Carb temp sensor reading very high

[Geoff]

G'day Dynon

I have a D180 that is near completion of installation at present.

The carb temp on GP2 is reading 79C when it should be reading about 23C.

I have disassembled and double checked all connections.

The sensor is the one with 2 black wires.

The 5V excitation circuit is producing 5V, I have the 1K Ohm resistor fitted and it is testing at 1.54V downstream from the resistor.

Your latest instructions call for this resistor to be colour banded brown, black, black, brown, brown ..... however I don't have any in your package like that. Mine are colour banded brown, black, brown, brown, brown, so I have just returned from town where I bought a new 1KOhm resistor which is identical to the latter banding with a blue body.

Where have I gone wrong and what do you suggest?

Regards Geoff in Wagga
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[dynonsupport]

A few couple of thoughts:

79F is about 26C - is it possible that the units are set to F under the EMS|SETUP|GlOBAL menu?

One quick check to see if you've got any semi-valid connection at all is to heat or cool the sensor a bit, and see if this produces a change in temperature on the FlightDEK-D180. Also, our latest installation guide, available here, has a diagram that makes the 5V connection a bit clearer.

Also, double check that the sensor is physically connected to GP2, that GP2 is set to carb air temp, and that the sensor type is set to type 1.

 

[Geoff]

Thanks for your quick response.

The global setup was at C and the Carb Temp gauge said C below it. I have just also done another global set to C, just in case.

As per my post, I have the latest version of your installation instructions and used your latest diagram to double check the way that I have installed the sensor.

I confirm that that the sensor is definitely hooked to the GP2 purple & yellow wire, that GP2 is set to Carb Temp and that it is set to sensor type 1.

I also confirm that when heated a little the sensor reading does fluctuate upwards by what looks to be roughly a correct amount.

This morning the OAT and other temp sensors (EGTs & CHT's etc) are all reading 24 - 25 C while the carb temp sensor is reading 82 C. You will note that they are a couple of degrees up from yesterday, and so is the carb temp reading.

NOW ..... I still need your expertise to solve this ..... however please also confirm whether your latest instructions are correct which state that the resistor must be banded "brown, black, black, brown, brown", as that is not the one that I have. Is that correct or am I correct having the resistor that is banded "brown, black, brown, brown, brown".

Please also confirm whether the 1.54V reading downstream of the resistor is correct.

Also .... I think (but would need to double check) I recall that the sensor with the double black wires was a VDO unit. Is that correct & might that mean anything to you re this problem.

I look forward to your further advice.

Geoff

 

[dynonsupport]

The resistor we supply is 1000 ohms. The one you have is 1010 ohms. This won't make much difference.

If the resistor you have is br, br, br, bl, br, that's 111 ohms and makes a huge difference!

1.54V = about 80 deg C, so this means the EMS is reading the voltage right.

I note that if you didn't have the resistor actually pulled to +5V, you would get exactly the results you are seeing. Are you sure you have your resistor hooked between the GP pin and pin 18?

 

[dynonsupport]

Also, double checking the actual resistor value with a multimeter (measure resistance across the resistor with power off) might help confirm what resistor value you have there.

 

[Geoff]

Thanks very much for your 2 extra responses.

The problem is now fixed and it was, indeed, the resistor capacity.

As I am just a simple "lever & fulcrum" kind of guy from a mining background it took me a while to determine that the original resistor was wrong, the replacement resistor was sold to me as a 1K Ohm unit but was incorrect capacity too .... but after studying resisitor codes in detail and hunting through the boxes of resistors at the store I ended up with the right one and the Carb Temp reading is spot-on.

Thanks again for your help and apologies for bothering you.

Geoff