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Many Standard 23C diesel engines have the ‘Thermostart’ heating and vaporising coil fitted in the inlet manifold.  Effective as this is, FE-35 tractors sold for use in areas of the world where extreme cold temperatures are expected were often fitted with ‘cold climate heads’ that have individual heater plugs for each pre-combustion chamber.  Tractors equiped with this system do not have the thermostart system fitted.


Heater plugs fitted to massey ferguson 35 4 cylinder head to aid starting


It is still possible to get the glow plugs (or alternatives) from some suppliers, but they are becoming more difficult to source in some contries.  We are going to take a look at the system, the components, the wiring diagrams and an alternative system built from more easily obtainable components that offers some advantages to the original system.

We’ve got some really helpful photos and diagrams to show you exactly what to do if you need to work on the heater system.


Per owns a cold climate FE-35 over in Canada, and he’s written a comprehensive article about the system on his tractor and how he has converted it.  The following information summarises Per’s article, but to read the full article then we would recommend taking a look at Per’s page on the subject (and there’s lots more great stuff on his website too!).

If you are able to source the original type of glow plug and ballast resistor (or manufacture one) then you would have no need to change, but this information may be useful for those of you who cannot source the original equipment.


The Glow Plugs

The heater plugs as specified in the MF manual are…

KLG. Z 161/3  (1.7V. 38 amps)

superseded by…

Lodge D.T. 14 L-1.7V  (1.7V. 38 amps)

KLG. GF. 205.T  (1.7V. 38 amps)

The two plugs on the left and centre of the picture below are what was removed from Per’s tractor.  The plug in the right of the picture is the new replacement plug that also fits these engines (and comes from a Land Rover engine).  However, the new plugs are 12V, so it would be necessary to convert to a parallel wiring system if you use to this type of plug.

The old plugs are easily identifiable by the insulating washer (even when fitted to the engine).


The Originals, And Replacement Plug

glowplugs for Standard 23C diesel engine

Original Wiring Diagram

Wiring diagram for glow plugs


New Wiring Diagram

Alternative wiring diagram for MF35



Wiring the new glow plugs in parallel also gives us an advantage.  Using the old series wiring system means that if one plug fails, then none of the others would work either.  Parallel wiring means that if one plug were to fail then the other three would still be receiving current and hence working.

The other train of thought on this is that if a plug blows when in series you will know something has gone wrong and you will replace the faulty plug (there is a warning lamp on the original system to indicate this – if it doesn’t light).  The potential disadvantage of parallel wiring is that you don’t realise when one plug blows, then some time later the next plug may blow.  The operator may then think that starting performance is slowly deteriorating and may not realise it is the plugs.

It is also possible when the corkscrew / coil type of glow plugs burn out, that the element can drop into the pre combustion chamber and get into the cylinder itself.  The probe type of plugs are much less likely to suffer from bits falling off.

The Ballast Resistor


Ballast resistor for MF35 heater plug circuit

Newly manufactured ballast resistor.

The ballast resistor was originally fitted to prevent over-loading during the initial heating period.

The ballast resistor is not necessary with the new plugs wired in parallel, as each plug is 12 volts.

The ballast resistor in the photograph above was manufactured for Per by one of his friends.  His friend used 14 gauge Nichrome wire and made four new fibre washer insulators.

We’ve also found that Land Rover parts suppliers stock balast resistors (link to balast resistor part).  We haven’t checked to see if this component is the exact same physical size, so you would need to do your homework on this one.