Has anyone else here ever checked the calibration of their mirror-compass?

When I bought my car, a 1-owner California car, the mirror was still set to Detroit's
longitude 8 years after it was first sold! So much for "dealer prep"...

Yes, I was Anal enough to read my owner's manual after buying the car and the PO had it set to Detroit longitude still.
having worked at a dealership for a while and reading the new Car Prep Checklist, Setting the Compass was not on any prep sheet.
So the mechanic's responsible would not know to do it and boneheads like me that were responsible reviewing said checklist's didn't have a clue either.

Not only do you have to set the 'variation' depending on where you live, but if you want it to be accurate you also need to put it into 'calibration' mode and drive around in some slow consistent circles. One of the first things I did when I got my Riv.

(I calibrate marine compasses for a side-living)

I calibrated mine once, but didn't notice much difference. Since that time, I've drained my battery completely a couple times, and disconnected the mirror for a week, and it still reads perfect.

Quote:

The problem then is that visual cues (the direction of shadows for instance) then sometimes don't match what the compass is telling me. I guess you could say it's noticeable but not *that* big a deal once your remember what's going on.

I've noticed this as well, but I don't think the compass is wrong. The sun doesn't always project accurate shadows, because throughout the year it moves on different paths across the sky. It also varies depending on N/S location:

good points Aaron...

Except, in the Northern Hemisphere (where we are) doesn't the sun's apparent arc run southerly? In your drawing it runs northerly.

If so the angles in your drawing are about right for the seasons in North America but the compass headings should be flipped N/S. Looks like your drawing was done for maybe Chile or Australia. Or southern Africa...

That is, the reason the equatorial regions are tropical is they get more hours of and more consistent sun. Sun shines, in general, on the southern exposures of buildings in the northern hemisphere, and on the northern exposures of buildings in the southern hemisphere... your drawing shows sun on northern exposures.

Comments?

Albertj

Yes, the shadow angles should be reversed, but the diagram would be correct for someone in the southern hemisphere. Either way, you won't get a perfect overhead path of the sun unless you live somewhere ~12º north or south latitude, like in northern parts of Australia. There the shadows would point almost directly east or west for much of the year.

I just purchased one that was out of a 99+ Intrigue. It's supposed to be a plug and play unit. The map lights and auto dim work perfectly fine but... The compass only reads NW most of the time. Sometimes it will switch to W or N. I know it's wrong because I was driving on I-91 S and it read NW.

Is this just a bad unit or is there a way to calibrate it?

I got this..

Let me know if you need help. I ran mine through the calibration (it's in the owners manual) and not that it matters but I also calibrate boat compasses on the side.

When i wired up one of those to work in my 96 i had to calibrate it.
manula says to drive in a slow (<5mph) tight circle 2-3 times to calibrate the compass.

Mine is from an Olds Alero and it has extra lights on the bottom that point perfectly in the laps of the driver/passenger.
defiantly worth the afternoon of running a few wires around.

Mine might be bad which is odd... To reset, I had to hold down both map lights. After 10 seconds, the screen changes and displays an "8". That stays for another 10 seconds. I tried the driving in circles going slowly as described here. Did it twice and it didn't change. The mirror almost constantly reads "NW". What really worries me is that this compass only reads "NW" and "N". WTF? Guess the compass unit itself is ruined or something.. I might have to alert the seller to this and hope they are good with customer service.