I am ready to install an Autometer Pyrometer in '07 F-250, the problem I have is with the thermocouple. I purchased an Ultralight II model because I liked the looks of the guage. When I received the gauge, I noticed that it did not have a NPT fitting included, it only came with the clamp-on style fitting which I do not want to use. I went back to the vendor and they sent me a new thermocouple for an ISSPRO pyrometer. The new thermocouple has the NPT fitting I want but the leads on the new probe are short that are meant to be connected to another harness. The probe for the Autometer gauge are one piece and the instructions clearly state that the harness is calibrated for length and cannot be shortened or lengthened. The probe diameters are different so I cannot use the NPT fitting on the other probe.

My question is can I splice in the ISSPRO probe into the Autometer harness so that the overall length is the same? The wires between the two probes aren't the same, so it won't be perfect anyway.

It took over 4 months to get the new probe from the vendor, so I'm reluctant to go back to them.

Anyone got any suggestions?

Thanks,
Chumley

 

The first problem that I see here is that if the wire are not the same it is most likely that the thermocouples are not the same. The gauge is going to set up to read one style of thermocouple (type E,K etc.) Each style of thermocouple has different colors of wires associated with it. Each color of wire represents a different metal. If you mix the differnt types of thermocouples the reading will be off.

 

What color are the wire on both leads?

 

Each thermocouple uses a red and yellow lead. The wires on each thermocouple however are different sizes. I'm pretty sure the impedence difference alone will cause bad readings. At lunch today I went out and found a NPT fitting that should work. I should be able to use the original thermocouple that came with the gauge.

Thanks for responding.

 

Red and yellow leads mean the thermocouple is a type K, the leads are made of the same materials as the thermocouple sensor so you cannot use wire made of other materials to extend the leads. Red is always (-) negative. The max temperature range is
(-328 to 2282°F). Due to the short run, the size or gage of the wire will not affect the accuracy.

If you need to extend the length of the lead you could use a section of the other red and yellow wire, even if the wire gage is different. Splice the red to red and yellow to yellow; Do not use wire nuts to splice the wire because the dissimilar metals will affect accuracy, just twist tightly together and tape until you can order type K thermocouple wire and a terminal so you can terminate properly.