Starter Fuse Blowing

[Empty V]

I got the Q washed last weekend and when I went to drive it off the lot it wouldn't start. Instinct said it was the battery but I've got a kick-a** yellowtop so that was doubtful. After a few minutes I realized that the first thing that should be checked is the starter fuse. I pulled it and it looked fine but decided to swap. Voila the swap fixed it and I was off. Yesterday I went to an exhaust shop for a quote to have my down pipes re-done(because it's got leaks, clamps instead of welds, and the end pipes aren't symmetrical) and again the starter fuse blew. It's very odd because the fuse does look good but the contact points look slightly singed. I haven't tested for continuity but obviously there isn't any. Has anyone experienced this? Any ideas? I'm hoping it's not a short in the main wire harness. but I guess if it was, it would be easy to trace as long as I can find the correct wires. Thanks!

[Pwnin O'Brien]

Yeah, my guess would be a short in the harness somewhere. It's weird that it would happen after getting your car washed. Did you wash the engine or undercarriage? Was it a wash-it-yourself or was it a drive-thru car wash?

[Empty V]

Well it happened after the car wash and after lifting it up at an exhaust shop. I just tested the blown fuses for continuity and they've got it but for some reason the starter won't kick in with the one I replaced. The contact points are scorched though, I'll post pics shortly.

[Empty V]

So here's a pic of a new fuse and one that was burnt but still has continuity.

[ARKQX33V6]

What is amperage?

[Pwnin O'Brien]

What is amperage?

The unit of measure for electrical current.

[Empty V]

Are you asking what's the starter reading as far as amperage goes? How would I test that with a multi meter(still somewhat of a noob)? The fuse is a 7.5a and putting a 10a is too much resistance for it to start.

Thanks!

[ARKQX33V6]

The fuse is 7.5 A rating and is for the starter? The starter motor is a series wound DC motor and to start a cold QX4 draws about 150 A at 12-15 V, so what is the 7.5 A fuse protecting. It is usual for the starter motor to be non fused because of the heavy draw, so if your 7.5A fuse is blowing what actually is the fuse protecting, and fuses can only protect the wire they are not used to protect devices. A scratched up fuse connection link as you have shown in your picture will have very little to do with current draw. But the picture does not show the burnt out fuse link.

Fuses fail or protect for 2 reasons, over current and short circuits and these are the same except for the amount of time it takes for the fuse to pop.Remember that any fuse meets its threshold of protection at 80% of its rating so if your 7.5 A is blown the current that causes this is .8 x 7.5 or 6 A.

The starter motor is a big load and the solenoid to power it controls the starter motor and the solenoid power is quite substantial. I am curious what the 7.5 A fuse is protecting? Your fuse box should have a list named for each fuse.

[ARKQX33V6]

Be aware that the starter is inter-connected with the alarm, doors, inhibitor, it shuts down the starting circuit upon activation of the alarm. The 7.5 amp fuse may be part of the alarm, inhibitor. Can you describe its location?

[ARKQX33V6]

Empty V
If the 7.5 A fuse is blowing (the link melts) the fuse protects the theft warning relay and starter cut out. So check all the rubber boots at all doors and hood, they may be tilted.

Your fuse box is not sealed but liquid water could be splashing in by the seam, Duxseal would solve this possibility.

[Empty V]

Sorry for the looong delay in responding, I've got some more info. When I put it in neutral it starts right away. Also, sometimes I can pump the brakes and it will start. It doesn't do this every time but it does it. Is there some kind of trigger behind the brake pedal that is connected to the starter?

Thanks!

[Chuck Tribolet]

I am curious what the 7.5 A fuse is protecting? Your fuse box should have a list named for each fuse.

The starter fuse is protecting the wiring. Fuses protect wiring, not whatever the wiring goes to. The wiring it's protecting
goes to the starter solenoid, which closes some REALLY heavy-duty contacts that supply the 150 amps. The solenoid also
engages the little gear on the starter with the big gear on the flywheel.


Chuck

[Clurbear]

Hello! I'm having the same problem- my starter fuse blew and I had to push start the car. 14 weeks later- it has blown again!! 2 questions... WHERE is the starter fuse? And why is it blowing :(
Thank you