Viper 5305V Trunk Release Negative Output Problem, 1990 Ford Mustang

I recently installed a viper 5305v unit in my 1990 Mustang lx. I successfully was able to wire it up correctly and everything works great(locks, alarm, starter kill). My problem is the trunk release is not working no matter what I do. My car does have a factory switch for the trunk release and applying 12v to the purple and yellow wire on my factory harness will pop the trunk. I understand that the viper alarm has a red/white wire which is used for a trunk release and is a 200ma negative output. Using a 30/40 SPDT relay I tried every configuration and I cannot get a response powerful enough out of the viper system to trigger the relay. Using a cheap multimeter when I hold down the aux button on the remote it does show that it is pulsing but it doesn’t seem like it is enough. I am getting very low readings. On the 200m setting of the multimeter the highest pulse that I got while holding the aux button for a few seconds was 80.6. I tried multiple wiring techniques for the relay and none will trigger the trunk no matter what I do. I understand how relays work but for the life of me I can’t figure it out. I am unsure if I need to program another aux channel and use that for the output instead? I haven’t messed with the settings on the 2 way remote at all. I am lost at this point. When wiring the relay I used: pin 85 as 12v constant fused power Pin 86 as 200ma negative output from alarm Pin 87 as ground Pin 30 as 12v output going to switch for trunk Pin 87a not in use I tried also switching pin 87 ground for 12v constant power as well connecting together with pin 85 and I cannot get a response from the system at all. The negative output from the alarm does not ground enough to bridge the relay. Relay has been tested and works. What should I try next or test? Any help would be greatly appreciated.

The multimeter is probably not able to display the actual peak current since the pulse is only about 500 milliseconds. Are you certain that the relay contacts are not closing? Is your factory switch provide ground to the trunk release solenoid or +12V?

Yeah the relay is not closing at all. I took off the trigger wire from the alarm and added a chassis ground to it and the moment that happens the relay clicks. Put the negative output wire from the alarm and hold the aux button and nothing. The factory switch is just providing 12v and the trunk pops. There’s actually two wire pink/white with 12v constant on the bottom of the trunk switch and when you click the button 12v gets applied to the purple and yellow popping the trunk

Measure the resistance of the relay coil. The typical range is around 70-80 ohms. If you get a reading much lower than that, try a different relay. Also try one of the aux outputs as you suggested. Connect either terminal 85 or 86 to constant power and the remaining terminal to your aux output. As long as the relay clicks, you can wire 30 and 87 to the wires at the back of the switch. It doesn't matter which side is which.My ex once told me I have a perfect face for radio.

Just measured the resistance of the coil and got 88.7. Also applied 12v and ground and was able to get it to click so I want to assume it’s good. Also have another relay that was brand new and tried that as well but the results were the same. I messed with it more today and I used the aux 4 output that supplies the same 200ma negative output with no success either. Factory manual states that this channel should be pulsing as long as the command continues. Tried to wire it a few different ways holding the aux button for different time frames to see if anything changes and no dice. I am starting to think that I have a bad unit, it’s just strange that everything works except for the trunk release. I opened up the brain of the alarm to peak at the internals and nothing looks damaged or burnt. Not sure what I can do at this point?

Do you have an LED and a 1k resistor laying around? Connect the resistor in series with the LED. Power the appropriate leg of the LED, connect the resistor to the negative leg of the LED, connect the other end of the resistor to the alarm output wire in question. If the alarm wire has enough current capacity to illuminate the LED we can make this work with a single transistor and possibly a heat sink. Let me know if it lights up and I will find you a diagram.

For just driving the trunk release solenoid, a 10A miniature relay should do the job. Typically they have a 400 ohm coil. So your output would only need to sink about 35mA max. If it can do that, it is a lot simpler than adding a relay driver circuit.

Those are both great ideas. I think the source of your problem is a poor ground. How is the unit grounded/where? Address that, and it should work as designed. If you have a jumper wire with alligator clips, connect from your current ground point to the rim of the cigarette lighter socket (or any other known good ground). Then try the trunk release via remote.My ex once told me I have a perfect face for radio.

Wasn’t able to work on it anymore today but I do have some resisters and I will see if I have an led light to try that on hopefully tommorow. I’m gonna also try to locate a 10A miniature relay locally just in case as well as an alternative. That would be great if I could get that to work The ground for the alarm is a strong chassis ground in the driver side kick panel. I did try using a ground going directly to the battery but there wasn’t a change in the results. I can try it again just to verify. I will post some updates tommorow thanks for everyone’s input I really appreciate it

Little update, I was able to wire a 1k resister in series along with an led and using the output wire from the alarm and I was able to get the led to light up. It didn’t light up very bright but it did light up. It wasn’t a single led tho it was 7 leds built in to one so possibly that’s why it didn’t light up fully. How would I wire it if I wanted to use a resistor? As for the relay I ended up ordering a 10a mini relay and it will be here tommorow. I will be attempting to wire it again and see if I can get it to work.