Stumped on parasitic draw on battery 2002 C70 convertible (faulty mirror switch) Topic is solved

Cees Klumper · Post by **Cees Klumper** » 01 Oct 2017, 10:20

Several times over the past mont, the battery was drawn down to completely empty without any obvious cause, like leaving an interior light on or the trunk lid slightly open as has happened before. The same thing has happened to me with two different batteries that I believe to be in good shape, so I don't think it's that. Also I checked the charging voltage which is well above 14 volt, so the alternator seems to be doing its job just fine (plus it was replaced by a Volvo garage a few years ago and there is no warning light on the dash). I have also looked for codes with an iCarsoft OBD reader and there's none.

As an electric systems novice, I did the searches here and, with a digital multimeter, set to measuring. I hooked it up in series to the positive battery terminal and cable and, long story short, have determined that there is a parasitic draw of 350 milliamps from just one fuse, no. 15. When I remove that fuse, the draw on the battery is only 40 milliamps for the whole rest of the car, which is well under the suggested maximum normal parasitic draw of 100 milliamps. So I think I have it narrowed down to Fuse 15.

According to the owner's manual, fuse 15 'runs' the interior lights, seatbelt reminder lights, door lights, trunk light, and the glove compartment light, and is rated at 10 AMPs.

Now for the part that has me stumped - when I switch off (interior and trunk lights) or otherwise test each of the various systems listed, the draw does not go away. It goes up when I turn the various lights on, open the doors etc, but it never goes below 350 milliamps no matter what. All switches seem to work, no lights stay on when switched off / doors closed etc, including in the glove box.

What could I be overlooking / is there some further test I can do to find the culprit(s)? Could there be other systems, such as the alarm (supposed to be under fuses 4 and 8, but I have never replaced that backup battery and I noticed the owner's manual is different from the card inside the fuse box, in terms of what systems are run through which actual fuses, so I guess it's possible both are wrong somehow), that I should be checking? Any tips much appreciated.

Post by **jonesg** » 01 Oct 2017, 10:47

I would try removing bulbs instead of turning lights off, to make sure it breaks the circuit.

If you find one that responds differently it might be a short or bad bulb socket?

Post by **jimmy57** » 01 Oct 2017, 11:50

Which fuse 15? Engine compartment, end of dash, or in trunk.

15 on the end of the dash is shown for the amplifier under right front seat. You could unplug the connector there and see if the draw goes away.

Cees Klumper · Post by **Cees Klumper** » 01 Oct 2017, 11:55

Thanks for the tips. This fuse 15 is under the hood. I'll try taking out the bulbs one by one, see if that helps. Hope I can sort this one out.

Cees Klumper · Post by **Cees Klumper** » 01 Oct 2017, 11:58

Sorry, should have specified this is our 2002 C70.

Post by **abscate** » 01 Oct 2017, 12:57

You've done 99% of the work finding the fuse with the draw, and 350 MA is way too much...that's 8 amp hour or 10% of battery per day.

I'll try find the wiring diagram and pass thoughts

Post by **abscate** » 02 Oct 2017, 04:48

I couldn't dig up the 2002 wiring diagram but I think the C70 mirrors the " bastard" 1999-200x early siting

That shows fuse 15 also feeds control voltage to the power window circuit, which I think is a likely suspect. Maybe locate the power relay there and try pulling that and testing load

Are you having any power window trouble??

Cees Klumper · Post by **Cees Klumper** » 02 Oct 2017, 05:29

Many thanks abscate - will pull that relay and check the draw. The card inside the fuse box also lists the power windows, however when I take out fuse 15, the power windows work jut fine without it, that's why I thought the card was wrong, also because the owner's manual does not list the power windows.
The windows have been working fine, although I have noticed that the driver's side window has started to make a more pronounced 'thunk' when it reaches the 'down' position. Maybe whatever switch tells the system that the window is at the bottom is not functioning as well anymore, or something else that causes the louder sound. Will check as soon as I have some time.
Plenty to help me keep diagnosing, I am sure I will get to the bottom of this with all of your help.

Post by **abscate** » 02 Oct 2017, 07:43

The card inside the fuse box also lists the power windows, however when I take out fuse 15, the power windows work jut fine without it,

Oh, thats always fun, trying to decipher wiring when the information is suspected to be bad...

Cees Klumper · Post by **Cees Klumper** » 04 Oct 2017, 10:40

Well, I feel really silly now. Turns out one of the make-up mirror lights, behind the sun visor on the passenger side, was permanently on. The switch that is supposed to turn it off when the sun visor is in the closed position, does not work anymore. My better half had used the light (that turns on when one opens a little 'door' to reveal the make-up mirror) and had not turned it off by closing the 'door', instead closing the sun visor expecting the light would turn itself off that way, as it should. The same switch on the driver's side stopped working a few years ago, and that light never works. So I could have known the other switch might also have gone bad. Because the sun visor was closed, I could not see the light (which is small, in fact it draws only 350 milliamps draw as I now know). Anyways, problem solved and it turned out to be very simple. At least I got to use my multimeter and learn the AMP function on it ... thanks for all the tips!