556U interfering w/ Viper 791?
Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=45098
Printed Date: May 20, 2024 at 4:38 AM
Topic: 556U interfering w/ Viper 791?
Posted By: ampere
Subject: 556U interfering w/ Viper 791?
Date Posted: December 13, 2004 at 8:27 AM
This is officially the second Ford vehicle I've seen this problem in. When the car is remote started, sometimes (about 80% of the time), the remote fails to work afterwards. I can have it 3 inches away from the antenna and still nothing. I get the out of range icon. The moment the car start timer goes off, the remote is 100% functioning again!!!!! Could the 556U (RF) security bypass be interfering with the remote's RF??? I am so confused!!!! Plz help!
Replies:
Posted By: meltingplastic
Date Posted: December 13, 2004 at 2:44 PM
i can tell yuou that on my uncles 97 f150 that i put a remote start in... on the factory fob.. if the truck was running and you tried to use the keyfob.. it wouldnt do anything. so check to make sure where u are tapping in for lock and unlock... if the viper fov doesnt even let you stop the vehicle.. then i have no idea were to help you with that
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Driving a Bagged, Caddied 02 s10
Posted By: ampere
Date Posted: December 13, 2004 at 3:40 PM
Unfortunately, the fob doesn't let me do anything. It's like it cannot communicate with the alarm brain at all. Sometimes if I press a button (arm or disarm) repeatedly for 15 seconds or so, it will work. Any other ideas/suggestions I could try? Anything would help, thanks!
Posted By: auex
Date Posted: December 13, 2004 at 3:57 PM
Try and make sure that no part of the alarms antenna is anywhere near the box for the bypass. Also check the alarm's ground.
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Certified Security Specialist
Always check info with a digital multimeter.
I promise to be good.
Tell Darwin I sent you.
I've been sick lately, sorry I won't be on much.
Posted By: kgerry
Date Posted: December 13, 2004 at 4:19 PM
i've had a few weird vehicles like that....when running, something generates this weird RF blanket... last one i tracked down to it being the blower motor... it sounds like something is running on the same frequency.... you may want to buy an RF sniffer and put it to the test
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Kevin Gerry
Certified Electronics Technician
MECP First Class Installer
Owner/Installer
Classic Car Audio
since 1979
Posted By: ampere
Date Posted: December 13, 2004 at 4:21 PM
auex]T wrote:
y and make sure that no part of the alarms antenna is anywhere near the box for the bypass. Also check the alarm's ground.
Thanks for the reply. I made sure the antenna and it's wire is not routed anywhere near the box bypass.
The ground is good. Is this theory of the security bypass affecting the remote even a plausible idea? I mean, could there technically be some RF interference?
Posted By: meltingplastic
Date Posted: December 13, 2004 at 4:24 PM
did you try using the fob when started with the key.. not the remote start... that way the 556u wouldnt be activated and would tell you if it possibly has something to do with the 556u unit
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Driving a Bagged, Caddied 02 s10
Posted By: ampere
Date Posted: December 13, 2004 at 4:29 PM
kgerry wrote:
i've had a few weird vehicles like that....when running, something generates this weird RF blanket... last one i tracked down to it being the blower motor... it sounds like something is running on the same frequency.... you may want to buy an RF sniffer and put it to the test
I am going to turn on/off a number of different components and report back shortly.
Posted By: ampere
Date Posted: December 13, 2004 at 4:29 PM
meltingplastic wrote:
did you try using the fob when started with the key.. not the remote start... that way the 556u wouldnt be activated and would tell you if it possibly has something to do with the 556u unit
I'm going to try this and report back shortly.
Posted By: ampere
Date Posted: December 13, 2004 at 4:40 PM
ampere wrote:
kgerry wrote:
i've had a few weird vehicles like that....when running, something generates this weird RF blanket... last one i tracked down to it being the blower motor... it sounds like something is running on the same frequency.... you may want to buy an RF sniffer and put it to the test
I am going to turn on/off a number of different components and report back shortly.
Well I tried it a few times with evey component I could think of turned off, HVAC, Radio, any lights, and i still have the same problem.
I think my next step might be to get a RF sniffer.
Posted By: ampere
Date Posted: December 13, 2004 at 4:43 PM
ampere wrote:
meltingplastic wrote:
did you try using the fob when started with the key.. not the remote start... that way the 556u wouldnt be activated and would tell you if it possibly has something to do with the 556u unit
I'm going to try this and report back shortly.
I just tried this:
1) Start vehicle normally.
2) Wait a bit.
3) Press remote start button Result: Alarm will work perfectly and take over so I may remove the key. I repeated this a few times and never had a problem.
Posted By: meltingplastic
Date Posted: December 13, 2004 at 6:55 PM
u were able to take over but were u able to still use the keyfob.. ie lock the doors or stop the car
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Driving a Bagged, Caddied 02 s10
Posted By: ampere
Date Posted: December 14, 2004 at 9:00 AM
meltingplastic wrote:
u were able to take over but were u able to still use the keyfob.. ie lock the doors or stop the car
Yes, if I start the car normally, all of the fob's functions work perfectly.
Posted By: 91cpe
Date Posted: December 14, 2004 at 3:32 PM
I wonder if the alarm is wired to the power output of the the rs unit to keep the alarm from sensing the motor starting?
Never installed a 791 but on the valet r/s unit they list the yellow wire as an alarm power input wire. When you initiate r/s the valet cuts power to the alarm so that it's not trigged by the starting of the vehicle. Perhaps they wired the 791 combo unit this way?
Posted By: massivegrk
Date Posted: December 14, 2004 at 11:50 PM
did a rsx the other day and had the same problem.. it worked fine a few times until i programmed one of the wires for defrost... the 556u says to connect the blue wire to the status output of the remote start.. which happens to be the defrost output on a 791xv.. so if you have that wire setup for anything else it wont' be giving the negetive latch the 556u relay needs to activate.. try grounding the blue wire from the 556u and trying to remote start the car.. if that works... just connect the wire from 556u to the pink negetive relay output from the 791 remote start relay module. Didn't read a good amount of the posts, so hope this is what you were looking for
Posted By: massivegrk
Date Posted: December 15, 2004 at 12:00 AM
hmm was looking over the manual for the 791 guess i missed that it did have a dedicated negetive status output that i missed.. I just connected the blue from 556u to the wrong wire(blue/white) when i started. Don't know if you did the samething. I see that there is a blue wire at remote start module and you can just connect it there instead of at the pink
Posted By: ampere
Date Posted: December 15, 2004 at 9:02 AM
Well, I am not using the blue status wire for any other device (defroster or whatnot).
I've trippled checked all my wires and sarted tearing hair out! Wonder if I have a faulty part.
Posted By: bbeach15
Date Posted: December 15, 2004 at 11:08 PM
some fords turn off the locks when the ignition is on, you can not use remote locks with the engine running
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