Parasitic draw multimeter question
#1
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I just got a 1990 S4, and after getting a bunch of the initial stuff fixed up I realized that I have a sizable parasitic draw issue. I haven’t been able to test exactly how long it takes to completely kill the battery, but it’s a couple of days tops. Anyhow, I have strong suspicions that it is the aftermarket stereo, but I want to get a baseline reading first to see how much “leakage” I am getting. I read in an old post that I should disconnect the ground strap and bridge the strap to the chassis using a multimeter set to 200mA. I did this, but I’m not getting any readings so I’m assuming that I’m doing it wrong. I am completely inept at all things electrical so I apologize for what is probably my first in a series of stupid questions, but is my multimeter on the correct setting? If not, how should it be set?
Last edited by Simon928; 07-11-2016 at 11:37 AM.
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#4
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There is quite likely a 5 amp mini fuse in the back of the meter that is in the circuit when you are on the mA scales. If you drew more than 5 amps for any small amount of time with the meter connected(like opening a door, or turning on the key), you blew the fuse.
Start on the 10A position, and see what you get. Then, remove the back of the meter and check for the fuse. It will be a small round one, or might be a mini blade fuse, either way it needs to be replaced, and then be very careful when you have the meter connected to those terminals, that you don’t over current load it.
Start on the 10A position, and see what you get. Then, remove the back of the meter and check for the fuse. It will be a small round one, or might be a mini blade fuse, either way it needs to be replaced, and then be very careful when you have the meter connected to those terminals, that you don’t over current load it.
#5
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Just for giggles I tried a different multimeter that I had lying around using the exact same settings and I got the exact same results–a 0 reading. I tried plugging the red cable into the 10A socket and I got a reading of 13.2. It is certainly possible that both multimeters have the same blown fuse, but I just thought I’d test the other one since I had it lying around. I’ll see if I can find a 5 amp cylindrical fuse at a local store to confirm.
#6
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Eric the Car Guy and many others offer tutorials/fixits on various subjects including this one.
Fully charge the battery.
Everything is off: key is out, door closed, etc.
Red lead goes into the Amp side.
Set meter to DCA 10 (20 if you have it).
Disconnect negative cable.
Connect red lead to detached negative cable.
Connect black lead to negative post.
Read it and weep. (The most you should have is 50mA.)
Disconnect meter. Open door. Tape door switch closed. Reconnect meter.
(Hyperlink to eBay NOT my doing.)
Pull the fuses one at a time with fingers crossed.
Fully charge the battery.
Everything is off: key is out, door closed, etc.
Red lead goes into the Amp side.
Set meter to DCA 10 (20 if you have it).
Disconnect negative cable.
Connect red lead to detached negative cable.
Connect black lead to negative post.
Read it and weep. (The most you should have is 50mA.)
Disconnect meter. Open door. Tape door switch closed. Reconnect meter.
(Hyperlink to eBay NOT my doing.)
Pull the fuses one at a time with fingers crossed.
Last edited by curtisr; 07-11-2016 at 08:30 AM.
#7
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Thread Starter
Thanks for that video! I just watched it and if I go with the 10A reading that he is talking about it looks like I have a draw of 1.34A. Just a couple more questions before I start pulling fuses:
1) Is it okay to have the hatch open while I am doing this test? There are no interior lights turned on while the hatch is open (they’re all swtched off).
2) Related to the first question, even if all of the interior lights are switched to the off position, I assume I should still keep the passenger side door switch closed while pulling fuses, is that correct?
1) Is it okay to have the hatch open while I am doing this test? There are no interior lights turned on while the hatch is open (they’re all swtched off).
2) Related to the first question, even if all of the interior lights are switched to the off position, I assume I should still keep the passenger side door switch closed while pulling fuses, is that correct?
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#8
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Thanks for that video! I just watched it and if I go with the 10A reading that he is talking about it looks like I have a draw of 1.34A. Just a couple more questions before I start pulling fuses:
1) Is it okay to have the hatch open while I am doing this test? There are no interior lights turned on while the hatch is open (they’re all swtched off).
1) Is it okay to have the hatch open while I am doing this test? There are no interior lights turned on while the hatch is open (they’re all swtched off).
2) Related to the first question, even if all of the interior lights are switched to the off position, I assume I should still keep the passenger side door switch closed while pulling fuses, is that correct?
#9
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Simon,
I bet if you took in the Sharks in Ontario gathering later the folks there could nail this in short-order. Pun intended. (See sticky if you aren’t familiar with this annual event.)
I bet if you took in the Sharks in Ontario gathering later the folks there could nail this in short-order. Pun intended. (See sticky if you aren’t familiar with this annual event.)
#10
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Thread Starter
Thanks for the answers! Yeah, I do plan on making it to Sharks in Ontario. I’ll still do my best to try and diagnose the draw before I get there, but if it is still acting up I’m sure the group would be able to figure it out really quickly. Since jumping in with both feet is how I learn, I don’t mind at least attempting to fix this on my own.
Speaking of which, there is one more thing that I’d like to figure out before I can start to accurately diagnose the problem. It seems like one of the PO’s changed fuse #19 from it’s original purpose (Headlight washers) to be the circuit for the radio. I can’t say for sure if the Headlight Washer wiring has been removed or not, but the fuse that is normally in that slot is a 25A and what’s in there now is a 5A.
