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Posted: 5/9/2026 7:35:26 PM EDT
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A long time ago I once had a dashboard mounted compass that worked very well. But now I see warnings that dash mounted compasses don't work well because of all the steel in vehicles interfering with the earth's magnetic field inside the vehicle. That is hard to believe because vehicles now have less steel than ever before. I wonder if the problem might be the electronics in the newer vehicles generating interfering magnetic fields. Any ideas about this issue? Has anyone used a dashboard mounted compass to navigate remote trails? I would guess that a GPS based compass might be immune to the magnetism problem. |
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Magnetic compasses on steel vehicles is a solved problem. Every steel oceangoing ship has a magnetic compass and the influence of the steel hull is minimized with a calibration process and a set of iron masses on the binnacle There are car compasses that incorporate a similar device. I had one in my old truck. My new truck has an electronic compass. Electronic compasses include a calibration procedure to minimize the effects of the steel body. |
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Originally Posted By Ndenway1twicetimes: Everyone had a pedistal compass ball mounted on dashboard when I was a kid, Hell when got my first vehicle in the 80's had one. Nowadays got one in the bob with a state map jic, but use the gps on my phone. |
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It appears that there are two types of compasses for vehicles, a GPS compass that determines directions using GPS signals and a magnetic compass that responds to the earth's magnetic field. A GPS compass is not affected by interference from iron or electronics or motors common in motor vehicles, but a GPS compass must be moving in order to display directions. So a GPS compass doesn't work if you are not moving. A magnetic compass is subject to interference by nearby iron as well as radios, electronic Instruments, electric motors, stereo speakers and windshield wiper motors. However, nearby iron, such as in the dashboard and body of a vehicle, can be compensated for by good compasses that have calibration adjustments and come with calibration instructions. But some modern vehicles have a large amount of wiring, radios, electronic Instruments, electric motors, stereo speakers and windshield wiper motors near the dashboard that generate fluctuating magnetic fields that may not be able to be corrected, so manufacturers sometimes recommend that the compass be located high up at the top of a windshield to try to get away from the above mentioned electrical and magnetic interference. So, whether a magnetic compass will work depends on how much electronics your vehicle has under the dashboard. Many old trucks are fairly simple, hence the stories of old trucks with compasses on the dashboard. Do an internet search for "automotive compass" to see what compasses are available. |
There's a handful of Chicom ones on Amazon. For $6, I picked this one up. 
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Originally Posted By AndBen: There's a handful of Chicom ones on Amazon. For $6, I picked this one up. www.amazon.com/dp/B0DF7KLJ7T So, did you install it and did it give accurate directions? |
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Originally Posted By DonSaba: So, did you install it and did it give accurate directions? Originally Posted By DonSaba: Originally Posted By AndBen: There's a handful of Chicom ones on Amazon. For $6, I picked this one up. www.amazon.com/dp/B0DF7KLJ7T So, did you install it and did it give accurate directions? I just order it tonight. Ill have to report back. |
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Attached File I ran it against my inboard truck compass and my iPhone compass. Not sure of the science behind it, but the only direction is was accurate at was when heading SE. Otherwise, it was very inaccurate at best…sometimes off by 50-180 degrees. |
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Originally Posted By Bladeswitcher: Dashboard mount for cell phone? Turn on compass app? Onboard navigation/gps program? I’m confused. Are you restating what I did, or offering ideas to a problem I’m not trying to solve? |
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Originally Posted By AndBen: https://www.ar15.com/media/mediaFiles/481934/IMG_0948_jpeg-3762594.JPG I ran it against my inboard truck compass and my iPhone compass. Not sure of the science behind it, but the only direction is was accurate at was when heading SE. Otherwise, it was very inaccurate at best…sometimes off by 50-180 degrees. @AndBen If it is magnetic you could try placing the compass up high where the rear view mirror is. Placing it up there might get it away from all the electronics and magnetism under the dashboard. |
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Originally Posted By Spydermonkey: Thats a memory unlocked from the 80's. My grandpa had a bubble ball compass mounted on top center of his dash in every truck he had. I remember those!  Haven’t seen one in forever though. |
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I posted the same question months ago. Still haven’t found one I like. I found a new inbox compass that looked awesome. It’s probably 30 years old and in perfect condition. Very high quality and it has the option to wire it for illumination. Problem is I didn’t look up the size. Just guessed. It’s freaking huge. Ok, 4” across but it seems big on the dash.  Glad I passed on the Amazon compass. Attached File |
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Some cars/trucks have optional rearview (R/V) mirrors which can include a compass and other things, like auto dimming and a garage door opener. My 2005 Subaru Forester was pre-wired for the R/V mirror, and $5 salvage yard R/V mirror was a 5-minute install. Found calibration instructions on the web. An excellent mod, and the compass is more useful than one would think. Auto dimming feature is appreciated every night. Never used the programmable "HomeLink" garage door opener feature. The "trick" here is to search and find out if such an R/V mirror was/is available for your particular vehicle. Search using "auto dimming rear view mirror" and see what happens. If you're lucky, your vehicle is pre-wired, and install is simple. Other than that, the stand-alone auto/marine compasses should be illuminated, and mounted in a spot which prevents them from being a hazard in a collision. These compasses must have calibration adjustments. |