*&^%$ EGT Probe crimp

[swatson999]

For about the 5th time, I have a probe which has a wonky crimp (obvious because the EGT values are jumping all over the place, rapidly, from essentially zero to off-scale high).

Each time this happens, I re-crimp the little bugger, and it works fine. But why am I getting these failures, and how can I prevent them? I know soldering is a bad idea. The connectors are all well-insulated, well-supported, held in a bundle with an Adel clamp to the engine mount to reduce vibration, plenty of service loop in the wires, etc. I'm running out of ideas here...

This has happened now on at least 1 CHT and several EGTs...

 

[jc2da]

For me, it is not the crimp that is flakey but the actual blade connector. The hot and cold cycle seems to work the connector looose.

I bend the male blade a tiny bit to add some spring pressure. I also throw a heat shrink over the connector to keep everything tight. No flakeyness in 200+ hours.

 

[jdubner]

For about the 5th time, I have a probe which has a wonky crimp

I have had the same problem with one particular probe line.  The bad crimp was in the factory part (probe end) and no amount of crimping seemed to help long-term. 

I think these particular spade connectors are a poor choice because they do not have a metal sleeve in the insulation grip area.  A crimp in the plastic insulation grip area quickly relaxes and loses its effectiveness.

I tried soldering but the thermocouple wires did not take solder so I quickly abandoned that idea and used a genuine PIDG butt splice with two good crimps.  It has been trouble-free ever since.

 

[jakej]

Guys,

FWIW - I've also had various problems like yours however there is a solution.
If the probe wire is a single conducter, as have been supplied at times, then you need to strip back the insulation and bend the wire back so that there are 2 pieces entered into the crimped terminal.  The single conducter is too small to be able to be crimped satisfactorily.
If the probe has a multi cored conducter then that is much easier to fix.

In both cases above I buy the AMP brand of connectors for the loom & probe end as they a slightly 'softer' which allows a much better 'squeeze' IMO.  The dark red coloured female ones supplied on some probes are just not aviation quality & the pink coloured male ones are too hard to crimp properly 

It took a while but once I 'discovered' the solution to these & other thermocouple issues, I don't now have any  :

HTH

Jake J