The switch reduces the impact of the ASR system to 30% of normal (but as deanyel says, doesn't completely defeat it). As he says, it's intended to help get you unstuck if you have tire chains, but I've used it many times with dedicated winter tires without chains, too.

Personally, I wouldn't be without ASR (since I need to drive in snow this time of year). The 400E/500E produces enough torque that you get a lot of spin if you encounter slippery roads.

I'd also suggest you call 1-800-FOR MERC and order an owner's manual.

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Steve
'93 400E