Help, Rear Defogger shuts off Fuel Pump

[sm2by]

I just got my Yaris from the Dealer after a warranty replacement on the oxygen sensor, my car had rough idling so the sensor was to blame. After 4 days, while getting ready to drive out my Yaris sputtered and stalled, I tried to restart but it just choked and stalled again, then I turned off the lights, radio and Defogger. It suddenly came back to life, but when I switched on the Defogger it started to die again.

I brought it to a local shop, they said the Fuel Pump is not getting any power when the Defogger is on, they also said a relay was clicking when the Defogger was switching on so maybe a faulty relay? Planning to take my Yaris back to the dealer for some serious Questions and if necessary Accusations....