High Oil Temp when Coming in to Land (Long)

[lr172]

Originally Posted by Darren Kerns

I can try that too. I talked to AFS and Plane Power yesterday again.

AFS said turning off my alternator field cb and it goes to reading normal is a smoking gun something is going on with the alternator.

Plane Power said the same thing. I told Plane Power that during normal cruise I am only showing 13.8 voltage & oil temp is normal. The tech guy from PP said I should be higher on voltage. When coming in to land & decreasing rpms and oil temp going crazy is another sign something internally is going on inside the alternator. It does not do it during high rpms.

I will look again at my sensor ring terminal. It looks really good. I truly feel it is not my sensor because turning the alternator cb on & off while in the pattern shows wild fluctuations of oil temp readings.

Everything goes to normal when turning it off.

I have ordered a new PP alternator & I hope I have not made a stupid mistake of just throwing money at it.

I will post what the results are after installing it. I cannot install it until late next week.

I want to Thank Everyone who has contributed ideas.

Thanks Again
Darren Kerns
RV7 N599DT

Hope it works out. However, I would still remove and clean the engine ground strap and test again. I would expect a failing alternator throwing out noise to create issues with numerous sensor, not just the oil temp. While it is likely you alt is going south (low voltage), you still may have a problem with your engine ground and would explain why only OT sensor is having issues. Does you engine crank slower than it used to? That is a good giveaway that you may have a grounding issue.

Larry

[F1Boss]

Changing the diode board is very easy - and not very expensive. Might be that you can change that part and fix the problem without buying a new alternator? In any case, have an alternator shop rebuild your current alt if you decide to install the new one. Having a spare is a good thing.

[jdeas]

The diode is not the only possible issue. Visually check the leads from the Stator coil. You should see three solid copper lines. Due to vibration I have seen these break. If one of the three lines breaks you will get some noisy DC charging that can drive you nuts with the single ended sensors and radio noise. Other side effects include a lower charge voltage (but still higher than batt)

On my PP Alt, I was able to see the broken wire through the cooling slots. Was no need to disassemble.

[Darren Kerns]

Thanks guys for all of the advice.

I will definitely look at the ground strap again. I want to take it off and look at it closer and definitely get it cleaned up.

I will look at the stator coil too. I never even knew to do that.

Again, I want to Thank Everyone that has thrown ideas at me. I appreciate all of your wisdom and knowledge.

Also, Doug, Thank You for having such a wonderful website. Many of my problems have been solved by others contributing their thoughts and ideas.

Respectfully
Darren Kerns
RV7 N599DT

[N1Flyer]

Originally Posted by Darren Kerns

I have been experiencing an high oil temperature indication when coming into the pattern to land. I have AFS 3400s screens with engine monitoring sensors.

My oil temperature sensor was replaced at 310 hours and now may have to be again at 344 hours. During climbout and cruise it seems to be indicating fine. It is running a little warmer but it has been extremely hot here.

I called Rob and he told me to check of my wiring to and from the engine. So tonight my wife pulled both cowls and checked the engine ground to airframe wire. It had some oil on it but I cleaned it up and refastened. No crimps were lose. I checked all wiring to & from the alternator it seemed fine. Nothing lose. I then climbed underneath the panel and check breakers, crimps, and wiring and found nothing lose.

Rob suggested I turn off the alternator field and see what it did. My oil temperature was indicating 266 degrees and when I turned it off, it dropped to 187 within seconds. It seems I have some type of electrical interference.

I am getting so frustrated because I do not know what else to look at.

Can anyone help me to look at something else I have not thought of? I am going to order a new oil temperature sensor from AFS. However, this may not fix the problem.

Sidenote: When I replaced it back at 310 hours it was doing the same thing. I installed a new oil temperature sensor and it fixed the problem.

The other day when I was flying my 7 my oil temperature jumped to 366 degrees & then dropped to 204 within 2 seconds. This was without me turning my alternator field off. This is impossible for oil temp to change that much in 2 seconds.

Please, if anyone can give me some advice I would greatly appreciate it.

Thanks
Darren Kerns
RV7 N599DT

Darren, I had a similar issue with my oil temp sensor and my AFS-4500 during Phase 1. After lots of futile troubleshooting, I finally talked with Rob and ended up buying a new two-wire sensor from AFS. Wired the ground side directly to my common ground point on the airframe, problem solved.

Rick
RV-7A

[Darren Kerns]

Well, I finally fixed my high oil temperature reading problem. It turned out to be the ground strap from engine to firewall.

Installed a new PP alternator & AFS oil temperature sensor for nothing. Oh well, lesson learned!!

Thank you all of the help and wisdom.

Darren Kerns
RV7 N599DT

[ao.frog]

Hi Darren.

I'm glad you found the reason for your problem! Good job!
But I'm wondering if you can tell us exactly what was wrong with the ground strap? Partly broken? Bad connection in one or both ends? Loose crimp on one or both terminals?

It'll be interesting to know and a leasson learned for us I'd guess...?

Thanks.

Regards Alf Olav

[Darren Kerns]

One of my crimps was not tight. I did not notice it the first time and I just missed it. It was dirty with oil and the heat shrink had come off on one of the ends. I have no idea how but it did.

I cleaned both ends up and re-crimped them both. I put new heat shrink of both ends and it looked brand new when all done.

I re-installed and good as new. I am just mad at myself for not noticing that there was just a little play in one of the ends.

Oh well, lesson learned.

Take care and stay safe.

Darren Kerns
RV7 N599DT

[rv8ch]

Originally Posted by Darren Kerns

One of my crimps was not tight. I did not notice it the first time and I just missed it. It was dirty with oil and the heat shrink had come off on one of the ends. I have no idea how but it did.
...

I think this is why Bob Nuckols recommends two ground straps to the engine - he said that this kind of thing happens a lot. And if your ground strap comes completely loose, and you try to start the engine, you will fry something else as the electrons try to find another path.

At least now you have a spare alternator for when this one fails!