C223 temperature sensors

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 housing
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 doesn't have a temperature guage, so what does the other one do?
AP
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"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 > housing > 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 > doesn't > have a temperature guage, so what does the other one do? > > > AP
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 on.
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) . It’s 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 i’m 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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bigant916 wrote:

OK, but which one is it? Number 1 or 2 on top?

This truck doesn't have a guage, so maybe the one on the lower housing is the one for the idiot light?

That would work if the truck had a guage.

Maybe. I'll give it a look next chance I have, which will be monday.

Actually, in this model the glow plugs come on at every start, just the temperature switch changes the timing. I know it works, because I can hear the different relays click when the timing changes. It's just a matter of figuring out which sensor it is.

My Trooper does have both a guage and a light, and its C223-T has the same 3 sensors. The guage would require a sensor and the light would require a switch, so having two would make sense, but which one is which?

Indeed. Time to do some tinkering.
Thanks again, AP
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Alan Petrillo wrote:

What kind of truck are you talking about? As far as I know every car with a C223 engine does have a temp. gauge. Is it removed ???? Kind regards, Erik-Jan.
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Erik-Jan Geniets wrote:

It's a 1985 Chevrolet S-10 Diesel. It has the same engine and transmission as the Isuzu P'up Diesel of the same year. The rest of the truck is good old S-10, just the engine is different. And yes, this is the way it came out of the factory. It's even covered in the 1985 S-10 shop manual, but the illustrations SUCK!
It has the same 3 temperature sensors as my 1986 Isuzu Trooper Turbodiesel does on its C223-T, and the Trooper _does_ have both a temperature guage and a light.
Perhaps there is a sensor for a guage, and the wires just don't go anywhere? That would be typical GM.
I'm going to install a guage pack and a tachometer on the truck, and if there's already a temperature sensor for a guage installed then that would be a great help.
I stripped the guage pack out of a junk Trooper, and I'm going to mount it in a project box on the S-10's dash, where it should look right at home. I also got the oil pressure sensor, as the S-10 doesn't have an oil pressure guage either. Now all I need to find is a MFF T fitting in 1/8" British Standard Pipe Thread and I'll be set.
Thanks again, AP
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Alan Petrillo wrote:

Sorry for still not responding. Haven't done my howework yet on this. As soon as I will have some or find more info on this I will be back. Kind rgards, Erik-Jan. http://www.fotograaf.com/trooper
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