Unfortunately, this part of the repair/upkeep process of my Brick is somewhat out of my hands at the moment, but I'd like to get advice anyway.

Last week, my tachometer began getting stuck at about 1,400 rpm. It would move appropriately fast as engine speed increased up to that point, but then it would lock into position, no matter how fast I revved the engine. Dropping below that speed would bring the needle back down.

Driving the car a few days later, I noticed the needle seemed to be sticking at a slightly higher point. When I ultimately took the car to a shop for other repairs, the tach was maxing out around 2.5K rpm.

My guess is that some kind of crud got in the tachometer itself, gumming it up a bit and blocking the needle from moving how it should. Slowly whatever it is was working itself free, but it wasn't gone completely when I handed the keys to the mechanic, so I told him to take a look at it. Probably all it needed was a good cleaning, but I figured the mechanic would be able to fix things more quickly than I could, and I'd already be paying him for working on the car for a few hours as it were.

I called today to check on the car. The mechanic said he had taken the tachometer apart and that he'd probably have to put in a new tachometer, with the implication being that he couldn't figure out what was wrong with this one. I told him to check on the prices for a used one, but that what I'd probably want to do is have him put the old tach back in and not worry about it (I can pull the cluster at some point in the future and clean things).

However, he said that if he put it back together I'd have to pay him (and I guess there isn't a guarantee it will work), so I told him to check on the cost of getting a used, working tach to put in its place. He said he'd do that and call me back.

What should I do? My expectation for the cost of a new tach would be about $50, a little under the cost for the time I would probably be charged for the tach to be put back together. Thus, a new tach seems to make economic sense, but I don't know how tough it will be for the mechanic to find one--most, if not all, of the junkers I've seen have had the big clock, not the tachometer. I would guess that getting a tach from the dealer would be exorbitantly expensive, too, and I don't think he'd be too eager to install one I found myself (though I don't see why not), either from eBay or a junkyard.

What do you think the mechanic means by "took the tachometer apart"? I know that it can be removed from the instrument panel, but beyond that, it didn't seem to be that easily disassembled when I replaced my odometer gear. I trust the guy not to do stupid, unnecessary things with the car, and I realize that some leeway is needed because the problem was so weird, but I'm beginning to get concerned that the mechanic is messing around with things that really aren't that important.
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'89 244 GL -- 106,XXX miles (see profile for info on car)