Service Information And Instructions For Use of 5P8585 Leak Detector{0651, 7320} Caterpillar

The 5P8585 Leak Detector can find refrigerant leaks in air conditioners with R-11 or R-12 refrigerant gas, even if the leak is as small as one-half ounce of gas per year. The instructions that follow are for the correct operation, maintenance, troubleshooting and repair of present 5P8585 Leak Detectors as well as the previous model which does not have a power indicator lamp.

Features (Characteristics) Of The 5P8585 Leak Detector

SENSOR: For easy removal and installation, the ionization type sensor has a plug-type connection. The spring protector can also be removed.

CALIBRATION: An internal R-11 refrigerant reference leak source makes it possible to adjust the sensitivity of the leak detector.

DETECTOR ALARM: A bright light and an internal horn give an indication when a leak is found. (Horn on newer models only)

BATTERY INDICATOR: A green, light emitting diode shows when the unit is on, and shows the condition of the internal batteries. (Light on newer models only)

PROBE EXTENSION: A flexible, 457 (18.0") probe makes it possible to check areas where access is difficult.

STORAGE: A vinyl case gives protection during transport and storage of the detector.

Specifications Of The 5P8585 Leak Detector

SENSITIVITY: One-half ounce per year leakage rate of R-11 or R-12 refrigerant gas.

POWER: Needs two D-size alkaline batteries.

RESPONSE TIME: An alarm is heard approximately one second after a leak is found.

REFERENCE LEAK: A bottle of R-11 refrigerant gas has approximately one year life at one-half ounce per year leak rate. The bottle can then be filled again.

WARM-UP TIME: None is necessary.

OPERATION TEMPERATURE RANGE: 0°C (32°F) to 55°C (131°F).

WEIGHT: Approximately 0.51 kg. (1.12).

Operation Instructions For 5P8585 Leak Detector

Show/hide table

Always use protection goggles during service work on an air conditioner system.

(1) Carefully install sensor (1) into the end of connector (2). To install spring protector (3) over sensor (1), turn it in a counterclockwise direction on connector (2).

(2) Remove side cover (4) and put two D-size alkaline batteries in sleeve (5), with polarity as shown. Check reference leak bottle (6) for fluid and remove seal screw (7). Install side cover (4).

(3) Adjust the 5P8585 Leak Detector as follows: Turn thumbwheels (8) and (9) all the way to the left. Turn power switch (10) to ON. Newer models have a green power indicator light (11) which will come on to give an indication of the battery condition. When batteries are low, the light will become dim (low in light) and go out. Turn BAL thumbwheel (9) to the right until light (12) goes on, then turn thumbwheel (9) to the left until the light just goes out.

(4) Put the tip of sensor (2) in reference leak port (A). If light (12) comes on, the unit is adjusted. If light (12) does not come on, move the sensor away from leak port (A), turn BAT thumbwheel (8) a few teeth forward until light (12) goes on each time sensor (2) is put in leak port (A) and goes out when the tip is removed from port (A). Do not move the BAT thumbwheel forward more than necessary or the sensor's life will be decreased.

(5) During a check for leaks in an area of high concentration of refrigerant, the light may stay on constantly. If so, adjust the leak detector in the area of high concentration. After all large leaks have been stopped, make the adjustment to the unit in an area free of refrigerant, and the smaller leaks can be found.

(6) If the leak detector does not operate with new batteries and a full reference leak bottle, the sensor tip or spring protector need to be cleaned or a new tip installed. Remove the spring protector and use a soft camel hair brush or light breath to clean the sensor tip. Do not use compressed air or solvent. The spiral spring protector can be cleaned after removal from the sensor tip with detergent or solvent. During long storage periods or for shipment, remove the batteries from the unit to prevent damage from leakage.

(7) Parts available from Caterpillar for maintenance of the leak detector are:

5P9732 - Sensor and Spring Protector6V101 - Reference Leak Bottle5P8726 - R-11 Refill for Reference Leak Bottle

Principle Of Operation (See Schematic, Page 22)

(1) The refrigerant sensor tip has a filament with an output collector installed near it. When the filament is heated, a small current will flow to the output collector lead. The filament has a special cover material which causes the current flow to increase when it is in contact with a refrigerant gas. This increased current causes a voltage increase to a level detector. When the voltage goes beyond the point at which it was set, the level detector output activates the indicator light and horn through a transistor amplifier. Power supply for the circuits is from two 1.5 volt D-size alkaline batteries connected in series to make 3 volts. Since this voltage is not high enough to activate the level detector circuit, a switching type power supply is used to increase the voltage to positive (+) and negative (-) 9 volts.

Circuit Description (See Schematic, Page 22)

(1) Power from the two 1.5 volt batteries flows through switch S1 before it goes to the circuits. Power to the filament in the sensor tip flows from S1 to the battery control R10 which adjusts the current that flows through this circuit. A change in the filament current changes the detector sensitivity. Wires, in a location inside the flexible arm, make a connection from the sensor to the printed circuit board. The filament connections have an identification of E3 and E4 on the circuit board. The output signal on E2 flows through capacitor C1 to the level detector input. The negative 9 volt supply is connected to the sensor output lead through R8 and CR5. The filament is connected to the positive 9 volt supply line. This gives the voltage level across the sensor that is necessary for correct operation. Capacitor C8 is a filter for this voltage.

