85 Cressida, Crimestopper 2011RS IV

Hey guys, maybe you can help me out.  This is killing me.

On the alarm part of the install, the docs say:

Green: (-) Door Pin Switch Input

Identify the wire that reads ground when any door is open and 12 volts when all doors are closed.  Some vehicles may have isolated door triggers.  In this case you may need to run additional wires from other doors or go directly to the wire that tribbers the vehicle's interior dome light.  Sometimes newer vehicles contain a separate body control module (BCM) where the door trigger circuit can be located.  Most vehicles will NOT require the use of BOTH Green and Violet (+) door trigger wires.

I can source +12 when all doors are closed.  But no wire in the circuit gives me a ground when a door is opened.  Even though the door pins ground.  The problem is the factory "Fade-Out Relay".  It handles all inputs from the door pins and also grounds the various lamps (dome, ignition key light, door key light, door open light, etc.).  Here's the killer... 

The dome light is on the following circuit (I have a factory electrical manual):

[Battery +]  ->  [fuse 7.5A]   ->  [dome lamp]  ->  [Fade-Out Relay]  -  [Ground]

I hooked up my Fluke DMM to ground (-) and pin 5 of the Fade-Out Relay (wire that comes from the dome).  I get +12.65 when doors are closed by an open circuit (no ground) when a door is opened.  The dome light does indeed light and the other tic-tac lights operate normally as well.

How can this be?  This is the most simple circuit in the world.  Now, I did dig the Fade-Out Relay from the passenger's kick panel and opened it up.   Fairly complex - no relays, lots of transistors, fully electronic.

Even when pulling a signal from a door pin, the circuit upstream (from the pin) has a diode and eventually terminated as the Fade-Out Relay, and registers a significant resistance. 

Even though my pins are negative triggered, I can't pull a ground from the circuit.

I had a 87 Supra with a fade out relay and I'm pretty sure they're fairly common in Toyotas from 85 - 92.  Anybody know the fix/workaround for this.  I'd call Crimestopper, but it's the weekend and I've been at this since Monday.  Don't laugh.  I must've put in 40 hours so far on this.  I don't know how the hell you guys knock out two or more of these things in one day!

Here is a scan of the light diagram.

1 meg picture

Thanks for any insights!

A added a webpage which explains more about my problem.

Thanks!  Post reply here, I didn't put an email link on that page.

Hey guys,

Got a fun one here.  Car: 85 Toyota Cressida.  Alarm: Crimestopper 2011 RS IV.

All works perfectly, except door unlock.  Car circuit requires a ground pulse to lock and unlock the doors.  Using diodes (mark to head unit).  Lock works perfectly, 100% of the time.  However, unlock has only worked a couple of times.

I monitored the head unit output with a multimeter and found that there really isn't a "ground", but rather a reduction in voltage, from 12+ volts to about 1.5 volts.  There never really is a continuity with ground.  I've tested this by running a needle through the signal wire 1 inch away from the CPU and have also taken the wire out of the connector and grounded it to check for proper wiring.

Any solution?  Would a voltage DROP from 12 to 1.5 fire a relay?

And I was thinking a ground was a ground...

My third post has my problem.  The first two posts relate to issues that have been addressed.

I think the moderator or whoever is making sure this stays in one post.  However, when people see "Cressida" in the title, they don't click. 

My problem is I have an unlock signal issue with a Crimestopper 2011 RS IV.

Thanks,

Thanks!  Will do that relay work-around.

A general question regarding the problem that spurs the addition of the relaly - is it "normal" for a head unit to DECREASE the voltage and call it a ground signal?!

Secondly, will the output of 1.5 volts (what Crimestopper calls a "negative pulse") energize a coil in a standard 30A relay? 

Lastly, I understand that grouping of disparate threads into install-based threads.  Makes sense.

Thanks again,

Yes, head unit = alarm CPU.

I'm using a digital multimeter.  The voltage at rest is 12+ volts.  When the "negative pulse" is set (programmable from .75 to 3 seconds) voltage drops to 1.5 volts.  I tried to measure contunity with ground testing the same unlock event and continuity never measurable. 

Welp, I proved the concept.  The relay works.

A tech note for the archives...

Old Toyotas (mid-late 80s) with factory power door locks REQUIRE a relay to deliver the ground signal.  They also require two ground pulses.  The pulses must be shorter than 3 seconds.

I got it to work by programming double pulses @ .75 seconds.  The Crimestopper unit only allows for .75 and 3 second pulses, so I can't give you the exact cut-off point.

Whew!  Everything works.  Now, I gotta put the whole thing in for real.

Any idea on how to pull A pillar trim to mount the antenna?