OAT EGT problem

[Epiphyte]

I have a b&d combined oat egt gauge in my 1981 m20j. The oat works great, but the egt is pegged at lowest reading, in other words, is not working. Mechanic checked wires at firewall and probe. They seem fine. Not sure if I lost a ground wire behind the instrument or what is wrong. Anyone have experience with this problem?

S/N 49619

b&d p/n 0203-007

Cust p/n 880001-501

Also, I noticed that some have wire harness plug only while other similar gauges have a black and white wire attached to the back of gauge

Thanks

Troy

[carusoam]

Physical inspection of the probe is relatively easy.

They have a tendency to burn through.

But a mechanic should know this already....?

Good luck,

-a-

[MHemperly]

Bad probe^^^

[Bob - S50]

Should probably buy a 4 cylinder EGT/CHT system.

[Epiphyte]

Thanks for the replies. The probe had been inspected and looks fine, but I may have it replaced anyhow, just to be sure.

I wish I could afford a 4 cylinder system, bob. I'm barely able to afford insurance, hanger fee, fuel, and maintenance....but I find a way to eek by.

Should the screw on wire harness be the only thing that hooks up to the gauge? Anyone know what the black/white extra wires are for? Seems weird that they would both be for grounding.

[bonal]

Agreed. I think some times some of the folks on this site forget that some of us are making a huge sacrifice just to have the privilege to own any kind of aircraft. I to would like to install a fancy engine monitoring system but its way out of my budget. I figure my aircraft has lasted 50 years with its stock systems as long as I use good judgement it should go another 50.

[carusoam]

Everybody is making a huge sacrifice...

Some more than others.

Hang in there. It should be worth it when you make the right decisions.

We are all on the same path.

Some have been here longer.

Some have just gotten started.

Some graduate to the next level.

Some won't graduate for some time.

Some fade and then come back.

Some have their planes or themselves get injured. See the support they get. Watch how they come back!

The advice you get may not fit your situation, but it is most often given with enough information to help you decide whether it fits or not.

I get it. My C didn't have FF, GPS, or an engine monitor... But, the engine monitor would have nearly paid for itself the first year...(stuck valve= cylinder replacement). Unfortunately MS was years in the future when I started.

Monthly day care costs (in NJ) are more than monthly Ovation costs.... You know which parent was the happiest at kindergarten graduation!!!

The path is longer than you think, stay on it!

-a-

[Bob - S50]

Agreed. I think some times some of the folks on this site forget that some of us are making a huge sacrifice just to have the privilege to own any kind of aircraft. I to would like to install a fancy engine monitoring system but its way out of my budget. I figure my aircraft has lasted 50 years with its stock systems as long as I use good judgement it should go another 50.

I'm right there with you.  That's why I have 3 partners instead of owning the plane myself.

 

Bob

[bonal]

No disrespect meant. I hope that I will be able to stay on the path I started with my 150 to train and when it was time to make the first step up I wanted the best plane I could afford and for what a 172 or Cherokee would have cost I stepped into the world of Mooniacs.

I love to fly our mooney and always feel a lot of pride when we visit other fields because she looks so awesome on the ramp.

It would take a major change in finance to move into the world of the "modern Mooney's"

But one never knows

[MHemperly]

Epiphyte, the probe may look good to the eye but in most cases they have an internal problem. I just replaced mine a couple months ago and it looked brand new. I literally watched it go out. The EGT needle bounced a couple times and went cold. You have to remember the temps these things see on every flight. Probes going bad is a common thing. As far as the wiring you should only have the two screw on wires going to the probe and whatever wiring there is for the back light on the gauge. Very simple system.

I'm right there with you guys on the budget! I would love to do so much to our E but there just isn't enough Benjamin's in my bank roll haha! A good way to see how you are running your engine (this is how I do it until I can get an EDM) at altitude, lean until you get a drop in rpm, then richen about two turns and let it settle and then run 50-100 degrees rich of whatever it settled at. And then do your own oil changes. I find this very helpful because I was thought at every oil change (50hrs) you clean and gap the spark plugs. This gives you a chance to see how it's running by the color of the plugs, white is way to lean, black is on the rich side which is fine if you want to burn the fuel, and a dry dark grey is pretty good. Also do a compression check while you are there. And don't forget to put an additive every 100hrs.

