Amps Draw Indication

[Tackdog]

Hi,

My HDX system has recently shown a bizzare indication for the amps draw. The shunt is installed in position B. The EMS LED is flashing fast red, the network config says the EMS is status: ready with no faults. The EMS was recently replaced.

When only the HDX is powered, the volts show 12.4 and 47amps

When the alternator fields are turned on 12.4v and 72amps

When the engine is started and other items turned on
14.1v and 79 amps....

Naturally there is now way the system is drawing that amount.......

Any suggestions?   

 

[airguy]

Check your connections on the shunt, this sounds like a low-resistance weak connection.

 

[Tackdog]

Check your connections on the shunt, this sounds like a low-resistance weak connection.

The shunts resistance is fine and all connections and continuity is fine. When the 2 wires are shorted it still reads the 47 amps...

 

[vlittle]

Check your connections on the shunt, this sounds like a low-resistance weak connection.

The shunts resistance is fine and all connections and continuity is fine. When the 2 wires are shorted it still reads the 47 amps...

This is a contradiction... if you are shorting the wires for this test, there are still at least two connections involved... check the dsub pins in the main EMS connector by removing the connector shell for inspection. I had two harnesses where a pin was not fully inserted.

If this checks out, pop out the two amps sensor pins and see what reading you get. If it doesn't change, the EMS is damaged. If it does change, keep looking for wiring problems.

Vern

 

[dynonsupport]

Vern's observation is a good one. Upstream wires being broken can cause readings like this. However, they do generally change somewhat as you change other wire connections.

If you can, try shorting the shunt input at the EMS.

We have seen some inputs be broken over the years, so if it doesn't go to zero when you short it, then it does likely need a repair.