Hey all,

I just purchased and installed one of those dash trays that replace the panel above the radio with one that is dished. When you swap over, you have to move the compass unit to the underside of the new cover.

Now when I set my cell phone/PDA in the tray, or my XM remote in one of the trays, the compass will read about 180 degrees off. If I remove them, it will re-set.

The manufacurer claims that it is not possible (code for probable) that the batteries in the items can do that. My question is, can this permanently affect the calibration of the compass?

Thanks for your input. Love the site!

 

You might very well alter it permnetly. Its unknown at this point. You cell phone has magnets in the speakers and this is probably the cause of your 180 degree deviation. As to say for certian it may be permenant? I an not sure. Chris

 

Mine does this too. The display for my compass actually went blank after about 30 minutes with my cell phone up there. I tried it a couple more times and had the same result. You could actually watch it swing around 180 degrees and then eventually shut off. The only way I could get it to come back up was to shut off the Jeep and restart it. Kind of upset about it because I bought it so I would have a place to put my cell phone. I can still make use of it though.

 

I have the dash tray and keep my cell there and have never had a problem

 

My compass goes wonky anytime my Blackberry get's up near that area on my dash ... freaked me out until I figured it out.

 

I have a Razor, never a problem with the compass when it in the tray... maybe it is dependant on the model of phone?
I lost a pair of sunglasses, slid across the dash, out the door.so, even with a gel pad, cell does not go up there anymore

 

maybe it would be possible to relocate the compass unit to somewhere else in the jeep.

 

This has nothing to do with the type of phone. I'm a ship captain and have to deal with this often.

This issue is caused by interference from metal in your phone being placed too close to the compass. The technical term for this is magnetic deviation.

Technical description: Deviation is the influence of the immediate environment upon your compass. Being a magnet, your compass will be attracted to (or repelled by) iron bearing metal and other magnets (including magnetic fields created by flowing electricity). Unlike variation, deviation is not constant, it's different in every situation, and it's even different within the same car, depending on which direction you're heading. Deviation is measured by the angular difference between the magnetic heading and the compass heading
** The fact that your phone is an RF emitter compounds the problem. (ie. It heartbeats with cell towers). Even if you powered your phone off you would still experience the issue most likely because the phone itself contains metal, some of it likely magnetized.

In fact, the reason the compass is mounted high in the plastic dash is most likely to get it away from any metal wiring & body parts to keep it as accurate as possible.

Simply put: When one mounts a compass it is best to keep it away from any metal deviation - as the compass works via it's attraction to the North Pole (Also known as 'Magnetic North'). Think of it as a line-of-sight issue in satellite communications.
For expample: If you have a wire physically running in front of the compass it will show a wrong direction if the heading you're Jeep is travelling puts the orientation of the wire between your compass and Magentic North.

As an expirement: If you have a handheld compass you can introduce Deviation by bringing a cellphone into it's proximity and watching the compass move.

One additional factor with the Jeeps' compass is it's computer controlled and probably averaging the bearings it recieves and using them to calculate an 'average' heading then displaying it ie. NW, SE, NE etc.
Once the deviation gets introduced by a cellphone sitting on the aftermarket shelf the deviation causes the compass to react outside parameters the computer can recognize thereby producing some of the wierdness you guys are reporting in this thread.

Now, Imagine getting a proper reading from a compass mounted on the bridge of a steel ship -There is actually a formulary I follow but it's based on eye readings that I take - not a computer processor like the JK's.

Hope that helps!

 

Wow!

You Da' MAN, dmos!

 

From what I understand if you leave your phone up there too long and the compass stays off by 180 degrees for more than 30 minutes, you risk throwing earth off its axis completely....therfore changing the current atmospheric conditions of the earths gravitational pull. In otherwords, Al Gore will be pissed....