791xv and truckpc

I have my truck outfitted with a windows computer. i currently have my a/c heater controls turn on when the remote starter starts. my pc turn-on wire is hooked to those hvac controls, so whenever i either start my truck remotely or with the key the pc will turn on. this works great, but there are times when i want to start my pc remotely too- without the truck starting. problem is i cant think of a good way to do this. best thing i can think of is to use the ACC button on the remote, and have the 791xv power up a relay that feeds the pc straight battery power.   im just not sure if im overlooking something or if there is a better way...

you know thats not really going to do it, because it appears the ACC button will only stay active for as long as i keep holding the button down. my power supply works by seeing the ign "on" and it powers the pc up intelligently. so i need to fool the power supply into thinking the ign is on when it really isnt. i need a function off the 791xv that stays on until i tell it to shut off... i suppose i could just use the door lock buttons, im not using them right now as my locks dont work electronically anymore.

argh.. ok, i figured it out. mostly. program channel 4 on the 791xv for LATCHED mode. i can do this, even with the stupid button pressing procedure and all... and get the power for that relay right off the battery circuit that powers the pc- ill use a diode to keep it from possibly backfeeding. my only problem now is, how the heck do i activate channel 4 by the remote? is it one of those things that only works once you program it? by default, its in 'validity' mode, and pressing AUX on my remote just chips, it doesnt show any specific numbers...

you need to press lock + aux at the same time to activate channel 4. right now it will only be on for as long as you hold the buttons down but when you set it for latched it will stay on with just one press and turn off the same way.

Sounds like you've got this mostly figured out already. But yes, connect the channel 4 output from the Viper to a relay, configured for positive output. Actually, you want to ONLY turn on the computer with Channel 4, but you want to avoid turning on other things, such as the car's climate controls, correct? You can do all that with one relay, without a diode. First, disconnect your computer's turn-on wire from the HVAC accessory wire in the car. Next, make your relay like this: 86: Channel 4 from Viper 85, 87: FUSED constant power 87a: connect to HVAC wire in car 30: connect to computer's power input. HOW IT WILL WORK: When the relay's off: It'll work the same way as before you did this. When you turn on the key (or remote start), power from the HVAC circuit enters 87a, exits through 30, and powers up the computer. When you hit the AUX button on the Viper: The relay energizes, breaking the contact between 87a and 30. Power will flow from 87 to 30, turning on the computer. Power will NOT flow to 87a, and therefore the HVAC in the car will remain off. PROGRAMMING YOUR VIPER: You probably want "latched," or "latched, reset with ignition." Latched: Press the remote to turn on, press the remote again to turn off. Latched, reset with ignition: Same as above, except, if you turn on the computer by remote, then get in the car and start the engine and drive away.........when you complete your trip and shut the car back off, the computer will shut off too. P.S. "Latched" will stay on indefinitely, until the battery dies. If you think there's any chance you'll forget to turn it back off, you might consider mounting a small but bright LED in the window of your car, or even wire up the system to turn on the parking lights or hazards whenever the computer is on, as a reminder.

heh, i rambled a lot and really didnt think anyone would respond.   youre awesome man. i came to a new conclusion. why power it off the hvac at all? the 791xv has 200ma(-) outputs for ignition and aux4... so why dont i just power a relay off battery 12v+ power, and tie both ign and aux4 remote outputs to the same relay (use diodes to keep the remote feeds separate for extra safety) wouldnt that work just as good? that way i think it would start the pc if i do one of three things- turn the engine on by key, by remote start, or by remote aux.   and it would NOT turn on if i just put the truck in acc on the ignition (good so i can just listen to the radio while leaving the pc off) i think this would be the easiest, most flexible way...

ok that wont quite work. the 791xv doesnt even really turn on unless you engage it with the remote... so using one of the (-)signal outputs wont help in that case. and, the ch4 works, but it only stays latched for as long as i hold the button on the remote. i think that is its default setting, but no matter how many times ive tried to change it in the feature learning routine, it doesnt change the behavior. so i have two problems now. 1. i need to find a way to start the m2 with the ignition again.   if i hook up a REM wire from my radio i am worried about crossing that with the aux 12v+ when that is active too... i dont think it will hurt anything, im just not sure. 2. figure out why i cant program ch4 to be in 'latched, with reset on ign'. it stays in momentary mode no matter what settings i use.

well all problems fixed now but one. the damn 791xv simply wont let ch4 get out of 'validity' mode. it only works if i hold the button down, it wont latch by itself. i have tried all the options in the setup too... very frustrating....

This is utmost frustrating! i know im doing it right. 2nd menu, 10th step... thats for ch4 according to the manual. 11th step is channel 5.   and each channel should have 5 choices, but when i try to program either channel i only get a maximum of 3 choices- so its like im not even in the right menu. furthermore, no matter what of the 3 choices i pick, nothing changes the behavior for ch4, so i MUST be in the wrong menu. are there different versions of the 791xv that i dont know about? possibly im looking at the wrong manual?   if only i had a bitwriter, this would be easy. but it should work manually too, its so frustrating!

I've been using Audiovox since 2001, so my DEI/Viper days are long behind me, although I've installed/repaiRED / reprogrammed a few over the years for friends. I supposed you could always find a local installer who has a Bitwriter, and see if you can pay him a little money to program it for you. I don't know if there were different models/version of the 791xv. I would say probably no, because that model wasn't on the market all that long. Any link to the install manual?