so long story short, my alternator died and due to weather and my busy schedule i had to pay a shop to put in a new one. they put in a new one and when i got the car bak (had to wait for new ecu sincce mine got fried) the fue for the alternaotr and speed sensor keep on blowing almost instantly one the car is ON. with jus the key foward in the 2nd position, it doesnt. i figured it was a short in my wiring harness so i pulled the IM and checked all the wire and covered them all. crazy thing is, when the car is on, the fuse slot is reading 12V jus like its supposed to. speed sensor is reading 4V just like its supposed to and power for alternator is reading 12V like its supposed to. i figure there has to be a short somewhere but i have no idea where to look... how can the fuse be blowing if the fuse box is reading 12V?

****the fuse box reads 12V with the key in 2nd position and when car is on.... why does the car have to be on for the fuse to blow??

plz any guidance is highly recommended for this is the first time ive had to mess with electrical wiriing. i didnt even know how to use the damn Volt meter at first lol

 

I bet you have a 96+ civic,,, I had the same problem,, its the wiring harness hitting against the intake manifold somewhere and shorting out.. when i push my wiring harness down, away from the manifold, my fuse would last a bit longer, lol I guess until it hits the manifold and shorts it out again...

 

Your voltages are fine. The fuses don't blow b/c there's no voltage there, they blow b/c of an increase in current (i.e. shorting to ground).

Check your wiring for that circuit.

Get a multimeter and ohm out each wire from one end to the other (not sure how easy this will be) and see if your getting 0 ohms or OL (open loop, meaning infinite resistance). 0 ohms and OL are two completely different things.

 

yes its a 00 civic, and i already did the manifold bracket thing.. didnt help. i wrapped all the wires in that plastics wiring wrap.. no help. ??

 

bump to the top desperately need help!!!!

 

i had the same problem, mine was in the two blue and gray connectors down below the IM. these are ground connectors

also check the plugs inside the speed sensor and the alternator they could be corroded and could be broken off

 

This comes up every now and then; if you already checked the wiring at the intake manifold bracket, then check your O2 sensor wiring. Usually, the O2 sensor wiring has lost some of the insulation (or was spliced and butt connectors used) and is touching the chassis, causing the short.

 

very good point. i forgot about this. this exact thing happened on my brother's car, it was strange because it only happened when it would go into fifth gear because his o2 wires were hanging on the shift linkage and every time he went to fifth it would short causing the CEL to come on and the alt/spd fuse would blow

 

does it make a diff. as far as me having 02 sensor disabled?? im boosted. but i am having a problem with my shift linkage hitting exhaust....?

 

same thing is happening to my car right now.....sooooo confused!!

 

yes it absolutely does because one of the wires still have b+ power in it even though it's disabled the ecu just doesn't read it

 

thanks you all the 02 sensor ended up being the problem, gonna go get a tool today and jus pull it out and put a plug in it. thanks