Guy's I have a 1984 244GL 266K and a 1992 245 115K.
The number 10 fuse on both cars have all of a sudden
started to blow out. The #10 fuse controls the power
windows. Any idea what could be the cause of this ?
Any help would be greatly appreciated.

The same fuse that goes to your windows also goes to the optional a/c fan, if that has been installed. What happens is that you are opening or closing one or more windows at the same time the a/c delay kicks in, so between the a/c, the fan, and the windows, the circuit gets too loaded for the fuse. I had the same problem with mine. According to my mechanic, Volvo issued a field bulletin for this which said to upsize the 8 amp fuse to 16 amp. That's what I did, and that solved my problem. Ordinarily, I would never make this kind of change, so do so at your own risk, assuming your problem is the same as mine, and it sounds like it is. I have not seen the actual bulletin, but my mechanic has been doing Volvos for 30 years, and generally knows his stuff.

Interesting that you have a similar problem as mine. Big problem though.....my passenger window is down and we are expecting rain. Heidi is a 91 240 DL 137K. At the same time the button on the top of the shifter will not operate, I had to manually unlock the shifter to go into reverse. This all happened in an instant when my wife was at the store. The #10 fuse is not blown. Any ideas on what the problem might be?

Just a note to reply to readers and myself......I went out and cleaned the #10 and #7 fuse and receptacles and the problem went away. Simple fix. Sometimes my cars humble me so.

bad wires that causes a short to the ground

or the power windows are internally fried up, but I hardly can believe this because it is a simple robust VDO/BOSCH motor.

other possibility is the switch that causes shorts

first look for continuities to the ground in the live wire: this may not be the case, if so this causes shorts and blowing the fuse
test the circuit with a amp meter
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240 '88 B200K 260kkm virgo+all gauges,Phoenix Gold ampli, Focal door speakers, debadged, 6 rear red lights