Knife connectors are not really appropriate for thermocouples. The resistance,
especially after some oxides have formed will cause the type problems you are
seeing. You might be able to temporarily fix the problem by crimping the
connector a little so it bites harder. You should however consider replacing the
kinfe connectors with ring lugs bolted together with a star washer between the
lugs as was suggested. If you do, you should also double the wire back to get
twice the thickness when inserting the wire and crimping it.

Newps wrote:

Dennis O'Connor wrote:
Two possible causes, Newps...
One is a broken wire(s) going to the instrument panel where moving the wire
around to work on the lugs causes the broken ends to abrade and make better
contact for a while, and then they reoxidize... This is high on my
suspicion list since it is the same two wire runs all the time.. Don't take
the lugs apart this time, simply give the wires a good workout and moving
around and see if that changes it..

All the wires are securely fastened within 2-3 inches of the
connections. So when I pull them apart there is no slack, they cannot
be moved any farther apart. Because of the plastic around the terminals
I can't get in there effectively to clean the terminals with say sandpaper.

If not, then the surface of your terminal lugs (stake on rings) are
oxidizing... If your hardware for the lugs does not have those little
stainless, star washers, get them...

Actually the terminals are male female slide in connectors. There are
no nuts, bolts and star washers.

Now, they do not go under the nut
(which we are all conditioned to do), rather they go between the lugs of the
two wires so that the sharp edges of the stars bite into the metal of both
lugs as you tighten the screw, maintaining a gas/oxide free contact between
the two lugs.. We are working with a few millivolts of signal, and it takes
almost no oxide at all to act as a resistor and block current flow...

Not sure what you mean't by 80 and 250 for EGT, so I suspect a typo...

No, that's the reading I get. 80 degrees F up to about 250F. And it
constantly jumps around between those numbers. Every once in a while
I'll get a normal reading of between 1250-1450F.

--
--Ray Andraka, P.E.
President, the Andraka Consulting Group, Inc.
401/884-7930 Fax 401/884-7950
email
http://www.andraka.com

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