"Alan Petrillo" wrote:
> I have an old diesel truck with the C223 engine.
> I'm trying to figure out what the temperature sensors do.
> There are
> three of them on the thermostat housing. The one on the lower
> goes to the glow plug timer. Does anyone have any idea what
> the other
> two do? They are on the upper thermostat housing, and
> labelled 1 and 2.
> I assume one of them goes to the idiot light, but this truck
> have a temperature guage, so what does the other one do?
The temp sender that goes to your glow plug is a switch that prevents
the glow plugs form being activated when the engine is started when
the engine is already hot.
There should be another temperature sender located a bit further down
on the side of the thermostat housing to keep it low as possible. This
should be the sender for you gauge.
To test exactly what each one does you can simply pull the wire off
the sender and touch it somewhere on a place on the engine that has a
good earth. In the case of a gauge the needle should move right up to
the hot mark of the gauge. In the case of a light the temp light on
the dash should come on as though it was overheating. To test a light
you will probably need to have the engine running and to test the
gauge you will just need to have the ignition in the start position.
The glow plug sender can easily be tested when your engine is cold by
again earthing the wire for that sender and turn your ign to the start
position. While that wire is earthed the glow plugs should not come
Do not earth your gauge (temp sender)wire for any extended length of
time so that you do not damage your gauge. Just put it on for long
enough so that you can see that it works (10-15 seconds should be
okay) . Its a job best done by 2 people. Besides that there is
nothing else you can damage, because all the temp sender wires are
earth wires anyway. But with a gauge temp sender they are not just a
switch like the others that are either off or on. The temp sender
changes the resistance between the wire and the earth of your engine
and as the temp rises the resistance between the 2 becomes less. But
even at full temp it will still have a resistance of "X" amount and
your gauge is set to work within these boundrys. But when you earth
the wire there is no resistance at all creating a complete closed
circuit between the two and the gauge is not designed for this.
My C223 engine only ever had two temp senders, one for a temp gauge
and on for the glow plugs, so im not quite sure why ther would be 3.
Maybe your truck has a gauge and a light which would require 2
different types of senders, or maybe they might just have a back up
one just in case one of them fail, but I dought that.
Maybe you can find out by doing the test above.
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