Cessna 170, Service Manual

Page 1: ...The Cessna 170 Service Manual Published by The International Cessna 170 Association ELECTRICAL SYSTEM 2004 The International Cessna 170 Association and George Horn All Rights Reserved ...

Page 2: ...d a complete manual and helped influence the final products outcome Wherever possible part numbers have been included in the text for convenience s sake Be aware that part numbers may be superceded at some point in time and be certain to confirm any part requirements An attempt has been made to help the owner with unsophisticated repair and troubleshooting techniques Some of those activities may n...

Page 3: ...Cessna 170 Service Manual Electrical System ELECTRICAL ...

Page 4: ...or Tests Repairs and Adjustments Simple Generator Test Page 8 Generator Short Test Voltage Regulator Repair and Adjustment High RPM Gen OnLine Speed Adjustment of Voltage Adjustment of Current Isolating Too Low High Charge Page 9 Inspecting Regulator Regulator Point Cleaning Engine Starter Page 10 Starter Electrical Circuit Starter Lever Cable Adjustment AIRCRAFT LIGHTING SYSTEM Landing and Taxi L...

Page 5: ...cs Electrical Schematics SNs 20267 THRU 26372 SNs 25373 THRU 26995 SNs 26996 and ON SNs 26996 and On Inst Pnl Electrical Wiring Diagram Identification Wire ID Length Sizes Appendix EL Illustrations Ground Service Plug and Early Battery Solenoid Relay EL 1 Late Style Battery Solenoid Relay Battery Solenoid Relay and Master Switch Circuit EL 2 Landing Light Adjustment MultiMeter EL 3 Test Leads Gene...

Page 6: ...original solenoid was contained within a metal box while subsequent models resemble a metal cylinder with two large threaded terminals for main battery cable connections one from positive battery terminal the second connected to the rest of the aircraft electrical system at the starter switch mounted upon the starter motor and either one or two smaller terminals One of these smaller terminals is u...

Page 7: ... POWER TO BUS BUT WILL NOT CRANK ENGINE Low Battery Check specific gravity Charge battery Faulty battery cables Inspect for corrosion and poor connection Repair wiring Clean and reconnect Battery cell shorting under load This cause is very difficult to detect Even a good battery connected to a shorted battery will behave similarly Only when a shorted battery is completely removed from the system w...

Page 8: ...ttery Manufacturers TESTING THE BATTERY The specific gravity of the battery may be measured with a hydrometer to determine the state of battery charge If the hydro meter reading is low slow charge the battery and retest Hydrometer readings of the electrolyte must be compensated for the temperature of the electrolyte Some hydrometers have a built in thermometer and conversion chart The following ch...

Page 9: ...be free from the bracket d To install a ground service receptacle reverse this procedure Be sure to place the ground strap on the negative stud GENERATOR POWER SYSTEM The generator power system consists of the generator voltage regulator and master switch The generator output is controlled by the voltage regulator to compensate for the amount of electrical power being consumed and the condition of...

Page 10: ...ime the generator be replaced that a new oil seal PN 352068 be installed on the front of the generator Remember that the oil seal open end faces TOWARD the engine to keep oil inside the engine Examine the generator drive shaft to detect interference between the woodruff key and the oil seal Any interference will damage the oil seal with resultant loss of engine oil Generators are usually received ...

Page 11: ...y circuit when the generator is rotating so slowly low engine RPM that it cannot produce useful electricity This prevents the Battery from discharging into the generator circuits The Cut Out Relay may be identified as it is directly connected to the system via the BATtery terminal on the regulator The Current Regulator Relay controls the amperage output of the generator by connecting directly to t...

Page 12: ...there is STILL NO CHARGE then connect a small test jumper wire between the ARMature and BATtery terminals of the voltage regulator as illustrated in Appdx EL Fig EL 09 TEST 3 Cut Out Relay This shorts out the Reverse Current Relay and the Current Regulating Relay and connects the regulator directly to the battery Run the engine again at approx 2 000 RPM and if a charge now occurs the voltage regul...

Page 13: ...than fully charged A voltage meter reading of approximately 11 5 volts is ideal Use a short test jumper lead as in Appdx EL Fig EL 09 TEST 3 Cut Out Relay and from engine idle slowly increase engine speed until the first indication of a charge occurs If this speed is appreciably below the previously observed ON LINE speed then adjustment of the Cut Out Relay spring tension to a lower tension value...

Page 14: ...rebuilding is usually not warranted But sometimes regulators can be returned to service with minor repairs covered under these inspection procedures After removing the regulator from the aircraft remove the regulator cover and inspect for any obvious indication such as burned components burned paint or smell corroded contacts or broken solder joints Examine the underneath side of the regulator for...

Page 15: ...enoid The other is a 10 or 8 gauge wire that brings electrical power directly to the cockpit main electrical buss It is merely using the starter switch terminal as a source of electrical power since that terminal is energized whenever the battery solenoid is activated by the cockpit master switch STARTER LEVER AND BOWDEN CABLE ADJUSTMENT The starting lever should have a minimum amount of free play...

Page 16: ...OME LIGHT Several types of instrument light have been utilized in Cessna 170 aircraft Early instrument panels incorporated individual indirect lighting within the floating instrument panel Some later models were equipped with dual ultra violet fluorescent lamps however most models utilized plain incandescent lamps within an overhead console either mounted within dedicated sockets and directed thro...

