possible cure for x50 false laser alerts

[armscrafter1]

I visited this forum a while back and got some ideas here about what might be causing false laser alerts on my 8500 x50. I drive a Subaru STi. I've had great luck with my 8500, but sometimes it gets into a string of false laser alerts coinciding with hard acceleration.

One poster's theory was voltage spikes. I switched my unit to V mode and found my voltage to be over 14 volts probably 75% of the time. The voltage doesn't really fluctuate much. I decided to go with another theory that it was caused by stray RF in the car's circuitry. Here's my fix:

I use the smart cord, which plugs into the unit with the RJ11 phone jack. I obtained the following from Radio Shack for about 6 bucks: 1 6" 4-conductor phone cord w/ male RJ11 on each end (I call this a patch cord because it's so short). 1 female/female RJ11 coupler. Then from an old computer monitor clip the RF filter thingy out of the power cord. It's the component near one end or the other of the cord about the size of a small battery. Leave a couple inches of wire to work with.

Take the 6" patch cord and slit the sheath open in the middle for about 3 or 4 inches. Take out the green and red wires and cut them in the middle. Bare the wires on the patch cord and the RF filter. NOTE: on my smart cord, the wire colors were exactly the opposite of the phone cord, so I connected the + lead on the filter to the green wires on the patch cord, because + on the detector/smart cord is the red. This keeps it correct all the way through, even though the + is now green on your patch cord. So anyway, be sure to attach the + and "-" to the correct wires in the patch cord. Connect everything so it's road-worthy using electronic solder. Insulate with tape or whatever. Attach the f/f RJ11 coupler on the end. Secure the whole thing with some electrical tape and dress it up so it looks nice.

Now you can plug the smart cord into your new filter assembly and plug the filter assembly into the detector. This way, you can use it or not, or use it with other units, and you don't have to destroy a smart cord to do it.

I have spent considerable time trying to get a false laser alert after installing this thing. Nothing yet, and all else seems to function fine. I can't be sure it has actually done the job, only that I haven't had a false alert since installing it. Just to try to be somewhat scientific about it, I did leave it off the unit at first until I got my first false alert, then clicked it in while driving, and then got no more false alerts. Anyway, it's so cheap, if it doesn't work for you, you can throw this thing away and not feel too bad about it, then spend the 80 bucks with Escort to get the falsies fixed. Since you haven't changed anything on the unit, no one will know you've been experimenting. Another Note: I'm not an electronics guy, so do this at your own risk (though I don't think it's very risky).

Incidently, I used to test my laser detection by shooting the detector with a laser rangefinder (like those used for hunting/shooting). It sets it off just fine. I haven't done this yet this time because the range finder is dead right now. It's a good way to test it though, I think it's basically the same technology.

[kpatz]

Can you post a pic of the RF filter thingy you used?

I'm curious whether it's a choke, capacitor, or just one of those ferrite beads you wind the cord around.

A friend of mine has an 8500 with the same problem, and next time we get together we want to try a fix.

[TSi+WRX]

Very, very interesting report, armscrafter1!

Thanks for the heads up - but yes, more details, please.

There's a fellow Subaru driver on the LegacyGT.com Forums who is having similar problems, and I'm wondering if your setup might be of help to him, too.

Out of curiosity, which Revision is your x50?

Both mine and my fellow Legacy driver's are Rev5 ( his is un-verified, but from its date of purchase, I'd say that I'm willing to place a dollar-bet on that ).

In my two Scoobys (both '05), I also always see >14 volts during vehicle operation. When I used to run my x50 in that mode, I always saw between about 14.3 and 14.5 volts - I currently have an analog AutoMeter SportComp II voltmeter gauge and have thus stopped using the x50 for this purpose, but I see about the same.

I've never had my x50 false to laser in my LGT or in my wife's WRX, at least not without visible reason (i.e. LED-strobe nearby, etc.). As-such, I would imagine that my fellow LGT driver's woes are due perhaps also to a noisy electrical system.

[nomore55]

Over the past 6 - 9 months, my Passport 7500S has begun falsing on laser very frequently. I can't find any specific pattern to it. The 8500 X50 does not exhibit the same issue.

[kpatz]

I think it's a problem that crops up in certain 8500s and X50s. My friend has an 8500 that is the same way. In his Mazda5, it laser falses everytime he hits a certain RPM when accelerating. In his Audi, it falses when he honks the horn or opens the sunroof. We tried his 8500 in my car with my smartcord and got the same thing, but my X50 rev 5 doesn't false at all, in either of our cars.

I'm thinking there's a filter capacitor or something inside the unit that fails on some units, making them more sensitive to electrical noise. Next time we get together I'll experiment with ferrite beads, capacitors and chokes and see if anything can fix it.

[armscrafter1]

It's the ferrite bead variety of filter. I didn't know that's what it was called, but after reading the replies, found this interesting page that sums up operation pretty well: http://www.howstuffworks.com/framed....ec99/beads.htm

Apparently they are designed to keep noise IN the computer, but looks like they keep noise OUT of stuff as well. The only thing I would question if you make one and still have problems is the frequency of the interference. I may have blundered into the right match for my interference, but I suppose it could vary with vehicles. More background: The reason I thought interference is generated inside the electrical system itself is that a while ago I had my friend hold the x50 in different places in the car while I accelerated. It gave a false alert even if in the dark, on the floor away from the dash.

This page has pics of them on data cables:

http://computer.howstuffworks.com/question352.htm

but I would use one off a power cord, because you only want/need two conductors to work with.

I don't know what revision of x50 I have. I bought it in March '05. I think it was made in late '04, but not sure. It was serviced in March '06 for a bad antenna. (in all fairness, it was in a wreck and got wacked pretty good [not my fault not my fault!])

On another, slightly nerdy note, my first experiment was to insert a DSL filter in-line with the detector. They come in the box with a DSL modem so you can use you regular phone too. Got a "low voltage" indicator on the detector in V mode - so don't bother!

[Stealth 795]

Well my car sits at 14.8v on average sometimes going to 15v, due to my high powered alt. for audio amps.
Never had a false laser unless I use my power mirror.
I also have the rev 5 and the rev 3..
Had the rev 6.1 and never had any probs as well....
I am betting subaru's electical system is just loud.

[Orbital75]

Can you post a pic of the RF filter thingy you used?

I'm curious whether it's a choke, capacitor, or just one of those
ferrite beads you wind the cord around.

A friend of mine has an 8500 with the same problem, and next
time we get together we want to try a fix.

Snap-Together Ferrite Choke Core: $5.29


I personally haven't tried this but am considering it.
When I blow my Horn I get a Laser alert from my X50.....
Will this solve the issue. My Detector is wired to my fuse
box on the ACC fuse.

[MEM-TEK]

*****

[TSi+WRX]

armscrafter1 -

I'd like to pass-on some thanks coming from the LGT.com members. Those who've seen/are-seeing the issue are going to attempt your resolution.