[Solved] RAMPS heater not heating up

Hi,

I'm building my first RepRap and there is a problem with the heaters, I have searched for answer but not found anything that could solve my problem exactly.

I have RAMPS 1.4 with Sprinter and I have pronterface to connect to the printer. The motors are working great, I get a readout on the thermistor after a lot of headache but the heaters are not heating up.

I have two 6.8 Ohm heating resistors that I have verified and they do heat up if connected straight to a 12V supply but they do not heat up when I ask pronterface to set temperature, what I get from pronterface is: T:25 @:0 B:25. If I put a multimeter there are 0V over the terminals and 3.4 Ohm (which makes sense since the heaters are connected in series). (I do not have a thermistor for heated bed since I don't have a heated bed fitted on my printer at this time if that's any help).

My power supply is 12V and supply 40A, that should not be the problem.

Any suggestions of what I might be doing wrong?

Any help will be appreciated. Thanks,
Gisli Steinn

Edited 1 time(s). Last edit at 04/10/2012 07:13PM by Gislinn.

Ok I have some progress and I'm just going to put it here if anyone else is having a similar problem.

If I set the temperature it outputs for a second and then stops but if I keep my multimeter on the terminals while I set the temperature it keeps heating (even if I remove the multimeter). So I can make it start by keeping the multimeter on the terminals for around 3 seconds and than it runs fine and heat up.

I think it's a really strange and I have no idea what is going on. Any input would be great.

EDIT: Ok scratch that, It's working perfectly now after a restart, powering of the arduino and I cannot recreate the not heating up thingy. So I'm a happy puppy now.

Edited 1 time(s). Last edit at 04/10/2012 07:13PM by Gislinn.