As you can see in the pic below, there is a red wire that goes into the front of the CE Panel at fuse 19. Since this looks like an obvious “situation of interest” I took the fuse out to take a look at what was going on in there but the wire fell out when I pulled out the fuse. Even though I know that this wire shouldn’t be hooked up like this, I would like to put it back to how it was so that I can have a baseline which I can start diagnosing from, but the problem is that I am not sure how this wire was hooked up as I am not familiar with how the inside of a fuse block looks. Is there a prong that this wire would’ve wrapped around or something?
,
Speaking of which, there is one more thing that I’d like to figure out before I can start to accurately diagnose the problem. It seems like one of the PO’s changed fuse #19 from it’s original purpose (Headlight washers) to be the circuit for the radio. I can’t say for sure if the Headlight Washer wiring has been removed or not, but the fuse that is normally in that slot is a 25A and what’s in there now is a 5A.
As you can see in the pic below, there is a red wire that goes into the front of the CE Panel at fuse 19. Since this looks like an obvious “situation of interest” I took the fuse out to take a look at what was going on in there but the wire fell out when I pulled out the fuse. Even though I know that this wire shouldn’t be hooked up like this, I would like to put it back to how it was so that I can have a baseline which I can start diagnosing from, but the problem is that I am not sure how this wire was hooked up as I am not familiar with how the inside of a fuse block looks. Is there a prong that this wire would’ve wrapped around or something?
Last edited by Simon928; 07-11-2016 at 11:36 AM.
#11
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Sometimes people strip back the insulation, wrap the wire around the upper neck of the fuse blade, then stick it in the socket in a demented attempt to get a ‘fused’ circuit to their accessory. This appears to be the case here.
Do NOT put the red wire back on the fuse.
Put the correct amperage fuse in the location.
Set up your meter in the hatch, visible from the outside.
Have your helper stand outside the car with the hatch closed, and doors closed.
Scrunch yourself into the passenger foot well(or remove the pax seat).
As your helper records the readings, sequentially remove fuses from the block. Note the fuse where there is any change in the amp reading upon pulling a fuse(ex; fuse 19 removed, reading drops from 1.3 to .450)
After all fuses are out, start pulling relays sequentially, note any amp changes. (a hot dog tong is useful here)
Report findings.
Do NOT put the red wire back on the fuse.
Put the correct amperage fuse in the location.
Set up your meter in the hatch, visible from the outside.
Have your helper stand outside the car with the hatch closed, and doors closed.
Scrunch yourself into the passenger foot well(or remove the pax seat).
As your helper records the readings, sequentially remove fuses from the block. Note the fuse where there is any change in the amp reading upon pulling a fuse(ex; fuse 19 removed, reading drops from 1.3 to .450)
After all fuses are out, start pulling relays sequentially, note any amp changes. (a hot dog tong is useful here)
Report findings.
#12
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A new shark, congrats Simon.
Once you correct that PO wiring you should be on your way to a tidy electrical system. I spent months on my 85 pulling wires and putting it back to stock.
Once you correct that PO wiring you should be on your way to a tidy electrical system. I spent months on my 85 pulling wires and putting it back to stock.
#13
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It looks like you haven’t any unused fuse slots but you can confirm that easily enough by checking a CE diagram. If there is supposed to be one you can figure out if it is in use also easily enough.
Otherwise you can attach the red wire to a jumper fuse (say 10 amp) and find the power (on in the run or accessory) position in one of the unused relay sockets with a test light or multimeter. I would add a male connector to the jumper fuse but I guess that goes without saying.
Otherwise you can attach the red wire to a jumper fuse (say 10 amp) and find the power (on in the run or accessory) position in one of the unused relay sockets with a test light or multimeter. I would add a male connector to the jumper fuse but I guess that goes without saying.
#14
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Thread Starter
Thanks very much for the instructions Doc, I’ll see if I can get a helper this evening and report back with my findings.
Adam, thanks for the congrats! I think I’ll be pretty happy with this car once I start getting stuff like this sorted out. Hopefully you’ll be able to see it in person in a couple of weeks.
And Curtis, thanks for the further tips. I do have an unused slot in fuse socket #32, and the fuse/relay chart also says that this slot is unused. Are you saying that I can just hook the red wire up to this fuse to test its draw?
Adam, thanks for the congrats! I think I’ll be pretty happy with this car once I start getting stuff like this sorted out. Hopefully you’ll be able to see it in person in a couple of weeks.
And Curtis, thanks for the further tips. I do have an unused slot in fuse socket #32, and the fuse/relay chart also says that this slot is unused. Are you saying that I can just hook the red wire up to this fuse to test its draw?
#15
Nordschleife Master
Something to keep in mind – Even with all the interior lights off, the little red warning lights in the backs of the doors will be on if a door (or the hatch) is open. There might be other stuff that turns on with the doors open too. I’m not conversant on the wiring specifics of a 90.
That’s why Doc’s suggestions included both “put the meter where your helper can see it through the hatch” and “Scrunch yourself in the passenger seat.”
That’s why Doc’s suggestions included both “put the meter where your helper can see it through the hatch” and “Scrunch yourself in the passenger seat.”
