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EIS Oil temperature ??????

NYTOM

Well Known Member
For those of you who have the EIS 4000, does your oil temperature readings jump in large increments as you warm up your engine?
Just started Phase 1 and when warming up today I noticed a start temp of 59 degrees . Was waiting for at least 100 degrees and the temp stayed at 59 and then jumped to 121 degrees. I would expect to go up in a lot smaller increments of a few degrees each. Is this normal for the EIS 4000 or should I order a new sending unit? Doesn?t seem right. Contacted GRT but they may be Covid19 closed and I haven?t got a answer from them yet.
Any experience you can share is appreciated.:)
 
Dealt with same issue with fuel pressure

Tom...I had the same issue with a fuel pressure sender and EIS 4000. I don't know if the senders are the same architecture but GRT sent me a new sender and my bouncing readings were resolved. Good luck.
 
59 is as low as it goes, but above that should increase smoothly. If the OAT is above 59, the oil should read the oat without even starting the engine.
 
I'm not so sure. You state you are in Phase 1 so I assume the sensor is pretty new. The sensor is just a resistor that changes with temp. It depends on a connection of the threads for the ground.

Try a couple tests. When cold, the sensor has higher resistance (1000 ohms at 70F) dropping to 200 ohms at 140F and nearly 0 ohms at 320F. Try taking off the wire and you should see 59 on the GRT. If you have or can get resistors, try 200 ohms and see if it indicates 140. Try shorting the wire to ground and see if the indication is 300 or more.

The sensors are standard VDO units. There should be a number stamped on it, like 801/4/17. This a a VDO #323058 sensor available from a number of places on the internet.

My guess is you have a bad ground. If your sensor has tape on the threads that will cause a problem. Or if you have a remote manifold that the sensor is mounted on, there must be a connection to ground from the manifold.

Jim Butcher
 
Interesting Jim. Yes I do have resistors and I will try out the test procedures. I never use Teflon tape on the plane and only use Teflon paste but still will check the ground also. Thanks for the input. It?s phase one but the sensor was bought years ago in a deal at Osh and this was a slower build than I thought.
 
Is your sender a two wire, or one wire? The one wire sender grounds through the sender chasis to the engine case. The two wire has a dedicated ground wire that connects to the engine case near the sender with a ring terminal on any available bolt. Make sure your main engine case ground wire (2 awg) is secure, clean, and mounted to a good firewall/ground buss bolt.

Also, depending on your oil temp probe, you may either have straight threads, or NPT threads. If your install uses a copper/asbestos crush washer, you have straight threads. You don’t use a thread sealant of any kind on straight threads if the threads provide your ground pathway. The copper gasket/washer (most likely AN900) provides the seal, and be careful not to over tighten. I just installed one of these last week on a Grumman. That one had 5/16-18 threads and it should be finger tight +135 degrees of torque. That’s not very tight, but it’s a reason you have it safety wired. Teflon sealant on your threads might be limiting your temperature readout. Don’t reuse those copper crush gaskets.
 
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Tom,

I forgot to suggest, take out the sensor and use a ohmmeter to see how the resistance changes while you heat the sensor in water on the stove.

Jim Butcher
 
Before I remove it I?m going to check resistance between the sensor body and the aircraft ground as Scott mentioned. Then I?ll try Jim?s suggestion of continuous resistance readings while heating the sensor. It will be interesting to see if the sensor readings jump in stages. This should isolate the problem. Now I?m mad at myself for not thinking of these tests myself.
This site makes it to darn easy to run for help. Thank you :)
 
So?

NYTOM, what happened in the end? I?m chasing an intermittent oil temp issue and I have myself nearly convinced it?s not a grounding issue to either the engine to chassis/batt or EFIS to chassis/batt grounding problem.

I?m coming up scarce on information on a two wire sensor that does not use case grounding, but still has the same resistance/temp curve. Can somebody point me in the right direction?

Thanks
 
For those of you who have the EIS 4000, does your oil temperature readings jump in large increments as you warm up your engine?
Just started Phase 1 and when warming up today I noticed a start temp of 59 degrees . Was waiting for at least 100 degrees and the temp stayed at 59 and then jumped to 121 degrees. I would expect to go up in a lot smaller increments of a few degrees each. Is this normal for the EIS 4000 or should I order a new sending unit? Doesn?t seem right. Contacted GRT but they may be Covid19 closed and I haven?t got a answer from them yet.
Any experience you can share is appreciated.:)

IMO, that behavior points to an intermittent connection. I would start by checking the wire and re-crimp the connector at the sensor.
 
NYTOM, what happened in the end? I’m chasing an intermittent oil temp issue and I have myself nearly convinced it’s not a grounding issue to either the engine to chassis/batt or EFIS to chassis/batt grounding problem.

I’m coming up scarce on information on a two wire sensor that does not use case grounding, but still has the same resistance/temp curve. Can somebody point me in the right direction?

Thanks

I had an EIS provided O/T sensor that gave low readings and somewhat intermittent, though not jumpy or erratic. Upon investigation, I found that the composite/epoxy that holds the thermistor inside the brass shell had gone bad or had poor adhesion and the small S/S probe inside the brass shell was loose anc could move up and down. The lack of adhesion and resulting air gap was causing the low readings. I cleaned it out and re-bedded it with JB Weld and all was good. I think this was a QA issue with the EIS sourced sensor.

The thermistor shell must be in contact with the brass in order to give good readings. A quick tug on the wire into the sensor will tell you if you have this issue.

Larry
 
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