The chief financial officer for Vestas Wind Systems has stepped down after nine months on the job, dealing the troubled Danish wind-turbine maker another blow as it works to reverse a string of deep losses and build relationships with investors.

Dag Gunnar Andresen, who became CFO last summer following the abrupt departure of his predecessor, will leave Vestas at the end of the month. He will be replaced by Marika Fredriksson, a Swede with an extensive financial background who is an outsider to the renewable-energy industry.

Mr. Andresen cited personal reasons for his departure. He leaves as the wider industry for wind turbines remains under pressure because of rising competition from companies in emerging markets and a lack of wind-energy subsidies.

For Vestas, the latest management move represents another turn in the turbulence engulfing Vestas' upper ranks. Early in 2012, the then-chairman and his deputy stepped down following the firing of Henrik Norremark, who had been the finance chief and chief operating officer under Chief Executive Ditlev Engel.

The company let Mr. Norremark go after two profit warnings sent share prices tumbling.

Mr. Andresen later joined the company and helped oversee a restructuring plan, bolster relations with banks and other investors and shore up the balance sheet in the second half of 2012.

Shares fell 2.2% during trading Monday. The CFO's departure was announced before the market opened.

Shares have recovered since touching historic lows last year, but they are still 90% lower than the highs set when the company was winning new business and a darling of the renewable-energy sector in 2008. The recovery can, in part, be credited to Mr. Andresen.

"There is no doubt that Dag Andresen has been one of the driving forces behind the turnaround," Klaus Kehl, analyst at Danish financial services group Nykredit, said Monday. "He was also good [at] communicating."

Vestas has recently been shedding jobs and moving away from unprofitable business lines, but there remains uncertainty over whether it will be able to seal the strategic pact with Mitsubishi Heavy Industries Ltd. that has been under discussion since August. Investors applauded the potential tie-up when it was announced, sending shares significantly higher amid optimism that a deal could secure Vestas' long-term future.

Ms. Fredriksson takes the finance job May 1 and will be confronted with the challenge of keeping the company viable. Vestas posted a net loss of 963 million euros ($1.26 billion) in 2012, and free cash flow was negative EUR359 million.

Management has in recent weeks indicated that its difficulties are subsiding. Last month, at the annual meeting, Chairman Bert Nordberg said "Vestas is a stronger, more realistic and cautious company than it was one year ago," with lower fixed costs.

Ms. Fredriksson previously served as chief financial officer for medical-technology company Gambro, automotive-safety systems manufacturer Autoliv Inc. and construction-equipment manufacturer Volvo AB. Michael Jorgensen, an analyst at Danish financial insurance group Alm Brand, said that her profile makes her a good fit for the company but she will have to build up trust with investors.

She "has to take over in the middle of a restructuring phase without having time to get to know the company under calm circumstances," Mr. Jorgensen said, adding that this may "delay" Vestas' attempt to attract new capital.