Battery Drained and Blown Fuse ...

[Duffman]

Sorry, this fuse does not cover the gauge lights, misread my diagrams! As Arne says above, it covers the dome light, glove box light, overhead light, step lights, map light, clock and windshield washer (if I read my diagrams better this time!). Will tackle each of these tomorrow!!!

[EScanlon]

That you are reading 12.5V between any two points in a circuit explains that there is a circuit running at 12.5v... but it doesn't tell you what amperage is running through there. That's the part that will blow a fuse, hence the ratings on a fuse are based on AMPS and not Volts.

You could have 12.5V and an amp reading in the hundredths of an amp... yet still have that 12.5V voltage potential with a high enough resistance in the circuit. Or the opposite, 12.5V with an extremely low resistance (as in a dead short) with an amp reading in the hundreds of amps (amp reading = current). Your short is causing enough of a high amp draw that it is blowing the fuse and presumably draining the battery.

Voltage, Resistance and Current are the three basic components in electric circuits.

E = I * R

E = Voltage or Potential I = Current or Amperage and R = Resistance

Your voltage is considered fixed at 12 (or in this case 12.5V). Your amperage, since you're blowing a 10A fuse is apparently higher than 10A, which points you to a resistance of 1 Ω or thereabouts.

But NONE of this is helpful in determining what is causing your problem.

So, go back to the light bulb in the cable clamp... does it cause the bulb to glow? If so, how brightly does it glow? That will tell you more of how much current (amp) you're running, plus give you a visual indication of the problem still existing until you can locate it ( by disconnecting the offending item).

When you installed the stereo, did you have the Heater Control Panel off the car? If so, did you then have the Map Light disconnected? What about the clock and glove box light? It is possible that you may have connected one of those wires to the wrong item? It isn't hard, especially the clock and glove box. Remember the clock receives BOTH a power and a ground wire.

The windshield washer wouldn't receive power unless the switch at the combination switch is continually depressed.

Step lamps weren't installed on the early vehicles although the circuitry is there. The Step Lamps or Courtesy Lamps were due to be installed on the door panels, that's why you have the funny little rounded rectangle "cut-out" that isn't cut out on the panels.

Did you recently unwrap the wiring for the step lights? It's at the extreme ends of the dash wiring harness, closest to where the wiring comes off for the actual room lamp door switches. They're usually wrapped in blue tape and have protective flexible sleeves on them. They're also both bullet receptacles so that you can't connect them to each other (which would short the circuit out).

Other than this, check to see if you accidentally pinched a wire when re-installing components. Again, not hard to do.

But that should give you something to start checking.

FWIW

Enrique

[Duffman]

Thanks, Enrique, your time is much appreciated!

[Duffman]

E, I went back through and disconnected the clock, lighter, dome light, etc. I also confirmed that the door and step light connections were disconnected. I ran my multimeter off of the negative terminal and the post and generated a 5 mA draw (sound right?). Therefore, not too much draw, I guess. Now, back to the blown fuse issue. After disconnecting everything, including the AC and stereo, I still cannot see anything wrong. I still cannot place a fuse in the holder without blowing, even with the ignition off. I am assuming a short at this point, though I have no clue where it could be. Would a short cause enough of a draw to blow the fuse, even if the ignition is off? Still looking for answers!!

[Arne]

Stephen, the 5 mA draw is probably correct, as the short will not be evident when the fuse is blown or removed. Since the circuits that fuse protects are all hot all the time, the ignition being on or off is immaterial.

Here's the fact. You do have a short, and it is somewhere in the wiring that the blown fuse protects. Since you can't keep a fuse in it without blowing, continuing to look for a draw is pointless. If disconnecting the easily identified items it powers has no effect, you're going to have to look deeper.

Time to switch to the ohmmeter. With the fuse removed, measure the continuity between a good ground and the protected side of the fuse (the part that goes to the devices, not the part that has 12v at all times). Since the fuse blows instantly, you should see very little resistance. From there, follow the wire(s) out of the fusebox and toward the devices, checking resistance as you go. This will take time and some contortions to get under the dash and trace the wiring.

My guess at this point is that you either have some wire connected wrong somewhere, or a wire has rubbed through the insulation and is shorting directly to ground.

