E3D aero hotend not heating to target temp

[Bohn1]

I have successfully installed the E3D Aero on my FT 5. I has worked for several months...very well, I might add.
Now....without understanding the cause, I cannot get the hotend up to temperature. For example, setting it to 185 C, it starts to heat up but stops at 104. I have replaced both hot end thermistor and heat cartridge, without solving the problem.
Just for the heck of it, I disconnected the hotend fan, and then was able to reach 185, without overshoot. When I reinstalled the fan, the problem re-appeared. Once I got the hotend up to temp w/o the fan, and while still running, installed the fan. The hotend cooled down and never reached 185.
Doublechecked both heater and thermistor resistance, and they comply w/specs (4 and 100K ohms respectively)
I checked heater voltage to hotend, and got 11.5 Volts. PS voltage is at 13 V. I checked all connections...they are tight.

When the system stops heating, in Pronetrface, I get:
Setting hotend temperature to 185.000000 degrees Celsius.
Error:Heating failed, system stopped! Heater_ID: 0
[ERROR] Error:Heating failed, system stopped! Heater_ID: 0

 Error:Printer halted. kill() called!
[ERROR] Error:Printer halted. kill() called!

I have tried using Cura, and got the same result. Same when using CONTROL with LCD.

I have disassembled the Aero, cleaned and reinstalled.

If this problem is not resolved, I'm considering looking into the wire run between hotend and MK 3 board. I hesitate to open that since it's an extensive process to open the cablechain and undo the wire braid.....but it may be my last resort.

Any thoughts on this would be welcome.

[csorrows]

When you say "hotend fan" do you mean the fan on the heatsink or the layer fan? If you mean the layer fan, it is blowing on the nozzle cooling it down.

If it is the heatsink fan, try doing a PID.

[Bohn1]

The heat sink fan. Part cooler fan is off.

[Bohn1]

Cannot run PID. It times out.

[csorrows]

Weird, I have never heard of a heat sink fan cooling down the hotend.

I would test the resistance of the heater wire before removing it from the chain. Also, move it around while testing.

[Bohn1]

Heater wires are .1 ohm each.

Your comment about a sink fan cooling down the hotend. Although the heatbreak looks good....if that's not functioning properly, that might be the problem....Hmmmm
Will check wire continuity while moving things around.

Thanks for your thoughts.

[MGD]

Is the cooling fan blowing into duct and then to the heatsink?

Tape a little piece of string to a toothpick and so if you are getting blow by on to the hot end when the heatsink fan is running. Just hold the toothpick so that the string is near the hot end and if the string starts moving around you’ll know there’s air getting blown on to the hotend causing your issue or not.