Identifying False Junctions in Exhaust Gas Temperature Probes

Identifying False Junctions in Exhaust Gas Temperature Probes

Customer Question:
One of my EGT Probes is measuring about 300C lower than the rest. What is happening? What we suspect is happening is that the EGT probe has developed a “false junction”.

Answer:
The primary measuring junction of an EGT thermocouple probe is the tip. This is where the 2 wires meet & are welded together. If these two wires touch at any point other than this junction before it plugs in to your gauge or controller then this second junction would be the “false junction”. The result is that the temperature reading becomes an average of the two junctions.

So, if your temperature in the manifold where the probe tip is installed is 800C & the “false junction” is somewhere in the cable near the engine where it is 50C, then you could get a final temperature reading from the probe of 425C.

We suggest you thoroughly inspect the EGT probe’s cable to make sure there are no cuts or kinks. Also look inside the connector plug on the end of the wire to make sure there is not a short.