Viper 791xv Shutdown Not Working

I've had a viper 791xv installed on my car for about 12 years now and have not modified anything on it, it has worked fine for a very long time but recently the brake shutdown stopped working. I traced the wire and tested for continuity and i have signal from the brake wire all the way back to the brain of the alarm, but still it wont shut down. I need some way of checking to see if the connector right at the brain isn't making good enough contact, or if the brain itself is not responding to the input. I should also add that the valet button fell apart and the tip of the button came out, now at random times the car goes into valet mode, without me doing anything.

Verify that there is 12 volts on that wire when you press the brake. Continuity is only testing the state of the wire. Black meter lead to chassis of the vehicle and red lead on the connection at the alarm brain. Should read 12v when the brake pedal is pressed.

Do the brake lights on the vehicle work normally? If not, check fuses for the brake lights.

I too have a 791XV in my F250 Super Duty. It was my first install back in 2008, with a major up-grade to the things it could do in 2012. It's been a good unit, and everything still works just fine, but the fobs have been POS almost since the get-go. We've had 4 of them at about $125 a pop. My last fob shot craps a week ago, now I can't access the system at all, so I ordered a 5306 to up-grade the entire deal, and be rid of the funky fobs. I may even retain the 791's remote satellite relay and connect it to the 200ma (-) outputs, as the wiring is all intact and good. I'll cleanly splice the new to the old's wiring, rather than re-do the entire install.

You listed a couple of age-related issues. I'm surprised the fobs weren't on the list. If you can't fix the brake shut down, consider an up-grade to a current model.
Cheers

Ok so I ended up testing the brake wire right to the brain of the alarm and it is getting signal. But todays new issue makes the car almost undrivable. The alarm wont respond to a disarm commands at all. I can see on the old style remote that the fob is putting out a signal, but the car wont respond. I had to drive to work this morning with my fob in my hand turning off the alarm about ever 30 seconds. How can i bypass this for the moment?

Unplug the module. Do an up-grade.

Will it not go into valet mode?

-------------
My ex once told me I have a perfect face for radio.

I'd try unplugging the valet switch completely to see if that helps solve the random valet issue. If it does then get a new switch since you said its busted anyway. New switches can be had on eBay for about $5 shipped. Search for "DEI valet switch"

To bypass the system temporarily you could unplug the brain but if the starter kill is wired up, you will need to jumper the starter kill wires in the heavy gauge 8 pin connector. The purple and green wires pin 1 & 2 will need to be jumpered together to be able to start the car while the brain is disconnected.

If it were me, I'd open the brain case and check continuity at one of the copper traces that connects to the incoming harness pin. Perhaps all the connector pins could use a solder reflow on the circuit board. While open you could inspect the board to see if any obvious components look like they may have burned out.

If you are able to determine that only the brake input is toasted and not repairable but the other functions all work properly, then I wouldn't swap out the whole unit. I'd likely remove the brake input wire and then use a relay to convert the + to a - and tie that to the hood input circuit using diodes to isolate it from the original hood input. They both report on zone 1 anyway when the alarm is triggered.

-------------
Steve G

iskidoo wrote:

---

The purple and green wires pin 1 & 2 will need to be jumpered together to be able to start the car while the brain is disconnected.

---

This is not true. In a 791xv satellite relay, the pur and green wires are on Normally Closed relay contacts. A 791xv will crank just fine with the module disconnected.