The hot gas eats through these eventually…
Initially what you get is an intermitted EGT fluctuation. That might be an indication of a sticky valve, so one needs to keep an eye on it, and check the CHT is holding steady and normal.
Then you get an abnormally high reading e.g. +2000F and together with a normally running engine and a normal CHT this indicates an EGT probe that is about to go open-circuit. The reason an o/c probe reads high (and not low as one would logically expect) is because thermocouple instruments traditionally try to detect an open (or missing) probe by having a pullup resistor on the input (to maybe something like +5V) which produces an abnormally high reading if the probe is missing.
Eventually the instrument realises what is going on and flags that probe as duff.
In the pic above, the CHT reading only remains.
The probe will be changed at 8:30 this morning 
Interestingly the US price is $104 while the European price (link above) is €106 Even though the Euro price includes VAT, I am considering going into the foreign exchange business…
Is anybody interested in doing a bulk buy from the USA? I will be getting six of them.
Interestingly the US price is $104 while the European price (link above) is €106 Even though the Euro price includes VAT, I am considering going into the foreign exchange business…
You get it shipped via air freight and you get German internet purchase 14 days return no questions asked and 2 years of warranty. I think that aircraftspruce.eu has very fair pricing. You will pay significant shipping for getting the probes from the US and very often I need small but uncommon parts which aircraftspruce.eu get me in less than a week at very reasonable cost. I am glad they exist.
When my last EGT probe failed, I just got one from them and replaced it. No need to stock 6 of them and have the capital cost of 5 unneeded probes!
Fair points and I agree spruce.eu is a useful supplier… however I think EGT probes are like light bulbs in that if you have six in the same room, and one goes, the others tend to soon follow, so I will change the other 5 at the next 50hr service. Getting the bottom cowling off is a 2-person job and a huge hassle.
BTW the probe itself is $59. The Q is whether you want to take a risk on re-using the jubilee clip, which has been heated up to a high temperature over many cycles. I don’t think it is worth it. The probes last at least 10 years.
The other approach are the EI probes which are electrically equivalent but I don’t know if they go into the same hole in the exhaust pipe. They are claimed to last much longer than the JPI ones.
We put in the new probe
No difference! I thought … bugger. It will be a broken wire or worse still a broken input channel on the EDM700.
It turned out to be a duff probe. Straight out of the bag. TSOd, with an 8130 of course. They might test them at some stage in the production but they certainly don’t test them when they are finished… Luckily I had two spares.
As an update, JPI have totally washed their hands of this, saying that
Nice customer service!
I’ve found the JPI’s customer service is generall pretty poor. They can’t realloy be bothered with after sales service. I wish I had stuck with my original GEM – Insight is a much nicer company to do business with!
They also have better protected probes, which should last a lot longer, and should be 100% compatible with the JPI indicating instruments.
He says… having just bought 6 spare JPI EGT probes
But I think the EI probes need bigger holes in the exhaust pipes.
I don’t think there is anything actually wrong with the JPI instruments – apart from them being late-1970s technology, but then most of the little individual instruments we fly with are from that era.
I have a theory about companies like JPI, and that is that one can guess the quality of their customer service by reference to (i) their website a little, and (ii) their products’ pilot’s guides a lot. If they can’t be bothered to set up an easy to understand narrative with customers through the written word then they are unlikely to be good on the phone or by email.
JPI’s pilot’s guides are awful. The current one for the EDM 700/800, at pages 26 and 27 “explains” how to set the current fuel level at start up for the EDM’s fuel functions but I think in fact these pages are in fact designed to confuse existing users of an EDM 700 and for no other purpose :D. Truly shocking. In my opinion these pages and others represent an excellent example of how not to explain things to people who have bought your product.
…oh yes, I have a six month old EDM700 installation with an already faulty temperature probe that failed during the annual and then started working again. My guess from Peter’s comments that it’s on its way out.
No prizes to JPI then.
Howard
Video of a JPI EDM700 EGT probe about to fail
This is what you get when it finally goes, when the EDM decides the data is rubbish. You get just the CHT displayed
I have just bought 8 of them so will probably change all six, because they tend to go together, more or less… 50hr service tomorrow…
Well, your cylinders look nice and cool… 328°F
