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no ACC power; not ignition switch & not fuses!?

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  • no ACC power; not ignition switch & not fuses!?

    Hey guys, I searched and browsed many threads for ideas to narrow what may be my problem, and i'm about out of ideas
    My teg is a '90 GS hatch with a '92's b18a1, kept the obd0's ECU, distributor, injectors... this car's been 100% reliable for about a year until this week.
    I believe my problem may have started when I jumpstarted my buddy's car with mine; however, this was the 3rd time i've jumpstarted his car, so i'm not sure whether jumpstarting another vehicle is related to this problem occuring, or this problem simply happened on the same day:

    My teg has working interior(dome/door ajar & map lights), exterior lights(headlights & brake lights), and hazard lights in the "off" [O] ignition position.
    All electrical functions work in the "on" [II] ignition position (such as the blower, clock display, intermittent windshield wipers, turn signals, rear defroster... i'm sure i'm forgetting to list something but my point is that the electronics work in this position). The only thing that didn't work at first try in the "on" position was my head unit (Pioneer brand), so i narrowed that down by wiring both the +12v and the ACC wire from the stereo to the car's +12v and it works fine.

    This brings me to my problem that has me clueless: when my ignition switch is in the "accessory" [I] position, the constant +12v accessories (such as the exterior/interior lights, brake lights, hazard flashers, & the door ajar beeping) that work in the "off" position still work, but nothing that specifically works in the "ACC" position works (such as the blower and the stereo... i can't recall what else should work in ACC, the intermittent wipers? anyone want to add to ACC-specific functions?).
    My first thread search gave me the idea to check all possible under-dash fuses: fuse 22, fuse 14, and the 40amp heater motor/accessory fuse.
    Turns out all of these fuses were fine; I both jiggled and tried new ones with the 10A & 15A fuses. I verified the larger 40A fuse was good by swapping it with the other 40A fuse in my car's under-hood fuse box. i've inspected all other fuses <25A and they all aren't blown.
    My next thread search suggested that my ignition switch could possibly be corroded up and not making good connections when in the ACC position.
    I have a decent understanding of electronics, and i fixed the ignition switch on my previous car by the DIY method, so I removed & disassembled my ignition switch and roughed up all the contacts inside of it with a steel brush. I considered putting some vaseline over the contacts so they'd never corrode again, but I didn't in the interest of time (been scratching my head over this electrical problem for ~12 straight hours and counting).

    From the process of elimination, i'm quite sure that the following items are NOT the problem with my vehicle: fuses, head unit, ignition switch, ICU (the rear defroster, driver's side door opening turning the dome light on, and headlights on/engine off ding all work, so ICU appears to not be a problem)

    I currently don't have a multimeter, but my last guess is that there could possibly be a short somewhere in my ACC wire. But if this was the case, wouldn't a short in the ACC blow my under-dash 40A fuse, or some other fuse?!? If this type of short wouldn't blow a fuse, where is the next hop my ACC signal makes after the ignition switch, the fuse box? Does the ACC signal go to the head unit from there?

    If there's a thread topic or a common solution that i've totally overlooked, i'd really appreciate it if someone could inform me. My car's electronics and wiring are 18 years old, so do you guys think I should try and run a new ACC wire thru the car? I've got to head back to college this saturday, so i'm really trying to fix this problem while i'm on t-giving break and i've got loads of free time on my side. I'm open to the wisdom of veteran G2 owners

  • #2
    Kind of got lost with all the info.

    So I understand, your accessories, [radio, blower and so on] work when ign. switch is in the run, [on] position, and when engine running but not if the ign. switch is in the ACC. position, is that correct?

    If so, it must be the ign. switch, as everything is common after the switch, so if the accessories work when ign. switch is in the run position but not when in the accessory position it has to be the ign. switch, I can thing of nothing else that could cause the above problem.94


    • #3
      i'd rather be overly descriptive, than not be descriptive enough and have to play reply tag
      Yes sir, all my accessories are working fine in the "run" position (except for my cd player, since it needs a signal from both the ACC & the constant +12v wires), regardless of whether my engine is running or not.
      Darn, I thought that taking apart my current ignition switch and refreshing the contacts would be sufficient. But, what you said makes perfect sense, since my clock doesn't display in the ACC position, as well as my HU not getting the ACC signal...
      -I'll replace the switch and reply as to whether that fixes my trouble!

      If there was a short in my ACC wiring somewhere, it'd most likely blow fuse(s), correct?

      I appreciate the accurate & timely reply!


      • #4
        Yes a short in the system would blow fuses, and would if ign. was in ACC or run.

