Bill Ball

On a buddy's 87 I found his non-working radio was due to no ignition switched power at the radio. This power comes from the ignition switch through a noise suppressor directly to the radio. I found that the wire from the ignition to the suppressor was shorted to a bracket under the console near the suppressor- somebody had pinched the wire under the bracket when screwing it back on. I suppose I could wire this into another switched power source, but I'd like to restore the source from the ignition but it's dead. I've highlighted it in RED in this small section of the wiring diagram. I don't quite understand how to read the switch paths back to the power source. I see some 30s - those are not fused, of course. So, did this short cause another short in an unfused power source to the ignition switch? Everything else seems to work fine. Help!

BTW, the coordinates that the diagram says this wire goes to are wrong, they are H65, A66, M62 (60s not 40s), but I'm not interested in that. I want to know the power source.

Mrmerlin

Bill have a look under the side console next to the passenger side seat IIRC there is a supressor in there

VehiGAZ

My radio is wired into the interior lighting circuit (fuse 23? 24? something like that).

Is that correct? I pull the lighting fuse when working on the car with the doors open for extended periods, and I'd prefer not to reprogram the HU every time.

Bill Ball

Stan, you are reading too fast. I already traced it to the suppressor. The problem is the wire going from the ignition switch to the suppressor. It was shorted and is now dead.

Bill Ball

Uh, no. The radio should get its own constant power through fuse 22. The same harness plug that provides ground and switched power to the radio provides the contant power through fuse 22. They should have used that instead of wiring to another circuit. You might find this harness plug behind the radio. It has 2 red wires and one brown. One of the red wires is ignition switched and the other is constant power from fuse 22. You can use a voltmeter to figure that out and rewire your radio.

Hey, wait a minute - I thought I was the one that needed help here!

Mrmerlin

OK sorry Bill , to answer your question i dont how to read the switch positions maybe Alan does. in the meantime,
might you have another ig switch to test as the switch could have internally melted.

VehiGAZ

Thanks Bill. It's supposed to be #22 on an '89 as well. Some remnants of the original wiring are still there, so I will see if I can find the proper circuit and re-wire. I had go back in anyway to re-ground the radio since I have a mild alternator whine.

borland

Bill,

The stereo head unit's +12V (Ignition) wire is a signal wire only, so very little current will flow through that wire. That's why there is no fuse on that wire (directly from the battery to the ignition switch). The radio turns on when it senses power from the ignition switch.

The radio gets power from the +12V (Constant) wire.

Bill Ball

So, do you figure, like Stan, that this short probably burned out the contact in the ignition switch? The rest of the switch works fine. I need to return the car tomorrow and don't have a spare switch, so I guess I'll find another switched power source nearby and run it to the suppressor.

borland

That will work, however it won't work like it was designed.

The ignition switch has a special function of being able to turn on the stereo without other accessories being on at the same time. If you turn the key only slightly, the stereo powers on, further turning the key and the other accessories power on too.

borland

Also the ignition switch is designed to deactivate the stereo during starter motor cranking.

Bill Ball

Borland: Oh, yes, thanks for reminding me about that. Argh. That particular output of the ignition switch goes just to the radio. Well, some other 15 bus output will have to do for now.

Alan

No totally incorrect. On all years the switched supply should be as Bill shows From the R (Radio) terminal on ignition switch via an inductive supressor.

Alan

Alan

Actually that is not intended functionality - it may be true on some switches - but by detent position the function of X & R is the same. If you look at the 93/2 Ignition switch schematic you will see something different between X & R - however I think this is a mistake - my car shouid have this switch - but it behaves like all others...

Bill an alternate for R is X if you need to swap temporarily.

I'd suspect that the wire from R is more likely burned out somewhere between switch & supressor rather than the switch coontact itself - unless you tested the switch output directly?

All the power for the switch comes from the ganged permanent 30 connections to the battery - easy to test at the switch with a probe on R. With switch out checking the resistance between R & 30 may tell you if you have a problem but this could be a confusing measurement too... The 30 supply to the switch is fine - if that fails you have nothing anywhere...

Alan

Pcplod

So what does a current owner do to rewire the HU in correctly when the PO has the wiring totally screwed up but the original wires are still present?? I don't follow where the signal wire hooks into an aftermarket HU if the 12V are coming from the other wire. Please forgive my questions if they seem dumb, I am just trying to figure this out so that I can make mine right.