Blown engine fuse after AC is on for 30 minutes

I've got a 2001 Ford Focus SE Wagon (Zetec), and after having the AC on for 30 minutes, going with moderate speeds (around 2k RPM),
the fuse for the engine (20AMP) will blow.

This happens to me consistently - if I have the AC on for more than 20 minutes.. the fuse blows...

Without AC there are no such problems..

I recently changed timing belt + water pump + driving belt, but don't think that would be related..

Any ideas much appreciated

I'm looking at the diagram, and there are 3 relays connected to that fuse.
It's something like that:

HOT AT ALL TIMES --> -- fuse 20AMP --->---- (goes through a power hold relay, which is turned on when the ignition is on) -----------> splits into 3:

1---> Engine Cooling Fan Relay -----> PCM ground ( I guess PCM controls this, whether it's on/off)
2---> High Speed Engine Cooling Fan Relay ----> PCM ground (different wire from above)
3---> A/C Wide open Throttle (WOT) relay ---> PCM ground (different wire from above)

So, I guess, when the PCM decides to activate one of those 3 relays, the fuse blows.

The fuse has never blown so far when the AC wasn't on (although it hasn't been too hot outside yet, like more than 25C, I'm in Canada )

I suspect the High Speed engine cooling Fan relay, what do you think?

I went to the dealer, and they, playing stupid, said that the fuse was connected to a few places (c'mon it's only 3 relays), so they didn't know which one it was.. They charged me $200 to clean up the grounds and temporarily install a circuit breaker.. This didn't help though. - after 20 mins of slow driving w/ AC, the circuit breaker blew, I pulled over, after 30 seconds, it started back on, and with the AC still on, it blew back again in like 30 seconds..
I waited like 2 mins, turned off the AC and continued on the highway.. after a few minutes - bam, same problem.. pulled over, waited like a minute and continued - after 2-3 minutes - again.

So, do you think it's a connection problem or a faulty relay or something else?

One more thing - my heat shield (the one on the manifold, between the the manifold and the fans/radiator) has been removed..

It turned out.. that the m*** f*** "High Speed Engine Cooling Fan Relay" was not original Ford, but a Bosch one.. And it actually had different specs.. not just different specs, but completely different wiring..hahah

i.e. the 20amp fuse wire was supposed to just control the relay (on/off), but instead it was being fed into driving the FAN..

The fan was supposed to be driven by wire with 50 AMP fuse.., but instead this wire was driving the relay......

gee, I wonder why a mechanic would put the wrong relay, without even looking whether the diagram on the relay matches on what's expected..
it was all on the relay, written very clearly, which wire does what...

cross your finger I'm right.. we'll see on Monday if this works out...