dual extruder upgrade problem

I have upgraded my Hictop 3DP08 to dual extruder. It now has 2 extruder stepper motors and XCSOURSE dual J head nozzle extruder kit which has 2 nozzles, 2 thermistors and 2 heaters.

I have configured the Marlin firmware and uploaded it but I must have something wrong because the second heater will not come on. Both thermistors and heaters work ( by swapping out ) but it's like there's no power from the motherboard for heater 2 so I get the expected MINTEMP fail.

Can any one suggest what would be wrong with my firmware settings? I can't believe the motherboard is faulty but is there a way to test it?

Thanks in advance..

MINTEMP fail is the thirmistor not reading room temperature... heating will be disabled till this is fixed.

Thanks for the tip. I think the information I gave you was slightly misleading.

This is my scenario...

I am confident that all the hardware ( both thermistors and both heaters ) function correctly all the way to the motherboard but for some reason heater 2 will not turn on.

If I use the LCD control on the printer and turn up the heat for heater 1 I see the LCD target temperature set and watch the thermistor reading climb to the required temperature.

If I use the LCD control on the printer and turn up the heat for heater 2 I see the LCD target temperature set but the thermistor reading stays at room temperature. Then after around ten seconds I get "Heating failed, Printing Halted. Reset"

I disconnected the thermistor for nozzle 2 from the motherboard to take readings but as you would expect, once I set the heater 2 temperature ( to 100C ) I get the ERR MINTEMP message.

Can I put a volt meter across the heater 2 port to test for power or could this damage the motherboard?

The thermisters have to be unplugged before you can measure their resistance room temp 25C should be about 100K ohms.
What is the reading on your LCD for your hot-ends, if this temperature is below 15C the heater will never turn on. Unless you heat to above 15C.

You can measure the voltage however with a mintemp error the voltage will always be zero.
With the power turned off you should also be able to measure the resistance of the hot ends or bed, this should be between 1-20 ohms.

Edited 1 time(s). Last edit at 09/04/2017 12:08PM by Roberts_Clif.

I checked the thermistors with a meter and both were around 100K ohms. I checked them at the motherboard connector to be sure there was no break in the wiring.

The LCD reads 22C which is about right. It goes up slightly when the adjacent ( working ) hot end is on, as you would expect.

I just checked the hot ends and they both read around 5 ohms.

I don't know if this is a clue but when I set the temperature on the first nozzle, the fan on the power supply comes on while it is heating up.

When I set the temperature on the second nozzle, this doesn't happen, presumably because the motherboard is not drawing more power when it should be.

If it makes any difference, there is only 1 fan that I have mounted for both nozzles. I wonder if the system is not kicking in for the second nozzle because it doesn't find a fan?

I checked the voltage from the hot end power outputs, the first hot end reads around 24v while heating but the second power output reads 0v.