791XV remote start hot weather problems
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=81306
Printed Date: July 12, 2025 at 3:16 PM
Topic: 791XV remote start hot weather problems
Posted By: jroymd
Subject: 791XV remote start hot weather problems
Date Posted: August 07, 2006 at 9:09 AM
I have a Viper 791XV alarm with remote start professionally installed in a 2005 Infinity G35 automatic transmission coupe. The remote start feature fails to fully start the car in extremely hot weather. I live in Florida and have to park in a parking lot that is exposed to the heat of the sun. Needless to say, the interior of the car gets quite hot. After several hours in the sun, when I initiate the remote start feature (after disarming the alarm), the starter solenoid and starter motor engage, but the engine fails to "catch" (for lack of a better term). The starter motor goes through the same cycle three times, then the alarm/remote starter disables any futher automatic attempts in that series. If I cancel the attempt during this failed series with the responder remote, I can start the car manually with the "computer chip" transponder key. If I don't cancel the attempt, I will often have to go through an alarm arm/disarm sequence before the car will manually start with the key. All other features of the alarm operate perfectly in direct sunlight. If the car is parked away from the heat of direct sunlight, the remote start feature works every time. The alarm main module is mounted under the dashboard away from direct sunlight. There is a dedicated "computer chip" transponder key that has been sacrificed in the transponder bypass module.The main alarm unit has been replaced with no correction of the problem. Questions placed to the manufacturer's tech support line have have yield no answers. It seems that the main Viper 791XV module is not the problem, since replacing the unit with a brand new one has not solved the problem. The only thing I can think of is that the heat has somehow interrupted the pickup of the signal from the dedicated transponder key to the main alarm unit. Has anyone else experienced such a heat related problem with the remote start feature of the Viper 791XV alarm?
Replies:
Posted By: captainzab
Date Posted: August 07, 2006 at 11:06 AM
Try making the loop that goes around your key cylinder smaller. If this doesnt solve it, try moving the 556U to a cooler position.
-------------
Note: You Always Dont Get What You Pay For.
Posted By: KarTuneMan
Date Posted: August 07, 2006 at 11:29 AM
I know these cars have 2 starter wires.....in the cold, without both, the car will NOTstart. I don't know how this might apply to HOT weather? I'm guessing....if you can't tell? Any of you DEI guys out there think any problems could come from that tiny little relay pack? HOT and small? You might also try this. In a controlled area (safe to avoid theft) put the key in ...(I don't know how the smart key works) and let the car sit in the sun and get as hot as possable. Then try to remote start. ??? again, just stabbing in the dark, about what to maybe look for.
Posted By: Chris Luongo
Date Posted: August 07, 2006 at 3:34 PM
jroymd,
Since you had the system professionally installed, hopefully the install shop will warranty their work, and fix the trouble.
In any event, there's a test you can make yourself that will GREATLY help the shop fix it........since it is an intermittent problem, it'll probably work fine when you bring it into the shop, which makes it tough for them to troubleshoot.
Anyway:
Near the left AC vent is a small LED light. First, you should know how it operates, and then you can make a couple of simple observations.
Take notice that when the car is off, the light flashes slowly. When you lock the car, the light comes on steady for 30 seconds, to indicate that the factory alarm is arming.
Also, insert the key, and turn it on----you will notice that the light goes out, and stays out. When you turn the key to the Start position and start the engine, it STILL stays out.
Next, wait until one of those hot days when the remote start is going to fail.
Watch the light, and try the remote start.
--If the light is OFF when the remote starter is on.....that is normal........the installer's transponder-key bypass is okay........he might consider a poor tach connection, or poor connection to the car's second-starter wire.
--If the light is steady ON when the remote starter is on, that means the car is not "seeing" a valid transponder key.......
most likely all the installer needs to do is slightly reposition the transponder bypass module's ring of wire that's around the car's keyhole.
Nissan/Infinitis aren't too fussy about the position of the ring, so it shouldn't be difficult to get it right.
If you were my customer, and because the problem is intermittent, I might consider replacing the ENTIRE bypass module and all of its parts, just to ensure that you wouldn't have to come back.........but it really is most likely the ring, so if they just reposition it, that should be good enough.
