My 63 LeSabre has what I'm assuming is a block heater. There is an AC cord that plugs into a port on the lower passengers side of the block, near the oil filter. I've never used it. Did these come installed from the factory, or did one of the previous owners install this at some point?
Actually, I think that up north those were available from Buick.... nice to have... if you rig it up right, they will unplug themselves as you back out...
Most Canadian built Buicks had them in them; - they were listed as a dealer installed item, (an added extra cost on the invoice) but they pretty much were standard equipment. The thing to watch out for is a frayed cord, and leaks around the heater itself. I've seem people "zap" themselves pretty good when plugging them in, because the cord was stretched when they had previously pulled away and forgot to unplug it. Some people would install block heaters whenever they had a leaky frost plug. They only last a few years before they start to leak, so when you rebuild the block, get rid of it.
