weird r.a.p circuit issue

I have the oddest problem with an ’01 Chevy Camaro. I have put MANY stereos in Camaros as I have owned six F-body camaros myself but this issue has me scratching my head. Here’s the scenario: I have the head units ACC wire going to the factory radio ACC wire. This wire is controlled by the Retained Accessory Power (R.A.P) system. I also have a radar detector tied into this wire so it turns on and off by itself. Well, I wired up both the radar detector and head unit wire harness but only physically installed the radar detector. The R.A.P. circuit turned on the detector, as expected, with the key and turned off once you open the door because that kills the R.A.P. circuit so all seemed good. Then, a week later I physically put the head unit in the dash and connected it to the harness that had already been soldered in with the detector. Here’s where it gets weird: IF the head unit is ON and I take the key OUT of the ignition, the head unit and detector both stay on as expected. BUT, when I open the door, the R.A.P. circuit does not die like it should. Both units stay on. THEN, if I turn the head units power off, THAT finally kills the R.A.P. circuit along with the detector because they are both tied to the same ACC wire. I tried it again leaving the head unit on and turning off the radar detector but that did not kill the R.A.P. circuit. The car seems to sense the current change when the head unit is turned off (with the two amps turning off with it). But this is after the door is opened and the R.A.P. circuit should ALREADY be off. Then I tried closing all the doors, put the key and turn it back energizing the R.A.P. circuit; this time I left the head units power OFF and so only the detector turned on. Well, when I took the key out and opened the door, the R.A.P. circuit died as it should. If I do not have the head unit on but only the radar detector, the R.A.P. circuit works exactly as it should (dying when you open the door) I have tripled checked all the wiring and it is correct. I also noticed that when the head unit is on and you measure the voltage of the ACC line, it goes to 10.5 volts instead of staying near 12.5 when you take the key out and open the door (when the R.A.P. would normally die) That wire should be 12 volts or 0, not 10.5. This car has no electrical issues, is in mint condition and already had a different stereo in it and NONE of this happened. Why in the world would the head unit have ANY affect on the R.A.P. not dying when you open the door?? From my understanding the BCM does not use any kind of current sensing to control the R.A.P. The R.A.P. circuit dies by the key being turned off (or out of the ignition all together) AND either door opening; that’s it. With my last system that was designed very similarly, everything worked perfect. I could be blasting the stereo and take the key out of the ignition switch, sit there for a minute listening but as soon as the door opened, EVERYTHING died. Any GM guys out there seen this? Thanks, John

If the head unit has a capacitor on the ACC lead, then it would single handedly be powering the radar detector when R.A.P was turned off. Well, when I saw that the head unit and detector were still on, I metered the ACC lead and it was at 10.5 volts, as previously mentioned. But if the capacitor was powering things, it would drain and that voltage would drop, I would think pretty darn fast since the cap was powering the detector. Although the detector isn't a HUGE load, it is enough load to drain a small cap within 10 seconds dropping the voltage to say 8 or under causing the detector to turn off. As for the post about the turn-on leads: the turn-on lead in the system goes straight to energizing a relay which then sends the remote signal to the amps and fans etc. In fact, this part of the system was not rewired from the first system to this system. In other words, I disconnected the old head units turn-on lead from the relay and simply connected the new head unit to it. I have been doing car audio for 20 years and the wiring for this setup is pretty simple and straight forward so I am sure there is no wiring error. The capacitor theory is a very good one except I didnt think a cap would power things for this long. If the radar turned off after a second or so then it would make more sense. The Pioneer head unit does have one of those plastic things that snap-on to the red ACC wire lead close to the harness connector. It's not a fuse because its way too small. They are a pain to open but I always thought there was a resistor in there, not a diode?

Anybody else got an idea?

The radar detector has only two wires: a black to ground and a red that I tied in with the head units red AT the R.A.P. circuit from the cars stock wiring. I know for 100% that the radio's red wire and the radars red wire are tied together. The radar is absolutely not being powered by the radio's remote wire. An easy way to tell this is that the radar works perfectly when the head unit is physically removed from the car. Therefor there is no remote wire being powered. I do happen to have an identical spare head unit that I can plug into the existing harness thats soldered into the car. I'll see what happens with that. This whole thing just seems odd because I never experienced this with that last stereo which was wired up identically. The ONLY difference actually is that there was not a radar in the car. I added that with this install but why the R.A.P. circuit would care about a radar is beyond me.

Okay, I figured out what the problem was. The system has a Pioneer DEX-P9 head unit and a DEQ-P9 digital processor. Well, the processor was allowing 12v to feedback from it's B+ connection, through the processor itself, and back out of the remote wire feeding BACK to the turn-on relay. This voltage was essentially going back through the relay, back to the head unit and keeping it's ACC line hot therefor not shutting down the head unit. If I pulled the IP cable from the processor OR it's B+ wire OR it's remote wire then the system would shut off because it broke the circuit feedbacking back up to the head unit. Not sure why unplugging the IP cable affected it but it did. At first I thought the processor was faulty because it shouldn't be doing this. Well, I happen to have ANOTHER DEX-P9 and DEQ-P9 here. I removed the first set of equipment including the IP cables and fiber optic cables and put the second set in and it did the EXACT same thing. I couldn't believe it. Either I have two bad processor units (which I highly doubt) or these stupid things are designed this way. Anybody seen this issue with this equipment?