Fusebox blues

Unfortunately, this evening it's storming. The tornado sirens went off once already, chasing us all to the basement. I think the authorities were a little trigger happy with the tornado warning, but... If it clears out I may be able to go out and do a little sleuthing. We should have almost 3 hours of daylight left, but right now it's dark enough to use the headlights. drat.
Maybe I'm a little dense. I don't see fuse "H" on the schematic. It looks like it uses fuses "M" "B" and "A"
 
Okey Dokey

I checked fuse A and I have 12V across that one, but nothing across any of the other ones with the ignition on and the blinkers off. The grounds next to the steering wheel look clean and solid. I took each one off and on several times to clear any corrosion. The hazard lights work, but I don't get any voltage across any fuse except A when they are on. What next?
 
What?????

How could voltage going through a fuse mean it's blown?:shock:
So I go out and take fuse A out and the little metal thingy falls apart in my hand. I replaced it with the 8A fuse from position H and the turn signals blink like a mother-.... well you know what I mean. AND the blower blows. I'm so confused now, I have to have a sit down on the porch with an adult beverage. I'm ordering all new fuses immediately, if I can find them.
 
No worries. European fuses

are easily found at your local Autozone. I emailed you a good schematic. Sorry it's late!
 
Checking for potenial or voltage.

A volt meter gives indication of difference of potenial or voltage.

When trouble shooting electrical circuits the normal method is to find a reference to difference of potenial. On a car this is normally the chassis which is ground or negitive potenial of the car's battery. Using the other test probe from the meter and touching it on terminals or fuses will give indication of power, potenial or voltage ( all mean the same thing) with refernce to negitive or ground of the 12 volt system. When using the probes free hand across any item like a light bulb if there is a negative and a postive the volt meter will show about 12 volts, good lamp or bad lamp. In the case of the fuse all of the items that are run by the fuse being tested in the same mannor, across the terminals of the fuse like a light bulb. The volt meter will show no difference of potenial or voltage if the fuse is good as the reference is the same at each probe. However if the fuse is blown or open circuit, the ground path flows through all of the lights and even the fan blower motor to present a negitive at one side of the fuse. The other side is positive but the circuit is open because of the blown fuse and shows about 12 volts.

In industry some fuses have a built in neon light blub across the terminals. When the fuse blows the light come one giving indication of an open or blown fuse.

Hope this explaination helps.

TonyK.

Grimsby Ontario Canada.
 
I had to read it out loud to myself a couple of times, but I think I get it. If the fuse was not blown, both sides of the fuse would be positive, so the probes would not detect a difference in potential and the reading would be 0. But since there is a break in the fuse, one probe is on the positive side, and the other probe is on the negative side because the rest of the circuit is providing the ground, so the meter shows a potential of 12V. So basically I was seeing voltage because there was no voltage going through the fuse, but because it was going through the voltmeter.
Therefore, when I'm checking circuits, if I see a voltage between two points, there is a break in the circuit somewhere between the probes.
But the switches confuse me. How is the circuit being completed if the switch to the item is off? eg. the blower motor.:dead:
 
Yes and No...

Try it like this...

Take the BLACK probe on most voltmeters which is COMMON or NEGATIVE... and clip it or hold it to the CHASSIS of the car or the NEGATIVE pole of the battery.

(Sharpen the probes with a grinder or file them so you can stab through PAINT or GREASE or DIRT and get a good ground connection on METAL. I also have STABBED wiring with the Positive probe also, right through the insulation. Works great!)

Take the RED probe and touch it to one side of the fuse. It should read 12 volts. Now touch the RED probe to the other side of the fuse... if it is a GOOD fuse, it too will read 12 volts. If BAD, it reads ZERO.

(In this case earlier... I believe you had both the Red and Black probes on each side of the fuse. When you did that, fuse A which was blown, showed the meter a difference in potential of 12 volts per side... and you were actually seeing the BATTERY... just as if you had put each probe on the one pole of the battery!

Now, all the good ones that showed NO difference in potential all read Zero... it was as if you had BOTH probes on ONE pole of the battery. Now I'm getting as confusing as Tony K., I bet!)

I can probably walk you though this thing over the phone sometime and you can see it better and it will POP UP clear in your mind for future testing. Its important to always GROUND the black probe to the chassis and look for voltage with the RED probe on the fuses or wiring or a terminals.

HEY... ya did good anyway!

