ETLB Squawk Forums — Archive

Hi,
I'm halfway breaking-in the R277. Unfortunate happened when CHT has stopped working.
And obliged to abort the break-in program.
I really dont know how to check or troubleshoot this thing.
Do you guys has something to suggest or advised?
Thanks in advanced.

Phil

Hi Phil.

I take it the gauge worked for a while before it failed?

With a multi meter you can check for continuity across the 2 pins for the CHT. When checking you should get a reading of a couple of Ohms and you should also see the needle of the gauge move slightly. If the gauge doesn't move swap the probes around and try again. If the gauge moves than it should be ok so then check the connection of the wiring to the engine.

Hope this helps.

Cheers, Mick

I'm guessing a broken wire due to vibration of the engine.  Look at the wires where they join together at the ring terminal.

Thanks, Mick! I tested pins accordingly and found gauge ok.
Tracing for continuity a broken wire near ring identified..as Radfordc nailed it!
Now, I'm thinking of lead soldering to reconnect since wires were crimp to the ring.
This advisable?
Regards,
Phil

Hi Phil...try for the repair ...however once they fail..I find replacement is better...which cost $$$$ so take care of them from the start.

This is my experience..sorry for the bad news

My experience is to treat them very gentle. They seem fragile.

Good luck ..its good to see you making progress.

Regards Arthur

Ohh Ive replaced 3 on my aircraft..just info for you

A soldered repair won't work.  If you can open the crimp on the ring you can cut off the broken wire and recrimp the ring.  Be sure the two wires are touching inside the crimp.  I've found that replacement works best.

If you have a small hi temp torch you can melt the two wires together forming a small bead. Then any crimp connector will do.

The wires connection in the round connector is a thermocouple. Any soldering there or on the wires will change its properties and therefore the gauge reading.
Unfortunately, the only solution is to replace the wire with the thermocouple.

I opened the crimped ring with oxyacetelene torch to removed wire and recrimped the pair wire before lead soldering the wire tips. Considering a temporary set-up while waiting for new probe to arrived then it could be compared readings between repaired probe with new one.
Just finished or able to complete the engine break-in with satisfactory results.
CHT has shown the maximum temp of 410 F and 900 F on EGT.

Good to hear you found the issue.

Cheers, Mick

An easy way to check the calibration on a CHT probe is to put it in boiling water.  Temp should read very close to 100C (212F).

Weld, not solder!

Sorry, I have to go off topic, great dash.  I've done it in the past (and if you did it the same way double 👍)but I think it would be neat if somebody with more experience/communication skills posted a how too on machine turning.  Yours looks great