How does my Compass know ?

[MarineBSP]

I have noticed lately that the compass reading in my EVIC is erratic. Sometimes it is as accurate as a person could hope, and other times - on the same drive - it will be 180 degrees wrong. When it is wrong it does change left-right-left keeping the error consistent.

I'm not terribly bothered, but it really has made me curious - How does my compass get its bearings ? GPS ? (I don't have Nav), Magnetic North ? (unlikely), piggy-back off cell phone ? (my iPhone is usually NOT connected by wire).

Anyone with inside knowledge care to share ?

 

[misfit77]

Satellites detect direction from change in position and speed from its rate in change. Then sends that info to the head unit.

Is your speed accurate?

My guess is the head unit is at fault. Maybe a loose antenna connection.

 

[MarineBSP]

So it's primarily vehicle GPS via Uconnect ? Do you know if there's any cellular connectivity component ?

I ask because where I live the cellular connections are notoriously bad, so if the satellite data was used only periodically, and cell tower signals were used in between, then it would make perfect sense that it would go goofy once in a while and the next time it checked in with the satellite it would correct itself.

I have no other indications of anything wrong - speed is accurate as nearly as I can gauge from roadside radar signs, mileposts, and surrounding traffic.

 

[misfit77]

Crap.,forgot, car gps typically don't display speed. Sorry about that.

 

[crash68]

How does my compass get its bearings ?
Anyone with inside knowledge care to share ?

There is a compass module that is part of the HomeLink buttons in the overhead.
part# 68105821AB
You could try calibrating the compass:
https://www.mopar.com/en-us/care/dy...D45463CE-C042-448A-85DD-DB87E9AA3DD8&tocID=50

 

[canadiankodiak700]

If you have a compass, then you have a compass module up in the roof. If it's occasionally going wacky, it needs to be calibrated. This is done by litterly driving around in a parking lot or large open area away from large metal buildings, in a figure 8 pattern. 4 or 5 complete figure 8 will calibrate the modual.

Sent from my Pixel 5 using Tapatalk

 

[Murphy Slaw]

If it's occasionally going wacky, it needs to be calibrated. This is done by litterly driving around in a parking lot

I did mine right before Christmas.........

 

[MarineBSP]

Thanks guys - calibrating later today !

 

[Docwagon1776]

Magnetic north, and if you have a magnet too close to the module you can have issues.

See:

Keep magnetic materials away from the top of the instrument panel, such as iPod's, Mobile Phones, Laptops and Radar Detectors. This is where the compass module is located, and it can cause interference with the compass sensor, and it may give false readings.

(note this is a generic warning from FCA, I don't know where the sensor is in our RAMs.)