This will NOT be the end of it though... especially after seeing sparks like you did... and... something CAUSED that fuse to blow! it'll most likely happen again!

Now... continuity testing is a different matter. I'll discuss this later if ya like...
 
What you wrote last made sense after several readings. I was getting a continuity test confused with a voltage test. My other multimeter has a continuity tester which makes a little beep when the circuit is complete, and that is what I've always used to test fuses. Naturally, I misplaced that little gem, and bought a new MM that doesn't have a continuity tester, so I didn't understand what I was testing and then misinterpreted the results. My dad always told me I tended to draw conclusions based on insufficient data generated by questionable results of faulty experimentation on irrelevant hypotheses.:D Thanks everyone for the help!
 
HA... that's what all Dad's say about everything...

... their kids try to do...

Glad you got the idea... and that MOP will work for now.

I'm not thoroughly convinced you understand all the theory you really need to know... but this will keep ya going for a while.

Your MM should have an OHMS scale for reading resistances... Where as you touch both probes together and the meter needle or readout should read "0" or ZERO. With the probes apart... INFINITY or no needle swing. Everything inbetween has some RESISTENCE to current flow, from NO resistance to current flowing (maximum) in the circuit for a ZERO reading, to an INFINATE amount of resistance (many, many Ohms) so that less or NO current flows.

A GOOD fuse reads ZERO (or shorted, in this case a good thing) so that current flows easily through it... and a BAD fuse would read INFINITY (or open).

(ALWAYS use the resistance scale with the power OFF or the companant (fuse or anything else) with at least ONE leg (fuse cap or wire) lifted OUT of the circuit. Otherwise you may be reading a resistance THROUGH another componant (giving you an inaccurate reading) or if there is power, blow up the MM or a fuse IN the MM.

Lesson #2 is now over... HTH...
 
You missed

"(Sharpen the probes with a grinder or file them so you can stab through PAINT or GREASE or DIRT and get a good ground connection on METAL. I also have STABBED wiring with the Positive probe also, right through the insulation. Works great!)"

Occasionally when trying to stab a wire through the insulation, the prope slips and goes half way through your finger.

Old hands know and new hands learn that one quickley.



TonyK.

Grimsby Ontario Canada.
 
I replaced all of the fuses with new ones. The turn signals work, but the clock, dome light, cigar lighter,and seat belt dinger don't. I know those are all on the same circuit and the fuse is good, so it's on to circuit tracing, I guess.
 
Yep... now this is where you need...

... to use caution as Tony K suggested.

Trace the wiring that should be powered and if you find it inconvenient to place a probe on a terminal or connector... you can CAREFULLY stab through the wire's insulation and "probe" a bit to see if power is present.
 
I'll sharpen my probes tonight. I think the parking brake warning light is on the same circuit. It stopped working before anything else. Then it seems like it was the dinger, then the clock, and most recently the dome light. Somewhere in the cigar lighter failed, too. I only ever used it for charging my cell phone and GPS. I can't imagine why they would go out one at a time like that.
 
Lets get focused.

The Cig lighter is off of an inline fuse with the wire harness cluster and has a brown wire on it. I can take a picture for you of what it looks like and where it is.

The Parking light indicator gets power from fuse A

Is there dash lights?

TonyK.

Grimsby Ontario Canada.
 
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Yes, I have dash lights. I changed all of the fuses I could find, including 2 inline ones. One 16 amp and one 8 amp. Both were down by the fusebox. The 16A one was in a white plastic holder and the 8A was in a green plastic holder. The only fuses that didn't get changed were the 3A ones.
 
Even with the new fuses,

check either side (or the output side) of the fuse to make sure 12vdc is making it all the way through. The fuse holder tabs can corrode and cause a bad connection.
 
The moment of truth.

The seat belt buzzer, the cicarette lighter and the dome light are all fed from the same inline fuse. Take your meter find a chassis ground for 1 probe take the other probe to the inline fuse and pull the stab connector out of 1 end of the inline fuse, you should now have voltage at one end or the other, ( key off ) if you do not then there is an open from the in line fuse wire to the the Bus connector. The seat belt buzzer/key buzzer goes through the key switch but is on the same inline fuse.

The bus connector should be under the fuse and relay tray. You will have to disconnect the battery and remove it from the cover it is mounted on. Possilby water has entered the tray and corroded a connection.

TonyK.

Grimsby Ontario Canada.
 
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