Blowing starter fuse

[01yellercobra]

I'm trying to help a buddy troubleshoot a no start condition. Everytime he turns the key it blows the fuse under the dash. He's looked through the harness and can't find anything rubbed through or obviously shorted out. So far the clutch switch and starter have been replaced. They were replaced before the blown fuse was discovered. Anyone been through this before? I'm scratching my head on this one.

 

[52merc]

Not much to go on to try and help. What car? What year? Which fuse blows? Does it blow in the ON position or the START position?

 

[*Jay*]

Sounds like something is shorted to ground, if he has a multi meter have him pull the fuse/battery and start checking the entire circuit to ground in all key positions.

To clarify, check the circuit of the fuse that blows.

 

[01yellercobra]

Not much to go on to try and help. What car? What year? Which fuse blows? Does it blow in the ON position or the START position?

Its posted in the Terminator section so you can safely assume it's a 2003 or 2004 Cobra. Which are the same car. It blows in the start position.

Sounds like something is shorted to ground, if he has a multi meter have him pull the fuse/battery and start checking the entire circuit to ground in all key positions.

To clarify, check the circuit of the fuse that blows.

Yeah. He just can't find the short. But I did some looking yesterday and found the radio and starter circuit are on the same fuse. I passed that info on to him.

 

[*Jay*]

Is he using a meter or just eyeballing everything??? Tell him to go around and reseat all connectors in the circuit and check the connectors as he goes. If he does have a meter have him also check circuits in the adjacent wires in any shared connectors.

 

[52merc]

Did you check the Starter Relay in the Battery Junction Box? A short between Pin 85 and 86 would cause fuse to blow.

 

[hotcobra03]

Any ants on fuse boxes?

Just dealt with a short issue on a f150

It’s time to shorten the circuit to locate section of harness short is in

There are connections along circuit that can be unplugged along testing

Chilton Library


Here is a link with full wiring diagrams and location pictures of connections

 

[52merc]

OP, did you get your friend's car started?

 

[01yellercobra]

Is he using a meter or just eyeballing everything??? Tell him to go around and reseat all connectors in the circuit and check the connectors as he goes. If he does have a meter have him also check circuits in the adjacent wires in any shared connectors.

He's using a meter.

Did you check the Starter Relay in the Battery Junction Box? A short between Pin 85 and 86 would cause fuse to blow.

He swapped it with one of the others I believe. No change.

Any ants on fuse boxes?

Just dealt with a short issue on a f150

It’s time to shorten the circuit to locate section of harness short is in

There are connections along circuit that can be unplugged along testing

Chilton Library


Here is a link with full wiring diagrams and location pictures of connections

Ants? Not that I know of. He drove it to the store, shut it off and went inside. When he went to leave he turned the key and nothing.

OP, did you get your friend's car started?

Not yet. He went on a trip that he didn't tell me about. And this week I'm in Hawaii with thr family. So this upcoming weekend I might be able to poke around on it.

 

[52merc]

That whole circuit is pretty simple. Between the Central Junction Box Fuse-6 and the Clutch Pedal Position Switch there is a branch circuit at S239. If the fuse blows when you go to START and the clutch is NOT depressed, this means that the short is somewhere between the CJB, the Clutch Pedal Position Switch, and the radio. From S239 power goes to MACH1000 Head Unit Pin-3 (Red/Lt Blue wire). I would be checking this wire out to make sure it hasn't got pinched under the dash somewhere.

If the fuse blows only when you push the clutch in, then the problem is after the CPPS. I would then pull the Starter Relay from the BJB. If the fuse blows again when you push the clutch in, then the short is somewhere between the CPPS and the BJB. If it doesn't blow the fuse, then the problem is between the BJB and the starter.

This should help you isolate the short. Hope this helps you out when you get back to working on the car after your vacation.

 

[01yellercobra]

My buddy ended up losing patience and towed the car to the dealer. He did end up finding the short was between the CSS and fuse box. I guess it was a wire in the harness they ended up repairing the wire and it's all good now.

 

[52merc]

Great. Glad he got it fixed and thanks for letting us know.

 

[01yellercobra]

No problem. The thought is the harness got nicked when the engine was being pulled or putting it back in.