Representatives from Opel's 4,000 dealers in Europe are expected to vote in favor of taking a direct equity stake in the ailing German carmaker when they meet in Vienna on Friday.

The umbrella association Euroda wants all of its dealers to contribute 150 euros from every sold car over the next three years into a joint fund that could raise as much as 500 million euros in fresh equity.

Together with Opel's 50,000 European workers, they would like to hold a blocking minority in any new Opel company.

Aachen-based dealer Esko Thuellen told Reuters ahead of the meeting that there had been some amount of controversy regarding the plan since the money constitutes a burden on dealers who often earn very thin margins.

This is my personal opinion, but if there is some sort of investor model where the dealers don't have to contribute or only need to do so to a smaller extent, I don't think that they would be nonplussed, he said.

Since virtually all of Euroda's national associations have already approved the plan individually with the exception of Finland, the vote is more of a formal affair.

The discussion will then move on to the details of how payments will be made should any eventual Opel investor welcome their investment.

Thomas Bieling, one of the two co-chairmen of German Opel dealers' organization VDOH, has voiced skepticism regarding Fiat's interest due in part to years of confrontational stance between the Italian carmaker and its German dealers.

(Reporting by Christiaan Hetzner and Angelika Gruber; Editing by David Cowell)