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Forester 2000 - immobiliser fuse


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Hi, I am new to the forum. I am searching for clues about a strange intermittent electrical fault in our 2000 Forester (Australian model, 2.0 litre). The fuse SBF5 (30A) keeps blowing intermittently. Unfortunately this fuse is for the immobiliser, so once it blows the car won't start. A Subaru mechanic recommended that I unplug the tow bar electrics, which I have done, but fuse continues to blow. The fuse is also shared by the reversing lights, indicators etc.

 

We can't narrow the event down to any particular circumstances, except perhaps wind direction and the phase of the moon. Twice we've had the car towed to the auto-electrician, and each time he's replace the fuse and the car has driven perfectly for him.

 

Does anyone know whether this is a known bug in this model Forester? Any help of advice would be appreciated.

 

 

Dean

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If this were my car I would ask the service department for a copy of the wiring diagrams that cover the areas that fuse supplies power to. I would then replace the fuse with a headlight tied to some jumper leads and start tapping on suspected areas of trouble when you hit on the short the light should turn on or get brighter.

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Thanks Glen,

 

Would the headlight need to be a particular rating? - 30A is a big fuse.

 

My assumption is that something is shorting while driving the car, but the car can keep running, the immobiliser only causing a problem once the engine is turned off and I attempt to restart.

 

Dean

 

If this were my car I would ask the service department for a copy of the wiring diagrams that cover the areas that fuse supplies power to. I would then replace the fuse with a headlight tied to some jumper leads and start tapping on suspected areas of trouble when you hit on the short the light should turn on or get brighter.
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Yes your right about the current, but most likely the normal flow will be significantly less. Depending what is normally on will determine how much the light glows. You could use a high beam which will give more draw or parallel a couple of them if needed. Since the indicators are part of the system hopefully this problem is not in the steering column somewhere. It is a good suspect though in my opinion.

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Get a 30 amp auto circuit breaker and as many fuse holders as you have subcircuits. Run a wire cluster from the breaker with an individual fuse for each circuit. You have to carefully calculate the load on each circuit and fuse it correctly. Dirive car until one fuse blows. Usually on a bumpy road.

Now you only have one circuit to trace.

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Thanks all for your suggestions. Happy to report that the problem was tracked down by the auto electrician after being towed to him for the second time. Very generous of him considering most places are closed btw Christmas and New Year. He found that a wire that leads to one of the exhaust monitoring devices had come away from it's clip and had chaffed against the right CV Joint. Explains why the problem happened sometimes when car was reversing, since the CV axle rotation in the other direction would cause the chaffed wire to short out. The exhaust circuit is connected to the engine control unit and thus the immobiliser. We use the car offroad sometimes so maybe the wire snagged on something at some stage.

 

Thanks again.

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