Wrong with the gas furnace

Note: the below was solved. It was a loose wire between the controller and the gas valve (the white wire on the diagram)

This is about an old UltraMax Olsen HCS2 81AD gas furnace

it looks like this

and it sounds like this 🙂 when it is having problems

Here is what happened this morning. I waked up hearing the a noise that was coming from the furnace. I wend downstairs to the furnace room and it was making a sound like this (click to download a small mp3).
I switched the furnace off and I went upstairs to get my phone to take pictures and record the sound. When I returned I tried to start the furnace one more time and it started. It worked for a little while and it stopped again making the same sound
I switched the furnace off again and went upstairs to read a little bit about it (we bought the house this summer and I don't know much about it) and when I returned I started the furnace again. I think it worked again till it reached the temperature set on the thermostat and it stopped again making the same sound.

I am now waiting for it "to rest" 🙂 and I will start it again but with an increased temperature. It was set to 21.5 before, now it is set to 23 ..I want to see what it is going to do this time

Now the questions for you guys:
-can you say by the little info provided here what is going on?
-can anybody tell me what would be the cost to replace the furnace (I live in Toronto) and if it is worth replacing it? I would be curious to hear what are the main advantages that the newer models have over this ancient model (1988)

Y9u can listen to the sound it makes online here