe locations. The first four are basic areas to check in determining an overheating problem. Caution: The design of the probe ends does not permit excessive torque; therefore, do not exceed 30 lb. ft. (4.1) torque when tightening.

System Areas & Probe Installation

1. AMBIENT - Air temperature away from the machine and not in direct sunlight.

2. TOP TANK - When possible, pipe plug location in the radiator top tank. Otherwise, sensor bulb indicator location in the regulator housing or water manifolds.

3. BOTTOM TANK -Radiator drain outlet or pipe plug location i radiator lower elbow.

4. TORQUE CONVERTER - Sensor bulb indicator location in torque converter outlet.

5. TRANSMISSION - Lube valve tap, lube line tap or oil filter tap.

6. ENGINE LUBRICATION OIL - Engine block oil distribution gallery.

7. REGULATOR - Sensor bulb indicator location.

8. RETARDER - Sensor bulb indicator location.

9. HYDRAULIC OIL - Hydraulic tank, pump or line connecting the pump and the control valve. The probe can be installed in the lines leading from the control valve but the oil must be cycled until stabilized at system temperature to get an accurate reading.

10. TRUCK OIL DISC BRAKES (HYDRAULIC OIL) - Sensor bulb indicator location in hydraulic tank.

(3) Check the 5P1719 Meter to make sure it is on zero with the power off. Adjust the Thermistor Thermometer battery voltage prior to each using. Rotate selector knob (8) to "V. ADJ." and align needle with the mark on the meter face by turning slotted screw (9).

(4) Refer to the following chart which lists system areas to be compared, expected temperature readings, problems and probable causes of the problems. To obtain accurate readings, measure temperatures during actual working conditions.

NOTE: If the machine is being tested in a rainstorm or partially submerged in water, the electrical connectors will tend to short out. To prevent this, apply a liberal quantity of 4L7464 Silicone Grease to the electrical connectors before the cable is attached to the thermistor probe.

Calibration Instructions

The following conditions will make it necessary to calibrate the thermometer readout: Three to six months use of the Thermistor Thermometer; replacement of the 5P1719 Meter; Thermistor Thermometer has been dropped or otherwise damaged.

(1) To calibrate the Thermistor Thermometer read-out, turn selector knob (8) to "OFF". The needle should be within one increment of the 32°F (0°C) mark. Turn slotted screw (10) until the needle is properly aligned.

(2) Adjust the battery voltage. Rotate selector knob (8) to "V.ADJ." and align the needle with the mark on the meter face by turning slotted screw (9).

(3) Remove the panel from its case. Using a 1% tolerance resistor with a rating of 2000 ohms, rotate selector knob (8) to an input position and connect the resistor to the corresponding input jack as shown. The meter should read 213.5-214.5°F (100.7-101.3°C).

(4) If the temperature reading in step 3 is inaccurate, adjust potentiometer (11) to get the correct calibration. Use an additional 10.00K ± 1% resistor to check instrument linearity. This resistor should produce a reading of 123.5-129.5°F (50.8-54.1°C). If not, replace the 5P1719 Meter.

Troubleshooting The Electrical Components

This section is written as an aid for troubleshooting the Thermistor Thermometer for electronic technicians only. It must not be used by service personnel with no training or knowledge of electronics. A circuit board illustration is included showing the position of each of the components. Also included is a schematic of the electrical circuit so the technician can easily follow the sequence of the circuit.

Checking For Shorts In Battery Circuit

Remove the eight bolts and lift the panel out of the carrying case. Remove batteries (1). Check the batteries for corrosion or low voltage. Replace batteries as necessary. Check at locations (B) and (C) for broken or pinched wires. Check the battery solder tabs, at location (A), for a short against either the battery mounting bracket or the carrying case. Bend the tabs if necessary and cut-off any excess wire or solder that is on the tab. Install the meter face panel in the carrying case. Check for, and correct, any interference at assembly.

Removal And Replacement Of Components

Cut the connecting wires of the component and remove the component from the circuit board. Use a 25-75 watt soldering iron with a clean .12" (3,0) tinned tip and remove the remainder of the wires, one at a time. This can be done on the foil side of the board. Use either Dri-Wick and the iron or drill through the solder from the component side of the board with a fine drill.

IMPORTANT: Never install a used part; at all times, install new components.

Clean the solder with alcohol or trichlorethylene. Make a check of the circuit to be sure that it is in operating condition. Paint the areas where the varnish was removed.

IMPORTANT: Installation of components by methods other than the directions above can cause damage to the circuit board.

On the following schematic of the electrical circuit the rotary switch is shown in the OFF position with section (A) nearest to the panel. All sections are as seen from the front of the instrument. Only those switch contacts shown in black are used in this model. The contact numbers are in clockwise positions.

Schematic And Circuit Board Illustration

Parts Information

Write to Flo-Tech, Inc., 403 South Washington Boulevard, Mundelein, Illinois 60060, U.S.A., to get parts and parts prices for service replacement. Any orders for the following parts must be sent directly to them.

The description of the components is complete enough to get similar components locally. But, it is the recommendation of Flo-Tech, Inc., that the "Electronic Components" should be ordered directly from them. This recommendation is made because of the different quality of parts from manufacturer to manufacturer. Components from other sources will not necessarily be of the correct size to fit the circuit boards. Also, some components are not manufactured to the correct electrical tolerances and can prevent correct operation of the instruments. Many of the parts in the list are manufactured especially for these instruments and have no other application.

Service Parts

For repair, return well packaged and prepaid to:

Installing 5P1719 Replacement Meter For The 9S9102 Thermistor Thermometer

(1) When replacing the meter, it is necessary to reuse the original scale face. Carefully remove the white scale face from the old and new meters. Then press the original face on the new meter. Once the new meter is installed in the test instrument, it is necessary to recalibrate the meter [see page 7 for calibration instructions].

NOTE: A 2P2328 Cable Assembly, 65' (19.8 meters) in length, is available to reach from the rear engine to the operator's seat on twin engine tractor-scrapers.