Front Parking Light

[justin.graeff]

So, I've got a question about my turn signals. I was going through my fuses yesterday and I noticed a few were switched around. (i.e. there were wrong fuses in spots.) One of them was the right directional light/engine room light. I noticed there was a 30 amp fuse in there when there should be a 10 amp fuse. So, I went to Radio Shack and bought some new fuses and fitted a 10 amp fuse in there. I turned on my parking lights and pop, there went the fuse. I looked back at the 30 amp fuse that was in there and saw that the plastic was really melted and the metal was hot. I popped the fuse back in and turned on the parking lights again. This time the right parking light came on very dimly and the fuse got real hot. I took it out and left it out.

Why would it pop like that? The blinker works fine but if I turn on the parking lights, it will just pop the fuse. There is not even a light in the engine bay, as in the bulb isn't present. Is that the problem? I wouldn't think so.

Sorry for my never ending posts. I have a lot of problems with my poor Saab that I want to fix. I can never seem to find all the answers.

On the brighter side, kind of. In the post involving my clutch smell, I figured out it was just oil leaking somewhere. I think it happened when I put too much oil in. My check oil level light came on and I assumed that when it came on, it must be pretty low, so I put in two quarts. Apparently that's not the case.

[Cliche`]

You've got a short somewhere. Break out the voltmeter and start searching.

[Thirsty9000]

I've seen 9k's to get rather furious about being a half quart low on oil. They don't like to be abused. If you do abuse them, they have no qualms about taking a bite from your a**. They always aim for the wallet side and rarely miss!

[justin.graeff]

So you're telling me I have to trace my wires again? It's hard to do that in the car. Every wire is bundled with every other wire and it's impossible! There are so many things wrong with that car and I just don't know what to do. One day she'll be perfect. I am waiting for that day.

[djtaylor]

Originally Posted by justin.graeff

So you're telling me I have to trace my wires again? It's hard to do that in the car. Every wire is bundled with every other wire and it's impossible! There are so many things wrong with that car and I just don't know what to do. One day she'll be perfect. I am waiting for that day.

I don't wish to sound flippant but unless you're prepared to trace the wiring, how else do you think the problem is going to get resolved?! Just changing fuses or bulbs certainly won't do it.

Yes it's hard but then again, you can't change the timing chain and sprockets by just removing the oil filler cap and pouring the bits in, you have to put some time and effort in i'm afraid.

Impossible isn't really a word that works when it comes to straight electrical faults. Electricity can't flow unless there's a complete path and by the description you've given, there's indeed a short or partial short circuit somewhere.

Judging from your posts, your strong point isn't electrical which is ok but here's the good news, you need to apply logic, pure logic, remember nothing can flow without a path so you just need help in knowing where to start.

Firstly, obtain a wiring diagram. If you don't have one, everything else will be largely pointless. Yes you can do this stuff without one but it just becomes much harder.

On the wiring diagram, choose a point to start, it doesn't really matter if you start at the battery or at the bulb or at the fuse as long as you have a logical progression through the circuit.

Without going into too much detail because that would be overload, bear in mind that with all the lighting, you effectively have two circuits after the switch so the general rule of troubleshooting is to halve the problem.

Work on one side at a time, check continuity (electrical resistance between points in a circuit) and then check continuity to the switch etc.

If you have a short circuit, DON'T connect it up! Fuses are designed to blow before the wiring but fitting larger and larger fuses means that a current will flow that the cable wasn't designed to carry and in simple terms that will result in the cable overheating, frequently glowing red, burning out and setting fire to the car - it's that simple! Car batteries hold a huge amount of energy and if you want to give this a go, get a nice 5 amp rated cable and short it across the battery (out of the car, just in case the battery objects and explodes). The cable won't last long, a few seconds maybe.

So take this very simplified diagram of a lighting circuit:-



To save wiring, the car body provides one return path, the negative ground so everything will have a path there. Start by removing the bulbs, you don't need them in to trace continuity and they'll only confuse when seeking a short circuit anyway.

Start by disconnecting the battery or at least remove the fuse, you don't want to accidentally provide 12V to a meter measuring resistance. They tend to go pop or blow an internal fuse.

At the bulb terminals, measure the resistance between the terminals and car chassis. If there's a short circuit, you'll find that the resistance is fairly near to zero. Remember that one of them *should* be connected to ground anyway, but the other one shouldn't be. So test at TP2 and TP3 (test point).

Because the wiring connects between left and right, you won't know one which side your short is at this point, so you're going to have to go somewhere along the cable to split the circuits. Half way is a great point but it's also going to depend on where you can get to this with cable access. This is where your wiring diagram will come in because you'll be tracing the wiring colours and just for fun, sometimes they can change along the route

With the circuit split, you should find that one side grounds when it shouldn't and the other side doesn't. You then need to repeat the exercise on the faulty side, choose a point half way along and see which half has the fault until you find it.

To be honest, when it's a short circuit, usual culprit areas are where cables pass through the chassis, they get trapped, someone pinches a cable when putting something back and it chaffes and shorts. A cable running as part of a loom generally won't short for no reason.

TP1 on my diagram is simply to test that with the lighting part downstream from the switch, you should be able to measure 12V here without blowing the fuse, if with the lighting circuit disconnected from the switch, the fuse blows then your problem is upstream from there but judging from the description it doesn't sound like it.

Apologies if this sounds noddy of you knew this already but it's hard to gauge from an internet forum, what someones skill level in a particular area. FWIW, my background is electronic engineering and I get no pleasure in troubleshooting car wiring, it does frustrating things like earthing through components that you wouldn't suspect and gives daft results. I'm sure you've seen tail lights where someone brakes and the indicator and reversing light come on and flash instead? Typical earth fault but just a mare to find, other than cleaning all the bulb contacts in sight.

You will need that wiring diagram though.

David.

[justin.graeff]

You make it sound so easy when you put on paper, err, the internet. Anyway, where can I get a wiring diagram? I think I have been going about my shorting problem all wrong. I never had a diagram and after your explanation, it sounds like I really need some.