Huge Amperage Draw 84 944

rporzio · 06-25-2013, 07:44 AM

I've tried everything I know of. All fuses one at a time, relays the same and still get what I'm reading as a 2 amp draw with everything off. My multimeter goes to an overflow reading on ma setting because I think it's capacity is 400ma. So now I'm used the unprotected 10 AMP max to get any sort of reading I can work with or see go down to know I've found something.

In addition I've taken the faceplate off the head unit and disconnected power to the amp.

I have narrowed it down to one of the 3 red wires (one to the fuel pump (BlueRed)and the other 2 to the fuse panel) that leave the battery and head towards the fuse panels but how can you tell where they go from there?

Just looking for some fresh experienced ideas as I'm running out of them!

Thanks, Ralph

rporzio · 06-25-2013, 08:09 AM

I said I took all the relays out but that's not the case; I only took out the horn and rear defogger relays. Do you think it's necessary to remove them as it's incredibly hard for me to get in a position to remove them easily. I'm hoping that removing all the fuses did the same thing but you guys know way better than I if that's true. R.

mikepellegrini · mikepellegrini's Garage

Mmm. If you've pulled every one of the fuses and the draw is still there, how about disconnecting the accessory wires leading to the positive terminal one by one? Maybe that way you could isolate which circuit?

rporzio · 06-25-2013, 09:41 AM

help me with that, what are the accessory wires, do you mean on the fuse panels or the battery? I hope you mean the battery because I can't imagine how I can get up behind the fuse panel to remove wires, yow! R.

mikepellegrini · mikepellegrini's Garage

Naw. I mean the smaller, extra wires leading off the positive terminal on the battery. My cars both have 3-4 extra wires. I forget what they go to. Just a long shot...

rporzio · 06-25-2013, 10:56 AM

ok that's better. I did that and have narrowed it down to 1 of the red ones. I can't tell by looking at the wiring diagrams where they actually go. R.

mikepellegrini · mikepellegrini's Garage

Well that's cool.

I don't remember where those all go but maybe someone else will.

mytrplseven · mytrplseven's Garage

Now that you're down to one, Try everything in the car and see what doesn't work and you should have a clearer idea of which leg is affected. Even though you may initially find something, keep going and check everything including lights, turn signals, defrosters, etc. Once you've narrowed it down, use the wiring diagrams to see what else is on the circuit. My wife's car was draining the battery and when I disconnected the alarm module, things got right.

rporzio · 06-25-2013, 02:09 PM

Thanks Mike and Mytr, I really need to do a little more testing because I just discovered that the potential is on both reds going to the fuse/relay block. I really need to make sure I'm reading my findings correctly before taking up any more of this forum's time and talent. How did you disconnect the alarm module, the switch/plunger under the hood? R.

NBTF · NBTF's Garage

In looking at my Haynes book it is showing, from the battery + side, a Red/Blue (Fuel pump relay), a black wire (Starter), and 2 red wires supplying power to (line A) [Light switch, fuse 5, fuse 6, fuse 7, fuse 9, horn relay, ignition/starter switch, and additional fuse board fuse 3 &4].

Also has there been any aftermarket electronics, lights, or anything else added to the car?

Hope it helps.

rporzio · 06-25-2013, 02:37 PM

That's interesting NB, with just the red blue connected I have no draw, its the 2 red wires. Yes there are some additions. I pulled out the head unit completely and disconnected power to the sub and all the interior lights (not the dash/instrument lamps) are converted to LEDs but they are in the off position.

Are you reading in the Haynes that one of the red wires goes to the main fuse panel and the other goes to the additional? Thanks for helping! Ralph

AKCJ · 06-25-2013, 02:43 PM

Ralph,

You may have already figured this out but, if you're measuring the extra small wires at the pos battery side make sure you disconnect all the wires to the pos batt when you take the measurement. You could even try taking a measurement with all wires disconnected and then more measurements as you contact the other wires to the pos post one at a time.

I recently did some wiring troubleshooting and a friend showed me how it can make a difference.

I don't expect that this is really part of the problem but it would be good to eliminate it. My car has the main heavy wire to the starter plus 3 auxiliary wires ( I don't know where they go). Plus I've got other add on wires for stuff like the stereo & trickle charger. I recently installed a military style clamp and I recommend it.

Regarding removing the relays from the fuse box. On my 83 the fuse box (or at least one of the two) can be pulled down for better access. It's very hard to R & R relays with the panel in place but much easier after you get it pulled down.

Good Luck

NBTF · NBTF's Garage

Made a scan of page 1 of the electrical for the 84.

rporzio · 06-25-2013, 03:07 PM

Thanks Ak, those are great ideas and good cautions. That's exactly how I discovered that my friends the red wires are the culprits. NB, that diagram is very similar to the Porsche manuals in that you can see the 2 red wires going to the same spot which I assume is a bus type of feed to the various fuses. I'll get back on this on Thursday and report back to the board with any additional findings I may have. Thanks everyone! Ralph

djnolan · djnolan's Garage

It could be caused by a short in the alternator. I think it is related to a bad rectifier. Had a similar problem and had to get the alternator rebuilt to fix it. This was an 87 late car.

rporzio · 06-26-2013, 03:21 AM

I've heard that dj, how in the world do you prove it to that piece? I can't even see mine and is there a connector on it to take off? R. Thursday more research int this issue, not today.

rporzio · 06-26-2013, 05:38 AM

another interesting thing I noticed yesterday is the meter displays a 2.16 amp draw then lowers nearly every time I measure. This happens even with the cable to the starter removed and only the red wires attached, do we have some capacitors in the circuit that get charged every time connections are made? R.

djnolan · djnolan's Garage

An initial draw of several amps may be the stereo. What does it read after it stabilizes?

To check the alt use an ohm meter across the main alternator terminal to ground. Or disconnect the alternator wire while checking the resistance at the batt terminal to see if the draw goes away.

rporzio · 06-26-2013, 05:47 AM

No dj, I have the head unit completely out of the chassis and the sub disconnected. I'll look into your help to check the alt on Thursday. Your last sentence, where is that alternator wire, on the alt itself. Let me make sure I'm getting the readings correct before I commit to what I'm reading after what I think is a cap charging. More tomorrow, I can only comment here and there today but can't do any work on it. R.

djnolan · djnolan's Garage

There are many other possible causes than the alt.

Worn insulation on wires, especially in the power windows.
The door light switch on drivers side shuts off the computer when the door closes. If this is bad then you will get a run down batt.
Stuck relays if you haven't checked them all.

Sometimes it is easier to check the resistance to ground than to check the amp draw. you can calculate the amp draw by the formula 12v divided by the resistance (12/R) = I (amps)