Page 17: ... it from the main body exposing the ceramic heating unit surrounding the inner pitot tube Remove the local inspection cover and disconnect the wiring terminals from the harness Slide the heater unit from the pitot tube Installation of the replacement unit is the reverse procedure The stall warning lift detector heating unit is removed by first removing the lift detector from the leading edge of th...

Page 18: ...With the Master switch OFF Use the continuity mode function of your MultiMeter across the input side and exit side of the fuse holder or C B to confirm continuity across the unit If no continuity then repair replace the current limiter Caution Do not accidentally allow voltage to flow through the MultiMeter in the continuity mode or the meter will be damaged This is why we checked it with the Mast...

Page 19: ... exist It is not recommended for use in communication or navigation systems Note Aluminum and Silver coated wire was never used in Cessna 170s originally but this information is being supplied in the event any is found subsequently installed SILVER COATED WIRE is sometimes found and used where temperatures do not exceed 392 F 200 C CAUTION An inflammability hazard exists when silver or silver plat...

Page 20: ... enlarged Many types of aircraft splice connectors are available for use when splicing individual wires Use of the self insulated splice connector is preferred however a noninsulated splice connector may be used provided the splice is covered with plastic sleaving or heat shrink which is secured at both ends Solder splices may be used however they are particularly brittle and not recommended a The...

Page 21: ...ng cables having soft plastic insulation such as polyethylene because these materials are subject to deterioration and deformation at elevated temperatures Many coaxial cables have this type of insulation PROTECTION AGAINST CHAFING Protect wire and wire groups against chafing or abrasion as damaged insulation may result in short circuits malfunctions or inoperative equipment Support wire bundles u...

Page 22: ...er that matches the diameter of the stud Tightening terminal connections shall not deform the terminal lugs of the studs Terminal lugs shall be so positioned that bending of the terminal lug is not required to remove the fastening screw or nut and movement of the terminal lugs will tend to tighten the connection e Copper terminal lugs Solderless crimp style copper wire terminal lugs shall be used ...

Page 23: ...s measuring 9 32 X 1 1 4 AGS is a size no longer used by manufacturers and sometimes difficult to find therefore many owners substitute AGC fuses in similar amperages The AGC series is not an exact fit due to diameter and their performance is sometimes intermittent due to reduced contact area within the holder The original Cessna part number 0411023 is the AGS series fuse with a following dash num...

Page 24: ...lly cautious when replacing equipment and wiring in the aircraft Original wiring gauges switches and current limiters may not be adequate for subsequently added equipment Example An aircraft originally equipped with a 12 ampere generator was equipped with a 10 gauge wire in the main electrical supply buss circuits and in the generator to battery circuit If the aircraft was subsequently modified wi...

Page 25: ...Cessna 170 Service Manual Electrical System ELECTRICAL SCHEMATIC SNs 20267 THRU 25372 ...

Page 26: ...Cessna 170 Service Manual Electrical System ELECTRICAL SCHEMATIC SNs 25373 THRU 26995 ...

Page 27: ...Cessna 170 Service Manual Electrical System ELECTRICAL SCHEMATIC SNs 26996 AND ON ...

Page 28: ...Cessna 170 Service Manual Electrical System INSTRUMENT PANEL ELECTRICAL SCHEMATIC SNs 26996 AND ON ...

Page 29: ...Cessna 170 Manual Electrical System ...

Page 30: ...Cessna 170 Manual Electrical System ...

Page 31: ...Cessna 170 Manual Electrical System ...

Page 32: ...Cessna 170 Manual Electrical System ...

Page 33: ...Cessna 170 Service Manual Electrical System ...

Page 34: ...Cessna 170 Service Manual Electrical System ...

Page 35: ...Cessna 170 Service Manual Electrical System Appdx EL 1 Fig EL 01 Ground Service Plug and Early Battery Solenoid Relay Fig EL 02 Late Style Battery Solenoid Relay ...

Page 36: ...stem Appdx EL 2 Fig EL 03 Battery Solenoid Relay and Master Switch Circuit Fig EL 04 Landing Light Adjustment Land Lamp Taxi Lamp Position 1 56 Position 2 62 Position 5 56 Position 6 90 Position 3 62 Position 4 68 Position 7 50 Position 8 84 ...

Page 37: ...Cessna 170 Service Manual Electrical System Appdx EL 3 Fig EL 05 MultiMeter Fig EL 06 Test Leads ...

Page 38: ...Service Manual Electrical System Appdx EL 4 Fig EL 07 GENERATOR MOTOR TEST SCHEMATIC NEGATIVE BATTERY CABLE TO CASE POSITIVE BATTERY CABLE TO ARM TERMINAL FIELD TERMINAL TO CASE FIG EL 08 TEST FOR GENERATOR SHORT ...

Page 39: ...Cessna 170 Service Manual Electrical System Appdx EL 5 FIG EL 09 VOLTAGE REGULATOR CIRCUIT BREAKER OR REVERSE CURRENT RELAY ...

Page 40: ...Cessna 170 Service Manual Electrical System Appdx EL 6 TEST 1 CONFIRM REGULATOR GROUND TEST 2 ISOLATE REGULATOR ...

Page 41: ...Cessna 170 Service Manual Electrical System Appdx EL 7 Fig EL 09 cont d VOLTAGE REGULATOR TEST 3 CUT OUT RELAY Fig EL 10 STARTER CABLE LEVER ADJUSTMENT ...

Page 42: ......