Using 8T470 Thermistor Thermometer Group{0776} Caterpillar


Using 8T470 Thermistor Thermometer Group{0776}

Usage:

All Caterpillar Machines

The 8T470 Thermistor Thermometer is used to analyze overheating problems; and it is capable of reading the temperature of transmission and engine lubricant, and fluids in engine cooling systems and hydraulic systems.

Components Of 8T470 Thermistor Thermometer Group


1. 6V6045 Case SEHS8009 Decal

2. 8T465 Thermometer 6V3080 Base

3. 6V3072 Case SEES5661 Decal

4. 6V6105 Block

5. 8B1931 Bushing

6. 4M5317 Bushing (4)

7. 20639 Adapter (4)

8. 9S9106 Angle Adapter (2)

9. 3B7721 Bushing

10. 3S8684 Fitting

11. 9S9103 Probe

12. 9S9104 Probe (2)

13. 9S9105 Probe

14. 5P2717 Probe

15. 5P2372 Cable (4)

16. 6V4034 Packing

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

NOTE: The Centrigrade portion of temperature scale for 8T465 Thermistor is in yellow.

Using 5P2720, 5P2725 Or 5P3591 Probe Adapters

The 5P2720 Probe Adapter (1) [1/8"-27 NPT thread], 5P2725 Probe Adapter (2) [1/4"-18 NPT thread] and 5P3591 Probe Adapter (3) [9/16"-18 standard thread] are for use with the test probes in the 8T470 Thermistor Thermometer Group. The 9F2247 Plug (4) is used as a protective cover for the inner seal of the adapter when the adapter is not in use. Remove plug (4) before installation of a test probe; always install the plug after a test has been completed.

The probe adapters can be used as follows: In fuel and cooling systems to a maximum pressure of 690 kPa (100 psi) and at temperatures of not more than 120° C (250° F); in hydraulic and transmission systems to a maximum pressure of 3100 kPa (450 psi) at temperatures of not more than 132° C (270° F).

------ WARNING! ------

Use of a probe adapter at pressures or temperatures higher than those indicated above can result in injury to personnel or damage to the machine.

-------WARNING!-------

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

(1) Clean the area around the test plug location, then remove the plug.

(2) Install the correct adapter (1) in the test location. Remove protective plug (2). LUBRICATE THE PROBE WITH PETROLEUM JELLY, then carefully install the probe through the self-sealing hole in seal (3) and into the adapter. After the probe has been installed, tighten the probe to a maximum torque of 40 N·m (30 lb - ft).

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

NOTE: After the test has been completed and the test probe 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). The plug also prevents possible leakage when not being used for tests.

Preparing The Thermistor Thermometer For Use

IMPORTANT: Always use the thermistor thermometer in a horizontal position.

(1) Install three (size AA, 1.4 Volt) mercury batteries by removing six screws (1) 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, turn the selector knob to "OFF". The needle should be within one increment of the 0° C (32° F) mark. If adjustment is needed, refer to the Calibration Instructions on page 10. NOTE: If the instrument needs frequent zero adjustment, it probably needs repair.


NOTICE

In an extremely dry environment, a static charge may build up on the meter face; this charge will cause an incorrect needle reading. To detect this condition, touch the meter face on either side of the needle; if the needle changes its position, discharge the meter face by wiping it with a damp cloth.


(4) Adjust the battery voltage. Turn selector knob (2) to "V. ADJ." and align the needle with the mark on the meter face by turning slotted screw (3).

Using The Thermistor Thermometer

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

(2) 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 0°C (32°F). With a direct short in the circuit, the needle will move to a position in excess of 150°C (300°F).

(3) Proper probe and adapter selections are important in obtaining accurate temperature readings. Make sure the probe is installed a minimum of 12.7-20.3 mm (.5"-.8") into the liquid of the system being tested. The following is a list of system areas to check in determining an overheating problem.


NOTICE

The design of the probe ends does not permit excessive torque; do not exceed 40 N·m (30 lb - ft) torque when tightening.


(4) Check the 5P1719 Meter to make sure it is on zero with the power off. Adjust the thermistor thermometer battery voltage before each use. Turn selector knob (1) to "V. ADJ." and align needle with the mark on the meter face by turning slotted screw (2).

(5) Refer to the following chart that 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 rain-storm or partially submerged in water, the electrical connectors will tend to short out. To prevent this, apply a liberal quantity of 5N5561 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 (1) to "OFF". The needle should be within one increment of the 0°C (32°F) mark. Turn slotted screw (2) until the needle is aligned with this mark.

(2) Adjust the battery voltage. Turn selector knob (1) to "V. ADJ." and align the needle with the mark on the meter face by turning slotted screw (3).

(3) Remove the panel from its case. Using a 1% tolerance resistor with a rating of 2000 ohms, turn selector knob (1) to an input position and connect the resistor to the corresponding input jack as shown. The meter should read 101°C (214°F).

(4) If the temperature reading in Step 3 is not accurate, adjust potentiometer R6 (4) to get the correct calibration. Use an additional 10.00 K ohm ± 1% resistor to check instrument linearity. This resistor should produce a reading of 51-54°C (124-130°F); if not, replace the 5P1719 Meter.

Troubleshooting The Electrical Components

This section is written as an aid for electronic technicians to troubleshoot the thermistor thermometer. 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

(1) Remove six screws 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.

(B) Removal And Replacement Of Components

(1) 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 3.0 mm (.12") 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.


NOTICE

Too much heat causes separation of the foil. Remove the remainder of the varnish from the foil with a knife. Install the new part with 0.8 mm (.03") rosin core solder of 60/40 or 63/37 alloy. Do not use acid core solder.


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

(2) Clean the solder with isopropyl alcohol. Make a check of the circuit to be sure that it is in operating condition. Put PC-101 Protective Coating (see Parts Information on page 13) on 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.

(3) On the following schematic of the electrical circuit, the rotary switch is shown in the OFF position with section (C) nearest to the front of 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 difference in parts quality from one manufacturer to another. 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 required 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.

For repair, return well packaged and, prepaid to:

Flo-Tech, Inc.
403 South Washington Blvd.
Mundelein, Illinois 60060 U.S.A.
Telephone (312) 566-9120
Telex: 270095

Order PC-101 Protective Coating from:

Steven-Daniels Corp.
2648 Freewood
Dallas, Texas 75220 U.S.A.
Telephone (214) 350-3555

Installing 5P1719 Replacement Meter For The 8T465 Thermistor Thermometer

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 10 for calibration instructions].

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