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![]() | Home > Technical > Parasitic battery drain - unable to measure current draw |
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jimbowats Member Since: 11 Apr 2018 Location: uk Posts: 45 ![]() |
To measure parasitic draw you need to connect a multimeter in series between the negative battery terminal and the neg lead..i.e disconnect the negative lead, set the multimeter to measure amps, connect in line with the neg terminal and neg lead(10a setting best) then lock the car.
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rambling rollie Member Since: 22 Jul 2017 Location: Port Elizabeth Posts: 62 ![]() ![]() |
How does one lock the car while the negative is disconnected?
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SYFL2 Member Since: 16 Jun 2012 Location: Sheffield Posts: 2608 ![]() ![]() |
I think when he said connect it inline to the negative terminal and negative lead it should lock ?
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rambling rollie Member Since: 22 Jul 2017 Location: Port Elizabeth Posts: 62 ![]() ![]() |
It varies, sometimes single sometimes double..
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DEG5Y Member Since: 22 Jul 2016 Location: Widnes Posts: 179 ![]() ![]() ![]() |
A current tester like this can help.
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jules Member Since: 13 Dec 2007 Location: The Wilds of Warwickshire Posts: 5148 ![]() ![]() ![]() |
Id disconnect the NEG battery lead and use a jump lead to bridge across to the battery. Lock the car. Connect up the multimeter between NEG lead and battery then disconnect the jump lead. Jules |
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davyboy Member Since: 30 Aug 2020 Location: Staffordshire Posts: 156 ![]() ![]() ![]() |
Good evening ptbalfour, I had this very unfortunate experience with my car where over a short period of downtime the battery was so dis charged sometimes it took quite a while to fully charge, having done the multimeter tests so many time I then realised the battery drain was sporadic, so looking at the wiring diagram in the Heynes manual traced where possibly the culprit was.
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Nodge68 Member Since: 15 Jul 2020 Location: Newquay Posts: 2086 ![]() ![]() ![]() |
The PTC heater shouldn't come on at all without the engine running, as it will discharge the battery in a few minutes. If was was coming on, it suggests some electrical gremlin is triggering the relay. It also shouldn't come on without the heater fan being on, or it can overheat causing fires, as it did in the Vauxhall Zefira.
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davyboy Member Since: 30 Aug 2020 Location: Staffordshire Posts: 156 ![]() ![]() ![]() |
Hi Nodge, yes your quite correct it heats the air but also assists with the coolant which aids quicker warm up in cold weather, the fault with mine was either the cabling or the thermostat, fitting the isolator disconnected the heater where the fault never returned plus never had a discharged battery.
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jules Member Since: 13 Dec 2007 Location: The Wilds of Warwickshire Posts: 5148 ![]() ![]() ![]() |
Interesting about the PTC abnormal heating. Its controlled by the ATC unit and takes input from ambient air temperature, Engine Coolant Temperature (ECT) and Heating request.
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Lightwater Member Since: 21 Aug 2014 Location: Sydney Northern Beaches Posts: 4914 ![]() ![]() ![]() |
If you have a clamp meter & the cable is long enough, or add a temporary section.
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