MGL Extreme EFIS everything reads low

[rtro461]

My MGL Extreme gives low reading on everything going through the RDAC. This is the Sonex Aerovee package from Sonex so everything was from them and MGL including the wiring harnesses The only correct temp reading is the OAT but that goes directly into the EFIS. From the first power on test all the EGTs, CHTs, and oil temp read about 30 F in the unheated hanger at 45F. Power and grounds check good. Setup is per the MGL instructions for Aerovee sensors.

MGL suggested putting a probe into boiling water. That read 185F on the EFIS. The K type thermocouples read correctly on my new TC temp meter bought to test the probes. The oil pressure didn’t seem right on my first engine run so I tested it with air pressure. 60 psi in reads 42 on the EFIS. 80 in reads 60.

So all the correct signal inputs in to the RDAC read low on the EFIS. After several weeks going back and forth with MGL I pulled the units out and sent them in. MGL said they bench tested them, found no fault, declared them good and charged me since there wasn’t a warranty fault. I asked if they tested the accuracy but they didn’t respond. Also asked what installation error would give low readings but no answer yet. Got the units back and reinstalled today. Same problem.,

Has anyone else had accuracy problems with the new MGL Extreme package?

[Onex107]

I didn't have a problem with my installation. Except after I put an air inlet on the side that put outside air directly into the on the RDAC. All the thermocouples read low. I covered the cold junctions with tape and the problem went away. That doesn't sound like your problem. There are dip switches to be set on the RDA C. Are those set correctly?

[sonex892.]

It sounds like you probably know and have tried the following already but this is what I would look at.

Are your settings correct in the menu? Mostly they are type K. Have you checked the results on type J or E settings?. Sometimes the polarity colours can be confusing, I have seen red for negative.

Are the display settings correct for your pressure sender? I dont know what aerovee supply, but there are 3 types of sender in the menu, voltage, current or resistive. VDO senders are the most common, they are resistive and have the pressure rating in bar stamped. Need to select either 2 bar, 5 bar or 10 bar. If the incorrect bar rating is selected it will still work, but display an incorrect reading. This is possibly your problem with the pressure sender. If not, you could just select user instead of the brand and calibrate it yourself.

A dedicated ground wire from the rdac to the engine can be important for engine analog inputs. The pressure sender and oil temp both rely on a good ground. Do not rely on grounds through the structure and or battery to engine cable for instruments. Poor grounding probably wont make any difference to your thermocouple readings.
Steve

[BRS]

dido that last post. Improper grounding was the first thing that came to mind.

[rtro461]

Power, grounds, and harnesses test good. Settings are per MGL’s directions for the Aerovee sensors. MGL thinks the RDACis bad and is sending me another one. It should be here next week and hopefully the instrumentation will work correctly.

[rtro461]

This is just my frustrations coming out today.

The second RDAC did not correct the low reading problem. A week after notifying MGL of this they haven’t responded. I have now asked them to just send me a new EFIS. I sent a copy of the request to Sonex just to make them aware of the problem.

I am of the opinion that there is a software program issue with the inputs to the EFIS. I originally ordered the package in July with it supposed to be in stock. The various pieces showed up except for the EFIS which was then not available. I was told by MGL that the computer chip shortage required them to redesign the unit to use chips that were available. 4 months later I got the unit. It took

It’s been three months of discouraging back and forth with MGL testing and trying different things without success. The Sonex is nearly done but I am rapidly losing interest. The progress has slowed down and the airworthiness inspection has been pushed back a couple months. If I get a replacement unit and it has correct readings it will be a happy day. But today I just keep pondering how much work it will be to rip everything out and start over with a different arrangement.

[13brv3]

It would be nice if they had confirmed that it read accurately when on the bench. Of course when the reported issue is "accuracy", how could you NOT test that. My only suggestion might be to recreate their test. Put the EFIS, RDAC, and a sensor or two on the bench. Power them by a standalone 12V battery, and check the accuracy. That 100% eliminates any possible influence from the aircraft wiring.

Good luck,
Rusty