EMS Problems

[nearwater5]

I have installed the EFIS D100 and the EMS 120 in my RV7A. When powered up, the EMS readings go all over the place. For example the Oil temp and Pressure fluctuate from low to high, the OAT and Carby temp are wrong, Half full fuel tanks show full, CHT and RGT are very high and the Amps fluctates. After a reasonable time, it settles down and the readings start to look correct except for the OAT. The OAT reading on the EFIS is correct. I have made sure the battery is fully charged and have tried with a battery charger connected, to ensure there is no voltage drop.
Today I successfully uploaded the latest Firmware package to the EMS and seemed to make no noticeable difference ie the wrong readings and fluctuations are still happening. When I successfully uploaded the Firmware onto the EFIS, it lost its connection with the EMS. It seems strange that the EFIS worked fine on installation, but the EMS doesn't. Would appreciate any help. The plane is ready for C of A so pretty anxious to get this sorted.

Thanks
John

 

[dynonsupport]

A few things to check out based on leading causes of this behavior:

Stray voltage. Particularly, check where the 12V and 5V lines are going. If it's being injected somewhere it ought not be going, it can affect gauges all over the instrument. A way to test this is to make up a test harness that has ONLY power and ground. If that changes things, it's almost definitely not the instrument. Generically, though, this tends to be a misrouted wire somewhere.

 

[nearwater5]

I have checked the wiring best I can. What I can't work out is that the temps, pressures, fuel levels etc, are not correct when first turned on, then after 15 minutes or so, everything except the OAT reads accurately. If I switch the power off and on again after a short time, the EMS settles down quickly. I am wondering if the OAT is the problem, but it read OK on the EFIS.

 

[dynonsupport]

We're happy to take a look at the unit if you'd like, but if you haven't started disconnecting sensors and wires, you really haven't eliminated the possibility that something is going somewhere it shouldn't.

As for the OAT problem - where is your OAT probe connected? The OAT should only be set up in the software on the device that it's connected to. On the other, it should be set to none.

 

[nearwater5]

Thanks, started going through the sensors and found I had wired the MAP sensor incorrectly. Had the 5v and earth back to front. Changed them and all working OK.
OAT sorted too. Just running it through the EFIS.

Thanks Again
John