[scottfromiowa]

I now have a co-owner and that literally allowed me to stop donating blood plasma for the priviledge of Mooney ownership. I gladly did the Plasma donation as it allowed for "a little guilt-free" extra going toward upgrading my Mooney. I bought a Gem 602 used on ebay for about $200 bucks...saved and bought the probes...saved and bought the install. I look at shoulder harnesses, multi-probe EGT/Cylinder monitor and audible gear alarm/stall alert as reasonably priced potentially life saving essentials in the 21st century...not luxuries...like park assist and lane management in autos and now flat-screen in aircraft. I would also say fuel flow is now in that category. Co-ownership was the key that has made Mooney ownership a pleasure instead of Mein Kampf.

I have followed the AOA threads and just shake my head as the pre-stall and gear alert was peanuts including install WAY under the $1500 for an AOA purchase/install. I had one time hearing "Stall" in my headset other than in the flare. It was a wind shear situation that MADE MY DAY alerting me on short final that all was NOT all well.

[Epiphyte]

Thanks for all the great replies....and, bob, I will be looking for a partner soon. You all have very good points about the value of saving money by sharing costs.

As for the gauge, I'm pretty sure those wires are for the back lighting, that makes sense. Now I really will be changing out the probe. I'll let you all know how it goes. Thanks again for your valuable time.

[Bob - S50]

Thanks for all the great replies....and, bob, I will be looking for a partner soon. You all have very good points about the value of saving money by sharing costs.

As for the gauge, I'm pretty sure those wires are for the back lighting, that makes sense. Now I really will be changing out the probe. I'll let you all know how it goes. Thanks again for your valuable time.

Best of luck finding a good partner or partners.  With good partners you'll really enjoy the cost savings and the options it makes possible.

 

Bob

[bonal]

Well I'm sure a partner would save some money maybe not the plane would accumulate hours at twice the rate or more. And to be truthful I would not care to share my beauty with another man any more that I would my beautiful wife. As a life long biker no one dares throw a leg over my bike. Same idea. I live within my means and am very lucky to not only have my own airplane but more importantly the passion of flight.

[Bob - S50]

Well I'm sure a partner would save some money maybe not the plane would accumulate hours at twice the rate or more. And to be truthful I would not care to share my beauty with another man any more that I would my beautiful wife. As a life long biker no one dares throw a leg over my bike. Same idea. I live within my means and am very lucky to not only have my own airplane but more importantly the passion of flight.

Glad to hear you can afford the plane yourself.  I wish I could justify that for me.  The plane will in fact accumulate time faster, but that could actually be good.  Too many planes do not fly enough or often enough.  Having a partner helps fix that problem.  And it is true that you will get to overhaul sooner, but you'll have someone to split the cost so $/hour will be the same.

 

Of course, just like your beautiful wife, you have to find the right partner.

 

Take care,

 

Bob

[Pattyler]

I have 1978 m20j. My b&d egt/oat also dead on EGT side. Mine has eight pin barrel connector. OAT came back to life after we disconnected and reconnected barrel, so probably corrosion. EGT still out of service. Cannot find B&D Instruments replacement. What is best option? 

[carusoam]

Welcome aboard @Pattyler.

Have you come up with an answer to your sensor challenge...

Many people have gone with JPI or EI or insight for upgrades.

Best regards,

-a-

[skykrawler]

EGT probes generate a very small voltage  (0...55mv, linearly) when they are heated.  This can actually be measured with digital volt meter.   Carefully heat the probe with a propane torch and monitor the voltage across the leads (disconnected).

The B&D instrument could be tested with a power supply that can produce millivolts.  Start at zero and slowly increase.

I repaired my B&G OAT side by diagnosing and replacing a bad diode.  But the OAT sensor is different than the EGT.   The EGT probe may drive the needle movement directly.

[Thomas Weber]

For my Information. Is your aircraft on 14V or 28V? 

 

We do have almost the same problem

 

Kind regards 

 

Thomas

[carusoam]

Welcome aboard, Thomas...

I can’t tell who you are asking the question to...

But I know most EGT probes aren’t powered by an external source... he thermocouple produces the mV required....

In the odd case of a thermistor being used for CHT... Mooneys have a couple of years of doing this...

Are you referring to the EGT not registering, or the OAT?

Expect it to be the most simple instrument possible, with simple probes... and grounds being dirty will cause low powered probes to fail easily...

PP thoughts only, not a mechanic...

Best regards,

-a-