Civic-EG.com Forum 3.3.1

- Sun Sep 16, 2012 2:42 am #315760 Car: 94 Civic Si
-Problem: When cranking engine its seems slower than normal and the speedometer needle moves as high as 100mph
-Brand new battery
-Batt voltage: 12.63
-Volts tested while cranking: 8.90
-Volts tested at Blk/Wht wire disconnected from starter cut relay when in start position:12.5 (Yellow arrow in pic)
-Parastic drain test: 15 milliamps
-Electrical add on: 2 way paging alarm
-If my car sits for more than 12 hours the car will not crank at all. Batt volts will be under 11.6
-Hypothesis: I'm thinking there is a short between the Blk/Red wire after the starter relay cut and the starter solenoid. (Red arrows in pic)



I did the test when I hot wired the starter solenoid directly from the battery and the motor cranked normal. When I use the key to crank it will seem slower than normal.

Is there a easier way to find a short without taking a lot of things out?

If you got any questions just ask

94' civic si
JDM B16A w/AC
My daily driver: http://tiny.cc/3bdut

K3 GSXR 1000: http://tinyurl.com/3u6obdx

[suspendedHatch]

- Sun Sep 16, 2012 3:46 am #315762 Any time there is an electrical problem, everyone says "short". What is an electrical "short"?

If you connect the battery positive to the battery negative, the wire will get hot because a lot of current is flowing unhindered. A smile wire will burn pretty quickly. If you fuse this wire, the fuse will blow immediately, no electricity will flow, and the wire will survive. If you have a very very thick gauge wire, and a very very high amp fuse, the wire wont burn and the fuse wont blow. Instead the battery will get hot and explode.

These are all the scenarios for a short. Most commonly, a fuse will blow and something will stop working. If the rating on the fuse is too high for the wire, then the wire will catch fire and possibly set your car on fire. If you added a 00 AWG amp wire and it is shorted out, most likely your car will catch fire. In rarer cases the battery will explode, usually resulting again in a car fire.

As you've noticed, shorts tend to be very obvious. They are rarely the cause of the electrical gremlins they are attributed to. All that "short" means is that battery power has taken a shortcut directly back to battery negative without having gone through a relay, resistor, or electrical device that impedes its flow. While the starter can handle 100A of current (and brief spikes even higher than that), most circuits in the car are about 10A. Just look at your fuses. 5, 10, 15, 20, a couple 30. Under the hood there is a 60, 80, for things like headlights. A short means there is no resistance so the full force of the battery - something like 100A like the starter gets - is going through your 15A wire.

You find a short by testing a power wire for resistance or continuity to ground. It should have very high resistance. You keep moving down the circuit until you find continuity. That happy little screw through your wire or that sharp piece of sheet metal that pierced the insulation. Or some idiot's tampering...

15mA is very low and totally acceptable amount of current drain. It's possible for a brand new battery to go bad (impact, or allowed to go flat for too long), but that doesn't seem to be the case here. You said you hooked up the starter directly and it cranked just fine. This indicates that the battery positive, the starter wire, or the ring terminal connection on the starter should be checked. I think you are indicating that you jumped the starter solenoid as well instead of hooking up the starter and turning the key, this would indicate that the starter solenoid is bad, though people rarely replace this independently of replacing the entire starter.

Sorry for the novel, but I type like a madman. And I plan on using this for an article.