Tz779

Honda peeps,
I took on the job of replacing the head gasket on my daughters 2001 civic, and while disconnecting the wire to the power terminal of the alternator, there was a spark. Yes, I forgot to take ground battery ��. Now, everything reassembled, oil changed, new coolant, I have no power to anything. The battery is new, showing 12v, but not even interior lights or door buzzer comes on. I have 12v at the fuse box under the hood, but no power to the live terminal of the alternator, key fully turned on. Where do I start? 40 amp fuse for alt is ok. Checked and cleaned ground wire. Thanks so much!
Robin

ezone

Open the fusebox lid, find the biggest fuse in the thing (probably 80 amp). Look through the little window and see that it is blown. Replace.

Check all the rest too.

Tz779

ok, checked all fuses under hood. fuse 20, 40amp, Ignition 1 does not show 12v with key on. But multimeter says fuse is not blown/broken. no voltage at alternator. Thanks!
Robin

CraigW

iTrader: (1)

No voltage a main lead from battery ?? I only show the 80A as protection.

ezone

You didn't check the 80A fuse?

Tz779

yes, it is ok, voltage on both sides of terminals
fuse #4, 10amp alternator, under steering column is ok

ezone

Do you have B+ at the terminal marked BAT?
Do you have B+ at the terminal marked ALT?

Tz779

ummm, B+? Is that voltage (battery positive?)? i'll check, ive only checked 18 and 19, no current across 19, but multimeter shows continuity(?)
thanks! ; )

ezone

B+ is always battery positive , or 12v

Test using meter set on volts for live circuits, not ohms.

Tz779

Oh, yes, thank you, though. I had battery disconnected to see if I had continuity across 40 and 80 amp fuses. When I hooked up battery, test light lit on 80 amp, but not 40 amp, with key on.

Just got home from work, I'll check in the morning. Thank you for your help! Very appreciated!
Warm regards,
Robin

ezone

So then the 40A is blown?

Tz779

Possibly, but it shows continuity with an ohm meter, and the thinner wire at the top of fuse is still intact, not separated.

So, I unscrewed the 40 amp fuse from fuse block and checked with ohm meter, yes, shows continuity, fuse ok. Installed back in fuse block, battery hooked up, no voltage across the terminals of the 40 amp fuse!?
Robin

ezone

Are you using the meter incorrectly?

Meter neg (black) lead attached to neg post of the battery and leave it there.
Probe spots in the fusebox for voltage (B+) using the single positive (red) lead of the meter.

Same if you were using a test light, clip its wire to the neg battery post then probe for power with the sharp end

Tz779

Yes, that's how I am testing for voltage. I dropped the multimeter and broke it, so resorted to a test light, as you described. New meter tomorrow!

Tony Alva? That is a valuable skateboard!
Robin

Tz779

ezone,


I replaced 40 amp fuse.

I have B+ at terminal marked BAT
I DO NOT have B+ at terminal marked ALT

Does that suggest the problem is between battery and the fuse box?

Best,
Robin

ezone

The 80A fuse is blown.

Tz779

ezone,

YES IT WAS!

i am sure i checked that fuse, in place in the fuse box and read continuity with my multimeter. i took the fuse out, checked it again, blown.

Thanks so much. I am done with multimeters from Craftsman (Crapsman now), Pep Boys (Innova 3320 that always reads 12,60 volts). I will buy a Fluke when I have some $$.

Now i have to deal with a leak in radiator!

Best,
Robin

ezone

But this could have been found with the $3 test light LOL

Tz779

yes i was using my test light, which told me i had no power to that BAT terminal. still, the Innova multimeter i bought the other day ALWAYS reads 12.6 volts. Always. i dont trust it...

CraigW

iTrader: (1)

Inherent problem with digital meters is the high impedance that puts no load on the circuit.
Good in some cases......bad in others. Your 12V test light provides a good load.

If it reads 12.6 with the leads disconnected.... then it's done.

ezone

If he attached one meter lead to each side of the fuse and read battery voltage, then he's not understanding what he saw. (voltage drop test)
If the fuse was good there would be zero volts showing.
An open fuse would show battery voltage.

Tz779

i was reading resistance (ohms) across the fuse. (she!)

CraigW

iTrader: (1)

^^^ On what scale ?? You would likely only use the lowest (200) setting, and look for 0 Ohms if fuse o.k.

Hope you had a battery terminal disconnected when in resistance function.