confirm neg door triggers

I am installing a compustar p2w900FMr-AS in my 2002 F250 Superduty 5.4L with factory Keyless. I have the alarm mostly working and the remote start is good. I have an issue with the dome light so the dome light isn't working for my door trigger.

I mapped out my wires, here is the link to it [url]https://www.ford-trucks.com/forums/attachment.php?attachmentid=10773[/url]

Please confirm two things for me, this is a negative ground and I install the diodes so the band (cathode) is on the truck side and the anode is on the alarm side?

I'll Try this againChart

Yes

Thanks, but I still need some help doping this out.

I taped each of the four wires with their own 18ga wire. I put a diode on each wire, cathode stripe towards the doors anode towards the alarm. I verified (-) trigger in the brain. It didn't work, all doors closed the alarm thought a door was open. So I tested. I found two diodes that read +1v on the anode when only the cathode was hooked up. I replaced those two. Here are the results of my testing, and it still doesn't work like it should.

The cathode is connected to the door switch and factory system, anode not connected to the alarm yet.
Tested to ground.
All doors open, Key on
ylw/blk Cathode 10.48 anode -0.29
Gry/Red Cathode 10.50 anode -0.17
Grn/Ylw Cathode 10.46 anode -0.06
Pnk/Grn Cathode 10.40 anode 0.19v

All closed, key on
ylw/blk Cathode 0.015 anode 0.001
Gry/Red Cathode 0.021 anode 0.003
Grn/Ylw Cathode 0.006 anode 0.004
Pnk/Grn Cathode 0.012 anode 0.007v

All closed, Key off
ylw/blk Cathode 0.010 anode 0.001
gry/red Cathode 0.018 anode 0.002
grn/ylw Cathode 0.003 anode 0.003
pnk/grn cathode 0.008 anode 0.005v

All open, Key off
ylw/blk Cathode 7.48 anode 0.027
gry/red Cathode 7.46 anode 0.040
grn/ylw Cathode 7.44 anode 0.999
pnk/grn Cathode 7.49 anode 0.942v

Which tells me that the alarms should see a very good ground when the doors are closed. Neg trigger?

So now I hook each wire up the alarm separately. It's late so I haven't tried each one on the remote to see what the alarm brain thinks, but I haven't solder it up yet so it's on the list for tomorrow.

As I said each wire to the alarm door wire separately, metered at the anode.
Ylw/blk open 4.698 closed 0.536
gry/red open 4.698 closed 0.530
grn/ylw open 3.098 closed 0.507
pnk/grn open 5.221 closed 0.528

Looks pretty good to me, when the doors closed the alarm senses ground and fairly even. My meter is pretty good (fluke 117), but I don't expect the alarm will know the difference in even a couple hundredths of a volt.

So I tied all of the wires together, the four door wires and the alarm sense wire and metered them to ground.
All doors closed 0.468v
All doors open 4.704v
looks good to me so far, but this is what confuses me.
LF only open 0.476
RF only open 0.478
RR only open 0.480
LR only open 0.489
Both rears open (fronts closed) 0.509v
Both Fronts open (rears closed) 0.492v.

I did something wrong, but I can't figure out what it is tonight. All of the anodes are connected together to go to the sense wire, the cathodes of each wire go to their own door. In this config (which appears to be right) I will always have a ground if a door is closed.

I think I need to reverse the polarity on the alarm, when all doors are open it thinks the doors are closed.

You've missed out on 4 diodes, the control box goes to sleep, wakes up and sends a pulse through the system. where you've joined, before your join place a diode between your join and the control box, ie away from the switches, so that the band on the diode faces towards the alarm join. If you've picked up trunk and hood at the same point do them as well, failing this look up directed's 1076door_pin_isolation.pdf Hopefully I've downloaded the file to you, ah well this topic hasn't come up for a few months. That diagramme should be on the forum somewhere.

Ok, I tried just the drivers door to see how it works. The brain is still on Neg trigger. I have the diode in so that the anode is toward the body module, the cathode connects to the door wire and the cathode of my spliced for the alarm. The alarm is still inverted. With the door open, the brain shows 0.5v and closed the brains shows 4.7v, however the remote shows the door is open when it's closed and the remote shows the door closed when the door is open.

I am getting frustrated.

One door all dioded up, metering where I should splice into the alarm sense wire. When the door is open I have infinite resistance to ground. With the door is closed I have 2 million ohms to ground.

https://www.the12volt.com/diodes/diodes.asp 

From Howie's post:

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the12volt • Support the12volt.com

As an experiment, using only the blk/ylw wire. I metered at the end of the splice (after both diodes) without the brain. Door open 0.012v/infinite resistance and closed 0.001v/2.379m Ohm.
<BR><BR>
On the factory wire closest to the door switch (before diode), Closed 0.010v and open 10.16v.
<BR><BR>
I switched to positive polarity because I only care when the door opens not when it's closed. I metered on the cathode closest to the VSM.<BR>
Open 1.8v and closed 0.012v. As a plus the brain acted correctly, the remote showed the door open when it was open and closed when it was closed.<BR><BR>

Please help me understand how it's inverted?

I reversed my connections on the ylw/blk wire and only used it for the alarm. It works as it should, but I have the anodes of both resistors to the door trigger. Diodes screwed me up in class, so is this right?

I got it, thank you all for your help. Any one door will trip the alarm now. I also think I am beginning to under why too. Guess I should have stayed for Advanced MECP.