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Continuity Test
The Baron - 15/7/17 at 11:36 AM

After being away from the kitcar scene for 6 years, I'm back!

I have pulled my locost out of the garage and cleaned off lots of cobwebs, dust and heaven knows what else! Including a mouse or two has eaten my seat pads

No shocks, but the battery was dead (won't hold charge either)

But a jump from my daily car and started straight away!

Question:-

With the battery leads disconnected, ignition off, I get continuity..... Should I?

Thanks in advance

Baron


adithorp - 15/7/17 at 01:17 PM

Possibly depending on how it's wired. An immobiliser might have a permanent live as could the ECU or clocks.


tegwin - 15/7/17 at 01:31 PM

Yes its not a surprise.

Loads of systems on board that might have a path from +ve to gnd via a capacitor or resistor etc which would give you continuity of sorts..

Better tests may be to measure the resistance across the cables or perhaps to measure the amperes drawn with the battery connected and nothing turned on.... Id expect a few mAh draw.


gremlin1234 - 15/7/17 at 03:01 PM

how are you checking continuity?

can you try checking again with the probes reversed?

reason for asking is you could be detecting the diodes in the alternator
this page shows a fairly standard layout of alternator wiring and it's diodes.
https://www.picoauto.com/library/training/the-alternator


britishtrident - 15/7/17 at 03:07 PM

It is called parasitic drain and almost every car on the road has it. Most modern tintops have 50 to 70 ma parasitic drain after everything has shut down and gone into sleep mode.
You can measurethe Key Of Engine Off drain current directly with a DMM on amps mode, if more than about 80ma I would investigate it. With current drains if the draincurrent is high the alternator diodes are a prime suspect --- simply check the drain current with alternator disconnected.
To track it down if you have a good quality DMM you could try looking for tiny voltage drops each blade fuse.
See this YouTube from Matt at Schrodinger's Box channel



[Edited on 15/7/17 by britishtrident]