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odd parasitic drain problem (main fuse 7?)

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1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
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marwood82
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Year and Model: 1997 V70
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odd parasitic drain problem (main fuse 7?)

Post by marwood82 »

Hi,

im having issues chasing parasitic drain on my 1997 v70 i'm hoping someone can help.

if i leave the car parked, the battery voltage is dropping 0.18- 0.2V per day so its flat inside a week.
i've tried 2 batteries(1 brand new), same problem.

what makes no sense is that the multi-meter reads a drain of 0.02A which surely should be fine?
i've tried the standard drain hunt by pulling fuses 1 at a time and not seen any significant change to the current

what is really odd though is that i can get the voltage drop to stop if i pull fuse 7 (50A) from the main fuse box.
but looking at the label it simply states ' power to fuse box'
does anyone know how fuse 7 is wired and what in the secondary box it actually goes to? (or any other suggestions?)

also i have the factory built in dash sat nav(with the flip up screen and the cd drive in the glove box) but theres no mention of it on any of the fuses, does anyone know how its wired into the car?(i'm trying to rule that out as a possible cause)
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abscate
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Re: odd parasitic drain problem (main fuse 7?)

Post by abscate »

Are you measuring current drain from the disconnected negative battery terminal to the battery post and only recording 20 mA?
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zhenya
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Re: odd parasitic drain problem (main fuse 7?)

Post by zhenya »

If you are only seeing 20mA parasitic drain and that is verified as correct and not varying, do the calculation and you can figure out how long the battery should last. My recollection is that 20mA is well within spec.

I have an old thread around here where I chased down a parasitic drain on my 855 that even my Volvo indy couldn't fix. It turned out to be bad diodes in the alternator. But I recall that my drain was in the 60-80mA range.
marwood82
Posts: 10
Joined: Tue Nov 15, 2016 2:22 pm
Year and Model: 1997 V70
Location: germany

Re: odd parasitic drain problem (main fuse 7?)

Post by marwood82 »

abscate wrote:Are you measuring current drain from the disconnected negative battery terminal to the battery post and only recording 20 mA?
yes,thats how im measuring it.
zhenya wrote:If you are only seeing 20mA parasitic drain and that is verified as correct and not varying, do the calculation and you can figure out how long the battery should last. My recollection is that 20mA is well within spec.

I have an old thread around here where I chased down a parasitic drain on my 855 that even my Volvo indy couldn't fix. It turned out to be bad diodes in the alternator. But I recall that my drain was in the 60-80mA range.
my back of the envelope calculation based on typical voltage capacity curve put the current draw at at least 10 times what i'm seeing on the meter.

i considered the alternator but if i pull the main fuse 7 then the drain seems to stop so it must be something on that circuit.

i noticed during my fuse pulling test, fuses 8 and 15 and both caused a brief spike in the current reading when i put them back in so they are clearly drawing some power but it i dont see a drop when they are out and post spike it immediately returns to 0.02A.

(8=Immobilizer ,headlight switch)
(15=Courtesy lights, door open warning lights, trunk/cargo space light, seat belt reminder, glove compartment light )

i left main fuse 7 in and left secondary fuses 8 15 out overnight and this morning the voltage had barely changed.

i can't find wiring details for the 97, but i found these http://www.matthewsvolvosite.com/downlo ... ersion.pdf
i guess its not set up too differently?, that points main fuse 7 at secondary fuses 11-17.

given fuse 15 seems to be on the same line as main 7 i might finally be on to something!

fuse 15 certainly would make sense, it wouldn't be the first time a stuck light has caused someone a problem, however i dont get why i dont see a current draw?
(i guess it could be possible i have a duff meter!)

is there a light or something on that line that will switch off when i disconnect the battery but then take so long before it comes on again when power returns that i would have stopped my current check before it kicked in? (i probably spent 15 mins pulling the secondary fuses last night so it would need to wait at least that long)
Last edited by marwood82 on Wed Nov 16, 2016 9:42 am, edited 1 time in total.
zhenya
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Re: odd parasitic drain problem (main fuse 7?)

Post by zhenya »

Here is my thread where I solved my issue, including descriptions on how I tested the alternator circuit in isolation of the rest of the vehicle's electronics to verify the bad diodes on page 3. Lots of helpful stuff that might be of use here. viewtopic.php?f=1&t=34437
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Re: odd parasitic drain problem (main fuse 7?)

Post by abscate »

Test your meter by opening the glovebox and seeing if the light draw registers. The glove box light has been reported here to stick on, and you test it by recording a video on a smart phone while closing the door
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marwood82
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Year and Model: 1997 V70
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Re: odd parasitic drain problem (main fuse 7?)

Post by marwood82 »

abscate wrote:Test your meter by opening the glovebox and seeing if the light draw registers. The glove box light has been reported here to stick on, and you test it by recording a video on a smart phone while closing the door
well, i put fuse 15 back this morning and this evening the voltage has dropped again. so i've removed it and if in the morning the voltage still the same then i think ive at least identified the circuit.

i did try the phone in the glovebox test early on in this and it did seem to be switching off.
the light thats supposed to come on when you open the boot doesnt work so maybe its that?

is there a list somewhere of all the lights that are on this circuit?
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Re: odd parasitic drain problem (main fuse 7?)

Post by scot850 »

You could have the famous trunk/tailgate harness broken wires that may be draining the circuit if the wrong wires are shorting. Check the wiring in the LH tailgate hinge area.

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Re: odd parasitic drain problem (main fuse 7?)

Post by beigg »

Pull the connector for the glove compartment light, and disconnect the hatch harness in the cabin. If the battery doesn't deplete, connect one of them back and repeat process. In a day's work this should be ample time to reveal the juice drawing ghost.
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Re: odd parasitic drain problem (main fuse 7?)

Post by misha »

Does trunk light turning off after tailgate is closed?
'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / polar white wagon
'91 Citroen XM 2.0 SI /fully equipped/mandarine red metallic
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
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