(2) The level detector uses an integrated circuit operational amplifier A1. It needs a +12 and -9 volt supply. A reference voltage, adjusted by the BAL (balance) control R9, is sent to the + input. When the voltage on the - input goes beyond this reference voltage, the output of A1 will go positive. Capacitors C6 and C7 are filters that remove transient noise pulses from the input signal, so they do not trigger (activate) the level detector. Resistors R1 and R3 hold the - input to an even voltage level when no input signal is present. R2 and R5 control the maximum range of BAL (balance) control adjustment.

(3) The PNP output transistors Q1 and Q2 are driven through R7 and zener diode CR1 by the level detector output. R6 holds Q2 off when no signal is present. Transistor Q2 gives base drive for Q1 in a darlington arrangement for increased power amplification. The output indicators, lamp L1 and horn H1, are driven by transistor Q1 when it is conducting (activated). When the horn and light come on, a large amount of current is taken from the batteries, which will cause their voltage to drop (decrease). This decreased voltage would cause the sensor filament current to decrease; to prevent a loss of sensitivity when the indicators are on, a voltage goes back to the sensor filament through resistor R12 every time Q1 is activated. This voltage is added to the filament voltage to keep the current at its original level.

(4) The positive and negative 9 volt power supply gets battery power through switch S1 and through resistor R11, that limits the current. This supply is a switching type power supply and uses Q3 as a 100 KHZ power oscillator. Q3 collector drives the transformer T1 primary with its 100 KHZ square wave signal. Capacitor C2 is in parallel with T1 primary to resonate at the oscillating frequency. Emitter drive for Q3 is given by a small primary winding on T1 connected in parallel with capacitor C3. The signal that comes from base to emitter of Q3 gives positive feedback, to cause oscillation to take place. R4 gives a DC bias voltage for Q3. The power supply output is given by a secondary winding on T1. It has more turns than the primary winding, and because of that, increases the output voltage to the necessary level. This AC voltage is rectified by diodes CR2 and CR3 and makes a DC voltage across C4 and C5. This voltage is limited to 18 volts by zener diode CR4. The center connection of the two capacitors is used as the common connection to give + and - 9 volt supplies. The + 9 volt output is connected directly to the battery negative lead. This puts the batteries in series with the + 9 volt supply to give + 12 volts with relation to common, as needed by A1.

(5) The power-on and battery condition indicator CR6 is connected across the batteries after S1. The maximum light output of the light emitting diode CR6 is limited by R13. Earlier models of the leak detector do not have the battery indicator lamp, or the horn.

Troubleshooting And Repair

This section is written as an aid for electronic technicians only, in troubleshooting the circuits of the leak detector.

(1) Make all the necessary maintenance and general checks of the leak detector. If the unit still does not operate, remove the cover and inspect for defects that can be found visually, such as loose solder connections, broken wires and burned components. If the location of the problem cannot be found this way, the voltage and wave forms must be checked to find the location of the problem in the circuit. Component identification marks on the printed circuit board are the same as shown on the wiring diagram.

Use Of Voltmeter For Circuit Voltage Checks

The conditions for the voltage test are:

1) All voltage measurements are nominal.

2) Voltmeter input is 20,000 OHM/Volt or higher unless otherwise given.

3) Battery voltage is 2.8 volts.

4) Sensor is not installed.

5) All voltages are with respect to circuit common (counterclockwise terminal on R9) as shown on the schematic diagram.

6) Balance control (R9) and battery control (R10) positions are as shown if their position (adjustment) changes the value.

(1) Power supply voltages.

(2) A1 level detector voltages.

(3) Transistor voltages.

(4) Sensor voltages.

NOTE: These measurements (*) are with voltmeter that has input of at least 20 MEG-OHM. A voltmeter with lower input resistance will cause the voltage measurement at these points to be lower.

Use Of Oscilloscope For Troubleshooting The Power Supply

The conditions for the test are as follows:

1) Oscilloscope input is 1MEG-OHM minimum.

2) Battery voltage is 2.8 volts.

3) Sensor tip is not installed.

4) All wave forms are with respect to circuit common (counterclockwise terminal on R9) as shown on the schematic diagram.

5) Horizontal sweep at 2 miscoseconds/DIV.

6) Vertical sensitivity as given.

(1) TP-1 Collector of Q3 (T1 Lead No. 9) Vertical sensitivity: 5 volts/DIV. Bottom trace is zero volts.

(2) TP-2 Emitter of Q3 (T1 Lead No. 11) Vertical sensitivity: 5V/DIV. Bottom trace is zero volts

(3) TP-3 Base of Q3 Vertical sensitivity: 2V/DIV. Bottom trace is zero volts

(4) TP-4 Transformer output (T1 Lead No. 13) Vertical sensitivity: 5V/DIV. Dark grid line in center of trace is zero volts

Parts List

NOTE: Kit J26933-6 is available and has LED, all resistors, capacitors, and lamps. Order from KENT-MOORE.

Wiring Diagram And Test Points

Parts available from CATERPILLAR for maintenance of the leak detector are:

5P9732 - Sensor and Spring Protector6V101 - Reference Leak Bottle5P8726 - R-11 Refill for Reference Leak Bottle

Parts for maintenance and repair are available from: