A. With Glow Plug Resistance Control (Model 115.1)

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).

A. With glow plug resistance control engine 615,616 in model 115.1

a) Preglow system not preglowing

This complaint indicates an interruption in circuit of preglow system.




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

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

If the voltmeter indicates 0 volt, look for interruption at preglow starter switch or on glow plug resistance control.




1. Checking glow plugs for interruption
Connect minus cable of voltmeter to ground. Check voltage at current input and output of the 4 glow plugs by means of plus cable of voltmeter.

If a glow plug at current input shows 12 volts and at output 0 volt, the respective glow plug is interrupted and must be exchanged.




2. Checking preglow starter switch and glow plug resistance control
Connect minus cable of voltmeter to ground. By means of the voltmeter plus cable the connections of the preglow starter switch should indicate the following values:

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

In switch position I (preglow position) on terminal 19=approx. 11 volts.

Preglow starter switch

In switch position II (starting position) on terminal 17 and on terminal 50a = approx. 11 volts.

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

If the voltage on terminal 19, 17 or 50a = 0, exchange preglow starter switch.




Glow plug resistance control
Voltage at glow plug resistance control input and output approx. 11 volts.

If voltage is 0 the line or the glow plug resistance control is interrupted and line or control must be replaced.

b) Preglow system glows too slowly or too fast




In the event of such a complaint, the current flowing through the preg low system is too low as a result of transfer resistances or too high as a result of a short-circuit.

First measure glow current with ammeter.

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

Glow current in preglow position: approx. 50-55 amps.
Measured after 15 seconds (battery charged min 60 %).

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

Check connections for tight seat.




If this glow current is exceeded, a short-circuit in preglow svstem is indicated (glow plugs, preglow starter switch, preglow resistance control).

If a glow plug fails as a result of a short-circuit, measure glow current once again after replacing glow plug.