Hello electrical masters
When I turn off my bathroom fan , the portable 1800W heater in my room connected to the bathroom shuts off sometimes [trips the gfci button to off] .This has a GFCI on the plug not the outlet . Are these on the same circut . Any idea what can cause this? Do i have an overloaded circut? And why would that outlet be on the same circut as the bathroom fan switch. Also I notice the bedroom light flickers sometimes.This all just started doing these things after i put a portable heater in this room.
Thanks all
Sounds like your heater is your problem. You should have an electrician in to check out the circuit and panel.
I second the first reply–get an electrician to check it out!! Space heaters are a very common cause of house fires because they draw so much power.
If there are any loose connections, the substancial current draw from a space heater can cause them to overheat. Flickering or especially dimming of lights under load can be a sign of this and in this case there is certianly enough to warrant calling an electrician.
Most likely the flickering of the light is caused when the space heater turns on and off during operation. What you don’t want is bad connections somewhere on the circuit that the space heater is plugged into heating up enough to cause a fire.
Many people believe that a certain dimming of lights when using high power appliances is normal. In my experience when the connections are tight, this is not the case at all.
Get it checked by a professional before something happens.
Joey and Raymond gave you good advice Rafael. I hope you heed it. 
Have the electrician check out voltage drops. This is, most times, an indication of a loose connection some where.
With a loose connection, the connection is not physically tight and causes resistance. Where there is resistance, there is heat. Where there is heat there is more resiistance and the added heat can cause a fire from the hot connection. If the lights actually flicker, instead of just dimming, it could mean a connection so loose that it is arcing. Much more serious.
Get it checked out, please! Hate to see you and yours hurt.
Hey thanks you guys . did i mention the gfci button trips to off position when i turn the fan switch on or off. Does this change anything? will have it checked out. Thanks again.
Rafael
If the electrician checks it out and says the problem is the heater make sure you have another heater to test with to be sure. You could have more than one problem that could require some advanced troubleshooting.
As to GFCI the plug could be defective, miswired, the heater draw is to great or its an old GFCI, they do fail over time.
Thanks everbody , i appreciate it
Can we invoice you? 
Just kidding. Glad we could help!