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Discussion Starter #1
I'm at a loss and hope someone here may have encountered the same problem.

The problem:

Sub tank light is on on the readout ( and sub won't work).
With keys out of ignition the heater fan will still run, air con switch glows very faintly, intercooler fan that is wired into run circuit is constantly running, can hear heater fan (blower relay) cutting in and out.
No radio or ariel working though unless keys are on accessories.

What I've done so far:

Checked earth straps from battery to body, battery to motor and motor to chasis.
Changed relays around.
Checked all wiring from sub tank fuel pump.
Disconnected battery for 1/2 hour, which fixed the sub problem the first time, but not this time.
Had a sticky under the dash looking for bare wires.
Checked all fuses for melt down.

Someone please help.
The main battery drains over night and if it wasn't for the second battery the car would be unuseable.
 

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The first thing I was thinking while reading your post was, earth problem.

But seeing that you have already looked into this I guess not.

So the next things I would suggest, (seeing that all the items you have mentioned are ignition fed).

Try disconnecting the small plug at the alternator.

You can also try disconnecting anything that you may have connected into the ignition circuit, such as the intercooler fan.

Hope this helps.
 

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Discussion Starter #4
Just went out and disconnected the plug in the side of the alternator, also the intercooler fan.
No luck, still have the heater fan running with these disconnected.
I also tried the windows with the keys out of ignition and they don't work with the ignition off, neither do the wipers.

Nothing recently installed Matt. This problem occured without my help.
 

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The Bear
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Check the plug on the ECU, make sure it is firmly attached to the ECU, maybe unplug it and reinsert it after a minute or so, whoops just looked above 4.2 old tech, must be a crook relay, check the relay box near the battery for a faulty one in there. If those fans are running then it might be a faulty relay in the ignition circuit somewhere, trouble is Nissan put the dam realys everywhere under the dash as well, might be a faulty ignition barrel sw too, crap across terminals in there, or a bit of solder broken off and shorting across. a Multimeter or test light would be a good friend to use for tracing power path. thats where I would start, dunno otherwise. Thats what sparkeys are for......
 

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Discussion Starter #7
allananicol - spot on.
The relay that was put on for the intercooler fan was taking power off the glow solinoid. Why? I have no idea.
Anyway, the soliniod destroyed the resistor in the relay and was back feeding through part of the ignition circuit.
New relay powered off the main battery and all's good again.
Even the sub tank is working again.
 

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Check the plug on the ECU, make sure it is firmly attached to the ECU, maybe unplug it and reinsert it after a minute or so, whoops just looked above 4.2 old tech, must be a crook relay, check the relay box near the battery for a faulty one in there. If those fans are running then it might be a faulty relay in the ignition circuit somewhere, trouble is Nissan put the dam realys everywhere under the dash as well, might be a faulty ignition barrel sw too, crap across terminals in there, or a bit of solder broken off and shorting across. a Multimeter or test light would be a good friend to use for tracing power path. thats where I would start, dunno otherwise. Thats what sparkeys are for......
Just a bit of Pub Ammo, The later 4.2's, I believe series III onwards (Factory Intercooled jobbies) have a basic form of computer, my GUIII wagon had one, so does a mates GUII Ute both Intercooled 4.2's

(controls the advance/retard solenoid for the timing etc, the reason i know is his computer failed and we trial and error traced it back to the timing solenoid.)
I believe its quite a basic ECU, but an ECU all the same.

Cheers, Dean.
 

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Discussion Starter #9
Just another update.
It's back again. This time same as above but with a couple of extras.

Occasionally feedback through left rear door speaker.
Blown dash fuse twice so far and also the aircon fuse once.

All ideas appreciated.
 

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The Bear
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Did you get a solution to this, bet it was in the fusable link/relay panel next to the battery, or back to the common thing, faulty glow plug relay/or timer.
 

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Although I can't think of anything other than start isolating circuits and testing individually for shorts and current draws.

On the other hand it could be worse, you could own a jeep and it could turn into a mobile BBQ!
 

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Discussion Starter #14
Problem found.
After months of looking for this problem I finally bit the bullet and took it to an auto lecky.

Where the wiring harness runs along the passenger side of the car was the culprit.
At some stage it has been crushed under the door sill and bared a few wires.
Add to this a water leak into the same area and all hell broke loose. Dam lucky it didn't go up in smoke!

Part 2 is now going to be to find the water leak.
Any ideas?
 

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I'd looking at:

  • windscreen seals
  • plenum
  • leaks through fire wall (aftermarket cabling, missing grommet etc)
  • air con hose dripping in the car rather than outside
 
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