rotordave

iTrader: (1)

G'day,

Before I start - I have an Australian production '82, and first owner had an alarm installed. Who knows what dodgy things the electrician did when wiring that up, but I find it difficult to believe he would have left it in a state where half the interior electrics don't work.

I have a short somewhere on the 15 amp "clock" fuse - the constant power circuit. I've done lots of searching but the cause of shorts seem to be too varied for that to be a great help.

I have isolated it as much as possible. This is what I know:

I have disconnected the following in an effort to stop the fuse blowing: Clock, Luggage Compartment Light, Interior and Spot Light (map/dome light), Oscillator, Ignition Switch Light, Seat Belt switch (at X-11 - although the wiring harness forward of this connector does not have the wiring for the seat belt switch). The cigarette lighter is on a different circuit on Australian 81-83's. The fuse still blowed with these things disconnected.

Everything on the other circuits the CPU is on works correctly - hazards, wipers etc. Its only the things on this clock fuse circuit that are broken.

Critically, I have found that with the CPU disconnected, the fuse does not blow. Looking at the wiring diagram, this would suggest that the short *cannot* be between the fuse and the X-16 CPU connector. And how likely is it that the short is occurring in the CPU itself? If the other functions of the CPU work, I'd think it unlikely. Anyway, I've attached a picture from the 82 wiring diagram showing what I've disconnected on that circuit to isolate the short.

I have a basic understanding of electronics, but I cant figure this one out. One thing I know is that, for much of the circuit, a grounding would just result in things not working - not a fuse blowing - the door switch wires for example. Its next to impossible for me to look along the wiring harness for a shorted wire, there has to be a better way. I'm thinking that if I somehow test each wire that is going into the CPU for continuity or whatever that I would be able to isolate where the short is. I really want to get that circuit working!

I'd really appreciate any advice.

Cheers.

rotordave

iTrader: (1)

So, no one has any advice or opinions?

I'm thinking about trying a different CPU.

lfd75

Are you sure the lighter is on on a different circuit? I had the same problem and it turned out to be the lighter being totally corroded (though in Canadian 81-83's the constant power wire also provides power to the lighter). you may want to also check the radio (I'm pretty sure the presets are on the constant power wire)

rotordave

iTrader: (1)

Yes I'm sure. It has a seperate fuse and besides, it works

RX-7 Chris

iTrader: (19)

I have a similar problem with mine. Although my fuse does not blow, they just don't work. Every time I have messed with it I keep coming back to the CPU. I would look at that first.

gsl-se addict

iTrader: (3)

I would say that it is the CPU. At least try swapping it out. There are two separate circuits feeding the CPU. One on switched ignition (wipers and such) and one on constant power (the circuit that you are having problems with). Here is a diagram of the '84 CPU that I uploaded quite awhile back. The '82 is very similar.



By unplugging the CPU and the fuse not blowing, you have found that the short is in the CPU itself or somewhere downstream of the CPU. You know things like the wipers and turn signals work, so those can be ruled out. If the new CPU doesn't fix it, I'll help you to figure out what to do next..but you are on the right track and are doing everything correctly.

Is the alarm still connected? Could it be possible that they connected it to the door switches to detect the door being open with the alarm armed? Perhaps if the CPU doesn't fix it, maybe disconnect the alarm or trace the wires for the alarm and see if it is tied into the door switch or any other wiring that might be connected to the CPU.

Good luck.

Kent

rotordave

iTrader: (1)

Onya Kent, those are the same conclusions I had come to. I'll try another CPU anyway - even then, I can't be sure this one I have to try is working!

The thing about the short being downstream of the CPU... by looking at the wiring diagram you can see that any short downstream of the CPU would only mean that a device wouldn't work - that it would be grounded. For example, the door switch - if it grounds by short circuiting, it doesn't matter - it will simply translate into a "door open" signal. It wouldn't result in a blown fuse. This is the thinking that lead me to the conclusion that the CPU is bad.

I wish the diagram of the 82 CPU was as detailed as the 84.

Thanks for your replies.

bliffle

That's a tough one.

If you get REALLY desparate, give this a thought: while it's hard to track down a short in a DC circuit, it's easier with an AC circuit because you can use a signal injector and a signal detector. So maybe it would help to use an injector and detector like the telephone guys use (they're about $30 each at electronics stores). Then you could try disconnecting the negative post of the battery and tracing out circuits (a lot of work), and you could also try it with the DC applied in order to work past relays.

Sounds like a lot of work, though.

rotordave

iTrader: (1)

It was the CPU! I tried another one and it all started working!

The headlight reminder chime makes me laugh, its very japanese I'm sure it will **** me off after a while.

Finally I can have interior lights! The ignition light doesn't seem to work though...

Thanks for your replies.

gsl-se addict

iTrader: (3)

Good deal. The ignition light is supposed to come on when you lift the driver outer doorhandle. It is supposed to come on for about 6 seconds or so. Might be a bad swicth in the handle or the light itself is burned out or disconnected.

rotordave

iTrader: (1)

Seems I spoke too soon ...

CPU works alright, but there is a bad connection somewhere on the door switch circuit because now when I drive along (and sometimes just sitting there), the interior light and hatch light flash randomly, despite the doors being firmly closed.

A side effect is that the alarm comes on randomly, thinking that the doors have been opened.

When the alarm comes on, it flashes the parking/running lights on and off, and the headlight reminder chime gave up the ghost not long afterwards - I think it didn't like being turned off and on so much or something. Hasn't worked since yesterday.

I'm thinking that if something is arcing, maybe thats what killed the original CPU in the first place...

rotordave

iTrader: (1)

OK... the chime has started working again... :O And the ignition light *does* work.

And the flashing interior lights/bad connection... The way they wired up the alarm, the switch they added for the hood opening is wired into the same circuit... ie, if you open the hood, the interior lights come on!

Maybe it was bouncing on and off with the vibration of the engine, so I've disconnected that switch and will see what happens now...

rotordave

iTrader: (1)

Disconnecting the hood switch doesn't do anything while driving it, the lights still flash driving over bumps...