viper 5704 comm issue

So you have verified that it is simply the car running that kills the communication - that's an important accomplishment. Where is the antenna wire ran? You should avoid bunching the antenna wire up on itself. Disconnect all sensors and wire harnesses that are not being used. I would disconnect everything but power, ground, and the antenna. Perform the test again with the car running to see if you can communicate with the brain. What is battery voltage when the vehicle is running? Kevin Pierson

One you have rechecked all the H3 wires to vehicle and charging system is putting out good voltage(13v+) while running, Check for groung issues from motor to chassis, if you have poor motor grounds it can cause a imbalance in the electrical flow, verify good alternator ground. If nothing turns up then the next suspect would have to be the factory wiring has a issue. Can you try the remote starter with out the ignition switch shown in the pic to see if there is any change. Depending on the factory wiring harness you are using is it pulling all is current through the same wires that the remote start is to power everything.

One thought occurred to me, your first post said you connected H3/9 RED / black, you didn't mention H3/2 RED / white. From your photo it looks the other way round. Try connecting both AND take ALL of your power and ground feeds directly to the battery.

Yeah, Howie I read the first post multiple times and he isn't using the Flex relay at all, so no need for the H3/2 RED / White, but the other H3 direct to the battery I assumed he had already done by his previous post with the picture.

tylerwayne wrote: I doe have the RED / black and Red wire soldered together, running to the battery. I will go through again wire by wire with my multimeter to verify all voltages during start up.

I can't figure out what would be the cause of this, but I'm leaning towards some kind of issue between the engine harness and the vehicle harness not providing good power or ground if none of the other things mentioned to try don't solve the problem.

OK but that was the only thing that appeared wrong.

Ok, I will run the necessary 12V+ constant power wires to the battery directly as well as the ground. The antenna wire is stretched out and temporarily mounted on the rear bulkhead of the car. As for testing comm while engine is running (with ignition input/output hooked up) , the only comm it should be able to normally do is pit stop mode, and maybe temp sensor? What other comm features can I test while engine is running? Or are you saying to just hook up power and ground without a run/ignition input so the brain does not know the vehicle is running so I can test if the running vehicle causes RF interference? Good idea... I am out of town this week, but will hopefully be able to post an update Friday.

tylerwayne wrote: What other comm features can I test while engine is running?

The lock/unlock, Aux(Trunk), Panic, Temp, Status should all still work reguardless of it being started by key cylinder or remote start.

tylerwayne wrote: Or are you saying to just hook up power and ground without a run/ignition input so the brain does not know the vehicle is running so I can test if the running vehicle causes RF interference?

Yes, that would be another thing to eliminate for the comm. problem. At this point start with the most basic hook up power and ground direct to battery to viper with vehicle running and test comm. if it dosen't work then it's a vehicle interference issue. If it does comm. then add a wire and test again with vehicle running until you find a wire connection that is the cause. Then you can trouble shoot it. Start with the H1 red, black the add in this order,(neutral saftey to ground, H3 RED, PINK, RED / BLACK, VIOLET, Tach). Testing with each connection the comm. with remote start then key switch vehicle running. The viper will enter remote start mode as long as it is set to Automatic trans, the neutral saftey wire is grounded, and the neutral saftey switch is pluged in and on, but will time out if no tach is seen after 3 start cycle tries. Once you got the 4 H3 wires (RED,PINK,RED / BLACK,VIOLET) needed hooked up for engine to run with remote start, test comm. with viper again while remote started. If it is comm. fine then add the H3 ORANGE and so on. Testing each step of the way until the viper stops comm. again.

Guys, Interesting finds. SoI hooked up only the POWER, Ground and Antenna directly to the trunk mounted battery. Works for lock/unlock while vehicle is OFF. Engine running, no comm situation with remote. I connected and disconnected altenator and no comm either way. Second scenario. I took a second car battery, not connected to the carat all. Placed in trunk area and connected alarm power and ground only, again it is not wired to car. Turned car on and I am getting comm during engine is running. That test makes me disprove that there is an RF interference from engine. However there seems to be a wiring issue from the car to the battery? What do yall think? I am going to fully charge the car's battery and retest to confirm.

Check for inverted wires in the car, and verify all grounds for the engine harness, and the vehicle harness. Also verify proper function of Ignition switch, and that it's not resting any (+)outputs at ground when off.

lurch228 wrote: Check for inverted wires in the car, and verify all grounds for the engine harness, and the vehicle harness. Also verify proper function of Ignition switch, and that it's not resting any (+)outputs at ground when off.

The 12V+ at ignition switch is 0 OHMS to ground the Ignition and ACC posts both have about 20 OHMS to ground with no power supplied to them. The starter feed to start solenoid has about 5 OHMS to ground when off.