Fiat Doblo 2006 1.4B - Blows the fuse for the blower and reverse lights

Patient Fiat Doblo 1.4 B + LPG MAXI CARGO 2006

I have a problem. The fuse F31 in the box under the steering wheel blows, which results in blowing and rear lights
while driving I have a non-stop blower in 2nd gear and I do not move it after replacing the fuse, everything works non-stop for about 1.5h and then the fuse blows.

The blower works without major resistance on the engine, the car has no air conditioning.
Everything seems to be playing and the fuse is falling. Do you have any ideas?
Newspaper in this car, so the engine works non-stop for 5-6 hours at night.

Replace the relay with B01.

Thanks a lot for the answer, the relay change meant that today the fuse did not burn 5h of fan operation and nothing happened
The relay cost PLN 25 ...

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