I have a similar issue with mine. Every once and a while it will trim up, but not down. To fix the issue, I always pull both relays and pop them back in. The relays are the two little black box looking things (about one inch square) on the side of the trim motor where the wires are connected (that is if your trim motor is like mine). They pop in and out like a plug in an electrical socket. With mine, the relays just get loose or the connections get a little dirty. If it continues to happen, I would replace the relays. I bought some backup relays from AutoZone that work and were pretty inexpensive. I keep them on the boat in case my normal routine fails.
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2001 Four Winns 180 Horizon
4.3L Volvo Penta
