LulzBot 4 E1 Heating Failed Error after firmware upgrade

I have not ben able to print from a Lulzbot 4 after a firmware upgrade. At first, I wasn’t able to print from the curalulzbot app, but it was able to print from the SD card input. The bed and printer head were able to heat up and extrude plastic and print like normal. Since the printer would not connect to the curaluzbot application, I upgraded the firmware through the application to lulzbot 5. It completed successfully and I was able to connect to the app and send commands to move the printer. However, after the firmware upgrade, the printer was no longer able to heat up the nozzle. Anytime I print from computer/sd card or preheat from computer or the built in display the printer just doesn’t heat up the nozzle and eventually spits out the following error: E1 Heating failed, PRINTER HALTED. Please reset.
The nozzle is cold to the touch and touching it with my hand warms it and the temperature shows it heat up a degree or two. I have tried changing the firmware to lulzbot 4, but it didn’t help. The weird thing is that the printer always boots and now says luzbot 5 regardless of whether I have put on lulzbot 4 or 5 firmware. Before the firmware change, the printer would boot up and say Lulzbot, but wouldn’t specify a number. However, the Marlin firmware number does change and the ui looks a bit different as well. Regardless, the nozzle will not heat up. When on firmware 5, I able to send commands to move the printer head or send it to the home position and preheat the bed, but not able to preheat the nozzle as it when I click, nothing happens and it eventually spits back the E1 error again.
What could be causing this since it was working fine and able to heat the print nozzle before I upgraded through the app to lulzbot 5? I’ve seen others have this error when their hardware failed, but all I did was change the firmware and it stopped working immediately afterwards. What should I do from here?

Did you just dig this thing out of storage (or get it donated to you), or have you been using it right up to the firmware upgrade and subsequent failure?

Since it registers the heat change from your fingers, it’s doubtful it’s a firmware problem, as wiring between the 4 and 5 is the same.

Get a multimeter and verify that there’s voltage going to the heater. There’s a chance your extruder power solder joints gave out, or the power harness for it got melted.

It was given to me by a friend and I wanted to use it to print a case. I don’t have a multimeter right now, but once i do get one, where exactly should should i put the two ends to check for both those problems?

Is it still the original toolhead that looks like this?

Then you’re really using some obsolete tech, and honestly, the work to get it printing anything besides 2.85mm ABS filament is going to be a bad investment in time and money.

Assuming you are using the taz4’s default extruder, you should be able to put your multimeter leads to the red wires through the pin “windows” on the other side of this harness:


If there’s 24v there when it is attempting to heat, the heater is no good. The heater for the taz 4’s Budaschnozzle 2.0c hot end is a 4.7k ohm resistor

If there is no voltage there, check the other side that the identified plug connects to, and finally you’d check at the actual control board.

If your friend did some upgrades to the toolhead, it may be this (taz 5 toolhead)

Or the taz 6 toolhead:

If it doesn’t look like any of these, check this list and report what it is: