Lopsided heater!!

Yes I know, another bloody heater question. And `search` doesn`t tackle this, that I could find.
When starting journey today, I couldnt hear the heater blower, nothing coming from vent my side, so assumed maybe check the fuse when I get back.
Asked the wife to feel for air coming out vent on passenger side and lo, there was warm air softly coming out. Still nothing my side. Still cant hear blower.
Is the fact I`m getting some air out, an indication that the heater is working but maybe clogged up, or could the warm air passenger side be engine heat finding its way thru?
My heating system does need a bloody good overhaul to be fair, hasn`t been good since I got it, and previous owner used to wade every w/e I think judging by the dried mud I found EVERYWHERE. So matrix prob has more mud than air in it.

Think you will find yer fan isnae working and as you drive along the air is being pushed through into passenger side only as thats where the air comes in. If yer lucky you wont have to replace your heater motor but if you do there are loads of threads about it

Could be you have what I had, the pipes in the dash can fall and drop off inside the dash. Have a look first!

mine does this every now n then try bang the heater box under the bonnet with ure hand and c if it makes any differnece, mine does.

All good stuff, thanx guys.

Bought a bunch of fuses as when I checked them the heater blower one had fused, plus some others were missing and no spares either. So, fuse stock sorted.
However, when I replaced the heater one(15a), It sparked ,( made me fu**in` jump), and fused immediately. What do I do now?
Unscrew the plate the fuse box is on and pull all that `spaghetti` out ??? Am I looking for something as obvious as a loose connector or will it go deeper than that?

Fuse for the heater blower was gone, put a new one in, it sparked like a good `un and immediately blew.
Obviously a live wire, so what could be the cause? S`pose I know the answer.
Have I really got to pull all the wires out and check them all?