How to check if junkyard odometer works?

[E30 Wagen]

Is there a simple way to check if the odometer gears on the cluster work without taking it all apart? There's a M42 engine/tranny in a cabrio that I want to get and the odometer indicates around 165k. That's way less miles than the tired, oil leaking M42 I currently have but I want to verify if that mileage is accurate before pulling the trigger.

[george graves]

No, BMW ended the machanical ODO's with the e21. E30's have a "speed sensor" on the diff, that drives a motor inside the cluster. Best guess would be a VIN and a car fax to look for that. Even then, it's a crap shoot.

[Gregs///M]

Even if the odometer gears are good, the electronics commonly fail. We see it many times per week.

[squidmaster]

You could simulate the input with a signal generator. You would need a 12v source as well.

Realistically, the chances of finding a working odometer in a junkyard is.... well, less than me turning into Idris Elba. It'd be quite a hunt.

[george graves]

Even if the odometer gears are good, the electronics commonly fail. We see it many times per week.

Diff sensor you mean? Just curious.

[M-technik-3]

Pay 20 bucks for cluster and and try in your car is easiest method.

[e30sh]

If trip odo reads all 0's, odds are it's broken.

Look at the seat / steering wheel for wear. That's good for +/- 100k lol

Do the easy first...check the plugs. If they look ok, pull the valve cover and check for pointy cam sprockets / sludge etc.

Most yards off some type of warranty.

[M-technik-3]

Electronic is a toss in the dumpster. Way I look at it if it has a nice bezel than it's worth 20 bucks and the rest is scrap. I can't tell you how many cars over the decade have had scratched plastic lense.

[Gregs///M]

Diff sensor you mean? Just curious.

No the PCB behind the speedometer.

If trip odo reads all 0's, odds are it's broken.

Look at the seat / steering wheel for wear. That's good for +/- 100k lol

Do the easy first...check the plugs. If they look ok, pull the valve cover and check for pointy cam sprockets / sludge etc.

Most yards off some type of warranty.

The trip can read zero whether or not the odometer is good or bad. Someone could have just reset the trip, has nothing to do with good or bad gears.

[e30sh]

The trip can read zero whether or not the odometer is good or bad. Someone could have just reset the trip, has nothing to do with good or bad gears.

You are correct about it reading zero good or bad.

My point. What are the odds of it ready exactly 0 if it was working? I've seen a lot of e30's with broken odo gears and most have trip odo's at all 0. I assume people push the reset button after it stops thinking that will magically make it start working again.