| ELECTRICAL SECTION (SWITCH GEAR AND INSTRUMENTS) SWITCH GEAR AND INSTRUMENTS Ammeter Readings The ammeter indicates the amount of current passing into or out of the battery. Supposing that the dynamo is generating 7 amperes and that some of the side and tail lamps are in use, taking, together with the ignition coil, 3 amperes, then 4 amperes are left for charging the battery. This is the reading given on the ammeter. With compensated voltage control equipment it must be remembered when noting ammeter readings that normally during daytime running, when the battery is in good condition, the dynamo gives only a trickle charge so that the charge, reading will seldom be more than 3 or 4 amperes.A discharge reading may lie given immediately after switching on the headlamps. This usually happens after a long run when the voltage of the battery is high. After a short time the battery voltage will fall and the regulator will respond, causing the dynamo output to balance the load.When starting from cold the charging current will.rise until it reaches a steady maximum at a speed of, say, 20 miles per hour, after which it will remain fairly high for about 10 minutes, then fall to a steady charge which is most suitable for the particular condition of the battery. Checking Ammeter Readings To check the accuracy of the ammeter readings, connect an ammeter in series with it and compare the readings of the two instruments.It must lie remembered that the ammeters used on motor vehicles are not precision instruments, as they are designed to withstand the excessive vibration that is possible under had road conditions. These instruments are, however, sufficiently accurate for checking the normal operation of the equipment. Ammeter Fails to Indicate Usually caused by the ammeter being overloaded due to a short circuit in the wiring between the ammeter and the cut-out and fuse unit. Examine the wiring for evidence of damage and fit replacement ammeter. In the event of an open circuit in the ammeter indicated by the lamps and accessories not operating when switched on, the ammeter can be "shorted" by joining its two terminals by means of a length of wire until a replacement can he fitted. Switch Units Occasionally, say when the vehicle is taken down for a general overhaul, the terminals of the switch should be examined and, if necessary, tightened. Remove any stray strands of wire which may cause a short circuit. Switchboard. (C.A.V. Type No. 47) This switchboard being only 3.5” (89 mm.) face-plate diameter, is a compact unit for flush fitting into a dashboard or panel. If sufficient slack is allowed in the cables the complete board can he withdrawn from the front of the dashboard by removing the clamp and the two nuts securing it in position at the back. The board is fitted with a main rotarv switch for the control of the tail, side and tail, head side and tail lamps, together will an additional turn switch fur ignition control. Either magneto or coil may be used, but it is not suitable for dual ignition. Dynamo charging is indicatcd by a red pilot light fitted to the right of the ignition switch. ELECTRICAL SECTION (SWITCH GEAR AND INSTRUMENTS) To Dismantle the Board for Cleaning or Replacing Contacts The complete board should be removed from its faceplate or dash panel and all cables disconnected. (a) Remove fixing screw "D" and main switch handle "E." (b) Remove fixing screw "F" and ignition knob "G." (c) Remove fixing nuts "H" and clamp "J." (d) Remove fixing nuts, spring washers and plain washers " K." (e) The terminal base can now be removed from the body. Take care that the ignition switch parts are not lost, as they will be liable to fall out when the body is removed. (f) Examine ignition switch contact pins and locating sockets "L." Clean with very fine carborundum paper it they are in a dirty condition. Examine the fixed main contacts "N." They can be easily removed by unscrewing the one screw "O." If dirty, clean as above, take care not to bend them out of shape and make sure they make good contact when replaced. If badly burnt, bent or pitted, replace. (g) The main rotor contact can be cleaned by first extracting the two screws "P" from the back. This will allow the removal of the bracket "Q" from the rotor "R." Take care not to lose the locating steel ball "S." Clean the contacts if necessary, but replace if badly burnt or corroded. See that the screws "T" holding the springs are perfectly tight. (h) If the brass pillars "U" holding the contacts have become loose, tighten by means of the countersunk screw located in the respective terminal on the back of the base and accessible after removing cable screw. (i) Examine the lamp holder plunger "V," clean the tip if dirty ; a few drops of oil in the socket "W" will ease any stiffness, but keep it away from the plunger tip. See that the small pressure prongs in the side lamp holder " X" have not been bent out of place so that the locating pressure on the lamp is lost. Re-assembling the Board Smear the rotor bearing pin with vaseline and locate the rotor in the metal base bush so that the square is parallel with both the horizontal and vertical axis of the switchboard when it is in the normal mounting position and the small contact is across the two fixing spring contacts, i.e. when the switch is in the maximum "on" position. After coating the steel ball with vaseline, place it in the locating hole in the stop plate, that is, on the horizontal centre line. Place the bracket "Q" over the rotor so that the small hole locates over the steel ball; fix from the back with two screws "P." Locate the ignition switch contact piece "Z" so tliat tlie contact pips bridge across the C+ and B+ sockets, i.e. in an almost vertical position. Place the spiral spring "AA" over the square portion of the moulded ignition rotor and locate it in the square of the contact piece "Z" so that the flats of the brass hexagon on top of the rotor are parallel with the vertical centre line of the switchboard and the cut-away portion of the moulding points towards the main switch spindle.Replace the body and switch handles in the reverse order of the dismantling instructions a, b, c and d.If the small insulating sleeves "AC" become loose they should be replaced and held in position with fish glue.On boards fitted with the flat type clamp, always replace the insulator "AB" before the clamp. |
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| SWITCH BOX REPAIR SECTION FROM MORRIS COMMERCIAL SEP. 1940 SERVICE MANUAL |