        I would still test the the output from the ign. switch before I spend money on something, even if it seems that it can be the only problem, all you need is a test light, you can get one for a few $ at Radio Shack, you can get a multimeter there for $20.94


        • #5
          Today I used the information about ignition switch wires from and I checked for signals where the 4-pin ignition switch harness plugs into the under-dash fuse box.
          I used my head unit as a sort of test light, by leaving its +12v wire connected and touching different wires with the HU's ACC wire. At first I expected the "ACCESSORY/HEATER BLOWER 1" (yellow) wire to be hot with the ignition in ACC position, but it was only hot when in "run". My next guess was for the "IGNITION 1" (black/yellow) wire, but there wasn't that color wire in my harness I'm guessing either my ignition switch is aftermarket or the website has incorrect information. After some poking around, I found that my 4-pin ignition switch plug had a white wire with a red stripe that was hot when in both ACC & run positions. woohoo!

          fcm, you said "everything is common after the switch", does that mean I should've been able to connect my switch's above mentioned (white/red) wire to the wire the vehicle provides behind the head unit area as an ACC wire (the wire which is dead when my switch is in the ACC position), and have my in-dash clock light up, since "everything common" on that wire is given a live signal? I'm not having such luck, and no fuses blew when I did this and put my switch in ACC position. Does that mean my vehicle's ACC wire could be disconnected/broken somewhere between the fuse box, HU, and my in-dash clock?
          If you think that could be the case, having the clock work in ACC position isn't terribly important to me, all I really care about is my head unit. Since my head unit's constant +12v connection is still original and fuse protected, should I simply run a new wire from the switch's (white/red) lead to the ACC on my HU? I'm guessing you'd suggest I rig up a 10A fuse with this new connection?

          cheers on suggesting I test the switch's output, it was no different than testing a demultiplexor!


          • #6
            There should be two plugs off the ign. switch, [4pin to fuse box and 3pin to dash harness].

            Back feeding power, [connecting power to radio acc. lead] is not a good idea. 94


            • #7
              yeah, there were 2 plugs from my ignition switch; I didn't feel it was necessary to mention any wires from the 3-pin connector, since I didn't need to tinker with the signal going to my starter motor, or the incoming +12v from the battery. Not sure what the 3rd wire was, what are the chances of it being my ACC wire?


              • #8
                Have you checked for power at the radio acc. fuse with ign. in acc. and run?94


                • #9
                  no dice

                  Good idea to check that, fcm... my car has power at the 10A radio fuse in all ig. switch positions, including "off". i'm guessing that means the fuse controls the constant +12v lead to the head unit, not the ACC(removing this fuse resets my head unit's saved settings). what fuse would be hot only in ACC and run modes?

                  what is the possibility of my ACC wiring being somehow broken/disconnected someplace after where my ig. switch plugs into the under-dash fusebox, more specifically where it plugs into my clock and my radio? apparently the discontinuity is happening before the ACC wires branch off and go to their respective devices (the clock and the HU).
                  i'm calling it a discontinuity because there are no fuses blowing, so it doesn't appear to be a short. additionally, it doesn't appear to be a short because my in-dash clock works perfectly in run [II] mode.


                  • #10
                    Fuse 14 -15A, [hot at all times] in under dash fuse box is the constant power for the HU, fuse 22 - 10A, [hot in acc. and run] in under dash fuse box is the acc., [switched power] for the HU. 94


                    • #11
                      Originally posted by fcm View Post
                      fuse 22 - 10A, [hot in acc. and run] in under dash fuse box is the acc., [switched power] for the HU. 94
                      this is strange... in my car, the #22 10A "radio" fuse is hot at all times. i verified this by plugging my HU's ACC wire into the fuse recepticle. my HU then turned on, even in [O] mode. i'm now fairly confused... if my 10A radio fuse is hot at all times, why is my ACC lead in my radio wiring harness not getting any signal in ACC or "on"? same goes for my in-dash clock not turning on in ACC mode.


                      • #12
                        That is strange, are both fuse 22 and fuse 14 hot at all times?94


                        • #13
                          my fuse 22 is hot at all times, even with keys out of the ignition.
                          i'm guessing fuse 14 is hot at all times, because when i pulled it, my interior lights and clock went out (as they should). keep in mind my in-dash clock keeps good time and hasn't reset to 1:00 except for just now when i pulled the fuse. my ACC-related problem with my clock is that it doesn't light up when in ACC mode; it only lights up in "on" mode. Is is possible for the fuse box to go bad? i'm still stumped as to why my fuse #22 is hot at all times, yet my HU's ACC lead is dead at all ig. switch positions...

                          is there any single, specific wire coming from the fuse box that supplies ACC power? or, are there separate wires for the HU's ACC lead, and the clock's ACC lead?


                          • #14
                            Accessory power is supplied to the fuse box from the ign. switch, when switch is in the ACC. or RUN positions.

                            It's beginning to sound like something, [wiring] is pinned wrong.

                            Do me a favor, meter all the lead in the ign. harness, do the metering at the plugs, a 4pin and a 3pin, the 4pln is plugged into the fuse box and the 3pin is plugged into dash harness.

                            Give me wire color and what position the lead has power.

                            Should be...

                            White/black- 12V+ hot at all times .
                            Black/white- starter hot in start only.
                            Black/yellow- ignition hot in run and start.
                            Blue/white- 2nd ignition hot in run only.
                            Yellow- accessory hot in acc. and run only.

                            Maybe if we start at the beginning we can figure it out.94


                            • #15
                              my car has worked fine for the year or so that i've owned it untill the day my ACC problem happened; more specifically my HU has been able to turn on in "ACC" mode and "run" mode with the harness wired up to the provided ACC lead. i've never heard of vehicles changing their pins spontaneously

                              i'll get back about the ignition switch's outputs in a day or two when i've the time!