B. With Preglow Indicator Lamp (Model 123.1)

Checking Preglow System

Conventional tools
Voltmeter (measuring range 0-3 volts/0-16 volts)
Ammeter (measuring range 0-60 amps)

Note
Battery charged mm 60 % (acid density approx. 1.22 g/cc).

B. With preglow indicator lamp engine 615,616 in model 123.1

a) Preg low system not preglowing




This complaint is based on an interruption in current circuit of preglow system.

Attention!
The preglow system is fused, check fuse. (The separate fuse box is mounted on front wall inside engine compartment).




Adjust voltmeter, measuring range 0-16 volts. Connect plus cable of voltmeter to input (threaded stud) of glow plug of 4th cylinder and minus cable of voltmeter to ground Actuate preglow system and read voltage on voltmeter.

If voltmeter indicates 12 volts, the interruption is at glow plugs or their connections.

If voltmeter indicates 0 volt, the interruption is at preglow starter switch or its connections.




1. Checking glow plugs for interruption
Connect minus cable of voltmeter to ground. Check voltage at current input and output of the four glow plugs by means of plus cable. If 12 volts are measured at input of a glow plug and 0 volt at output, the respective glow plug is interrupted and must be replaced.




2. Checking preglow starter switch and connections
Connect minus cable of voltmeter to ground. The following values must be measured at connections of preglow starter switch with plus cable of voltmeter:

In switch position 0 (key in steering lock in position "2") on terminal 15/54 = 12 volts.

In switch position I and II (preglow or start position) on terminal 19 and 50a = approx. 11 volts.

If the voltage at terminal 15/54 = 0 volt, check line to steering lock switch or steering lock switch itself, as well as the respective connection.

If the voltage at terminal 19 and 50a = 0 volt, replace preglow starter switch.

b) Preglow system preglowing too slowly or too fast

Glow period at 52 amps:

Nominal time at: +20 °C approx. 12 seconds
- 5 °C approx. 30 seconds




In the event of this complaint, the current flowing through preglow system is too low as a result of transfer resistances, or too high as a result of a short~ircuit.

First, measure glow current with ammeter.

For this purpose, connect ammeter at glow plug connection of cylinder 4.

Glow current in preglow position: approx. 50-55 amps.

Measured after 15 seconds (battery charged mm 60 %).

If this glow current is not attained, measure voltage drop in preglow system with voltmeter.

Check connections for tight seat.




If this glow current is exceeded, a short~ircuit in preglow system is indicated (glow plugs, preglow starter switch).

If a glow plug is lost as the result of a short~ircuit, exchange plug and measure glow current once again.

c) Preglow system glows, but preg low indicator lamp not indicating




Connect voltmeter to connection LA of fuse box (5) and to ground. Actuate preglow system and read voltage on voltmeter.

If voltage indicates approx. 12 volts, check bulb and feed lines of preglow indicator lamp (pay attention to tight seat of bulb in socket).

If voltmeter indicates 0 volt, measure preglow current.

If approx. 50-55 amps are measured, the reed contact of the fuse box is defective and the fuse box must be replaced.

If a low glow current is measured. a transfer resistance in preglow system is indicated or the battery is insufficiently charged.

Check connections of glow plugs for tight seat and recharge battery, if required.