improved dei 508d

I installed a DEI 508D under my center console in my truck with a Viper 5900. All was working fine until I am have been getting false zone 2 warnings and a couple full alarms. I think these are coming from the DEI 508D, as I have read on this board that it may have falsing issues?? I disconnected it a couple of days ago, and so far no false alarms.

I really like the idea of these units, and I know some just install the warn away (green wire). I would like both because the door is usually left open once it is broken itno and the door pin would be bypassed.

I got a second 508D for the wife's car before I noticed the false alarms were occuring. She doesn't want it now. So I was thinking of installing two 508D's (NAND'ing the outputs to the alarm) in hopes that they would not false trigger at the same time.

Has anyone tried this type of install? Would the "beams" interfere with each other? What are the odds of them fasling at the same time?

Plan B, would be to install a better device. Anyone know of a similar device that doesn't give false alarms? 

i also find that you can't mount where they can see metal in any direction except the bottom

if metal is close the them i find that they have more of a tendancy to false

also thing that hang from your mirror ar great for falses

Well I could try and re-adjust the zones as suggested.  I have this thing installed in a small two seat pickup, under a plastic console that was removed when the zones were set up. Being a small truck, the back wall of the cab is 8-12" behind it. I have it tie wrapped securly to the carpet.

I can't remember if I tied into the 12V line of the shock sensor or tied into a seperate 12VDC line. I will double check, and change to a seperate source, but not that it the problem.

I do have a a small pouch hanging from the mirror to store my sunglasses. I will remove it and see what happens. Last resort (ripping out vinyl head liner will be a pain) is mounting in roof.

I don't think I buy the need of a diode on these things. I was bench testing a spare 508D and determined they must  have open collector outputs (transistor). I attached a 10K Ohm from the green wire to 12VDC and scoped the other end of the resistor (collector end). Saw the line trigger (12 V to gnd) when motion present.

I bet the shock sensor output is the same. The only way these devices can trigger the output lines, is with a valid trigger signal on the sensor side (which then drives the transistor base), thus paralleling the outputs should not back feed throught the outputs to the inputs of these sensors.

I assume the trigger line(s) in the alarm brain to be the low side of an opto-coupler input ("LED" side), with the sensors completing the electrical path by turning on their o/p transistors.