[geezer]

I think your car is too early to be an automatic transmission, so try disconnecting your windshield washer motor, then replace the fuse. If that's not the source of the short, you will have to isolate the entire circuit one leg at a time and perform several continuity checks to ground to find the culprit. That may mean the need to cut the wire at splice locations just to isolate a particular leg of the circuit. Sometimes that's what it takes to track down a well hidden short.

[Duffman]

Thanks, Arne and Ron, it is frustrating, but there has to be a simple solution, as most electrical issues have one. Time to track the short!!!

[EScanlon]

A 5mA = .005A, which is indeed a very small current. This amount is normal when the clock is operational.

However, I wonder why you would have such a small current, yet still be blowing fuses. Is there another wire that connects to the battery, other than the main battery cables?

I still cannot see anything wrong. I still cannot place a fuse in the holder without blowing, even with the ignition off. I am assuming a short at this point, though I have no clue where it could be. Would a short cause enough of a draw to blow the fuse, even if the ignition is off?

You might NOT notice anything wrong. The fault could be under a dash support that pinched a wire, a screw that clamped into something far enough that it pierced the insulation....the list could go on and on.

A short is the most typical reason for a fuse blowing. This is a simplistic explanation, but the MAIN purpose of a fuse is to NOT allow large current flows through a circuit. Kind of like a check valve, if the flow (current) gets too high, the fuse blows and shuts down the circuit.

The ignition being on or off only helps identify which portion of the car's circuitry your short is in. If it were ONLY when the ignition were ON, then you could limit your search accordingly, but with it being on OR off, it tells us that the short is in a wire that is "live", i.e. has 12v+ at ALL times.

Have you checked the glove box light? That switch/bulb holder wouldn't need much of a connection to short out.

But, out of all this discussion the "signs" point back to the stereo install. That's the "new" item in the mix and your problems date SINCE that point, unless you had never noticed them before. Granted the dome light isn't very bright but surely you would have noticed.

You mention disconnecting the stereo, but I'll bet that like most of us, you would have disconnected the connector at the back of the radio and not the individual wires that you fed and connected to the car's circuitry. That may be where your problem lies. It may be the ground for the speakers, the ground for the radio, the antenna connection, the faceplate light, or any one of several other connections. ONE of those may be causing the problem.

If you did the install, then it's easy to go back and re-check your work. If on the other hand you had someone else do it, they may have picked the first wire that they could detect 12v from. This has happened many times before and gets repeated time and time again.... check the "new" installation.

Sometimes you have to go back to the very VERY beginning, so with that in mind:

We are talking about the fuse on the right side of the fuse box, fourth one down from the top, aren't we? I'm sure you have it labeled, or are reading from the lid, but this is also something to check.

Have you checked underneath the fuse box to ensure that no wires are touching the fuse terminals from below?

Don't think I'm trying to patronize you, I'm not. Sometimes even the "experts" get a little baffled and that's when you have to step back, take a deep breath and relax.... then you start from the beginning. Oftentimes it's the "boneheaded obvious" item that jumps out at you and you realize.... ooops!

Walk it through a step at a time.

E

[Duffman]

Good points, E, and will doublecheck them all.

I have checked on resistance, per Arne, and have found no resistance (0 reading) for all connections to clock, dome light, washer, glovebox and door lights. Does that mean anything? Would have thought that I would have run into some kind of reading by now, reflecting a short..

[Duffman]

Confirmed my stereo was totally disconnected from the power source, also made sure the ground was good on the stereo, which it was. Don't think it is the stereo itself causing the problem.

[Arne]

I have checked on resistance, per Arne, and have found no resistance (0 reading) for all connections to clock, dome light, washer, glovebox and door lights. Does that mean anything?

No. You need to start your resistance tests at the other end. You have a wiring problem, not a device problem. Start at the fusebox and work towards the devices.

I'd unbolt the fusebox from the body and turn it over so that you can visually begin tracing the entire circuit. Don't trust wiring diagrams.

Just a thought - when you have the fusebox turned over, trace the wire to the cigar lighter. That is also hot all the time, regardless of ignition.

[Duffman]

Thanks, Arne, will do. Checked the lighter, it is not connected at this time.