Posted By: jroymd
Date Posted: August 07, 2006 at 7:01 PM
Chris, I greatly appreciate your input. It is obvious you are familiar with this vehicle. I have tried the first half of your suggestion. Now I have to wait for another hot day to test the rest of the sequence. My only question is how does the repositioning of the key cylinder sensing coil help with the keyless remote starting sequence prior to insertion of the key? It is my understanding that the sensing coil around the key cylinder sends a signal back to the 556u transponder bypass unit after insertion of a properly encoded key into the key cylinder. (A signal is also sent to the factory transceiver depending upon the factory setup.) This should in turn initiate a signal back to the 791XV main unit and informs it not to trigger an ignition "kill" signal and interrupt the maintenance of engine RPM so a properly coded key can allow the vehicle to be driven. So how would adjusting the cylinder coil affect the sensing of a key that is not there? (Of course, there is the possibility that I am completely wrong, also.) Once again, many thanks from a very hot place. At least there aren't any more ice storms.
Posted By: captainzab
Date Posted: August 07, 2006 at 8:38 PM
The 556U sends the same set of "code" from the key inside to the car. What recieves the code is the key cylinder.
Nothing is sent back and forth to the key or anything.
If the code is recieved and correct, it allows the car to turn over. Therefore, by securing it better or shifting it allitle, will allow a better chance of it recieving the code.
The 791 does not know if there is a transpoder or not, it will keep trying to remote start (for 3 cycle)
-------------
Note: You Always Dont Get What You Pay For.
Posted By: Chris Luongo
Date Posted: August 07, 2006 at 10:17 PM
Yes, captainzab is correct.
The remote starter has no way of "knowing" whether the transponder bypass is working correctly or now...............all it "knows" is that it tried to start the car, and the car wouldn't start.......it makes two more attempts, and that's it.
The 556U (or similar) transponder bypass module is nothing very special. I often make my own when I'm out of stock.
It's just a bunch of loops or wire wrapped around your spare key........another bunch of loops of wire around the car's keyhole.........and a relay that connects the two loops together whenever the remote starter is turned on.
I might be mistaken about how the car's transponder key works..........but I believe, that the car puts out a signal that excites the key......the key sends a signal back........the car reads it, approves it, and allows itself to start.
Those two loops of wire allow the car and the key to "talk" to each other when the remote starter is on.............if there is a problem, the car will assume it is being stolen, and it won't start.
Posted By: jroymd
Date Posted: August 08, 2006 at 12:57 PM
Thanks again to Captainzab and Chris for explaining the 556u system to me. I'll try your suggestion at my earliest possible time.
Posted By: jroymd
Date Posted: August 10, 2006 at 6:10 PM
Chris, I now have the full sequence of events: -- On a cool day, the red LED remains off during the remote starting sequence, and the engine starts up successfully. -- On a hot day, the red LED is continuously glowing during the cranking cycle, and off in between cranking attempts. The engine does not start when the red LED is glowing. I guess you are right. As you stated, the car must not be "seeing" a valid transponder key. I 'll work on correcting this problem. ---- Again, many thanks for your knowledge and help.
Posted By: bmwpwner
Date Posted: August 11, 2006 at 11:30 PM
wow, i just finished reading this post and am very interested in what is going on with this vehicle. my question is to Chris, what is making the difference between the vehicle starting at different temperatures? are you thinking that the heat is changing the ring position somehow or is it possible for extreme heat to change the resistance in the transponder key? or is it something completely different? very interesting situation but i will keep an eye on this one to see what turns out to be the problem. btw, do you think that maybe jroymd is changing his HVAC controls differently depending on where the vehicle is parked and somehow the installer maybe got onto the wrong wire and that is what is causing all the problem. very interesting. ------------- "I cannot teach anybody anything, I can only make them think."
-Socrates-
Posted By: bmwpwner
Date Posted: August 11, 2006 at 11:36 PM
also, could it be that when this vehicle is parked in the direct sunlight the light sensor for the daytime running lamps could be what the installer taped onto for the 556u?
-------------
"I cannot teach anybody anything, I can only make them think."
-Socrates-
|