C. With Ready-For-Starting 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).

C. With ready-for-starting lamp engine 615,616 in model 123.1

a) Preglow system not preglowing




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

Attention!
Preglow system is fused. Check fuse. (The separate fuse box is mounted on front wall of engine compartment).




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

If voltmeter indicates 12 volts, look for fault on glow plugs or their connections.

If voltmeter indicates 0 volt, look for fault on preglow starter switch or its connections.




1. Check glow plugs for interruption
Connect minus cable of voltmeter to ground. Check voltage with plus cable of voltmeter at current input and current output of the four glow plugs.

If 12 volts are measured at current input of a glow plug and 0 volt at output, this glow plug is interrupted and must be replaced.

2. Checking preglow starter switch and Connections
Connect minus cable of voltmeter to ground. Measure the following values with plus cable of voltmeter at connections of preglow starter switch:

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




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

Voltage in switch position I and II on terminal 19 and 50a approx. 11 volts.

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

b) Preglow system preglows too slow or too fast

Glow period at 52 amps:

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




This complaint is caused by insufficient current flowing through preglow system as the result of transfer resistances, or too much current as the result of a short-circuit.

Measure glow current first with ammeter.

For this purpose. connect ammeter to connection of glow plug for cylinder 4.

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

Measured after 15 seconds (battery charged at least 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-circuit in preglow system is indicated (glow plugs, preglow starter switchl.

If a glow plug is lost by a short-circuit, measure glow current once again after replacing plug.

c) Preglow system glows, but preglow indicator lamp not indicating

Connect voltmeter to connection LA of fuse box (3) and to ground. Actuate preglow svstem and read voltage on voltmeter.

If voltmeter indicates approx. 12 volts, check bulb and feed line of preglow indicator lamp (pav attention to tight seat of bulb in socket).





Pull coupler from thermo time switch and connect directly to ground. Actuate preglow system. If preglow indicator lamp lights up, replace thermo time switch.




If voltmeter indicates 0 volt, measure preglow current.

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

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

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