It seems my windshield washer has stopped working. While this is a common occurrence in the dead of winter if any moisture seeps into the nozzles or the fluid isn't potent enough, today it was sunny and not too far below freezing and I tried thawing the nozzles and hoses with a heat gun, but no luck. I can disconnect the hose at the filter near the firewall and suck and blow in it and there appears to be no obstruction, but no fluid comes out when I work the washer. Yes, I topped up the fluid.

I had noticed when it was working that the streams were kind of weak. Could the pump be at fault? Where is it located? Is there a fuse?
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1992 745, >500k km