Short circuit - battery isolator?

[mikinoz]

Hi there,

I have a problem where I only drive the MK1 once a week and between drives, it manages to flatten the battery.

I did install a radio and that was on the main constant voltage, so maybe that is the issue and it should be on a switched accessory voltage. I always remove the face plate when I leave the car. I should remove the head unit as a test I spose.

Besides that I am wondering if installing a battery isolator/kill switch would be of benefit, and if so, how one goes about installing it. I am pretty sure they are a straight forward switch that cuts the + cable and breaking the circuit, but is there any other consideration I need. I will most likely just run the switch internally, and not penetrate a panel to expose it from the outside.

And yes, I could just disconnect the battery, but that will require a shifter every time.

Thoughts? Cheers. Mick.

[Peter Jones]

You can get an isolator that goes on the battery itself which is the easiest install. I've got one on my white golf.



It just goes between your battery post and the cable.

Mounting something internally that shuts off the battery completly will need a big switch and a lot of expensive heavy duty cabling.

What might be a better option in your case is just to wire in a switch to isolate to main feed into the fuse box. (If that's the source of the current drain)

I'd probably try and figure out what is draining the battery first though. You'll need an ammeter to do this. A multimeter with a 10Amp current range will do the trick.

With the multimeter on it's 10 Amp setting and the leads connected to the right test sockets-

• Ignition off - disconnect battery and measure current between the battery post and the battery lead - that's your total leakage.
• Ignition off - battery connected - remove each fuse in turn and measure the current across each fuse - this will tell you which circuit is drawing the power.

If the sum of the current accross the fuses is less than the current at the battery then it's going somewhere else. In an unmodified MK1 there aren't many things connected to the positive terminal of the battery. There should be a big lead to the starter, one to the fusebox and one to the alternator.

Sometimes alternators can develop internal faults that can drain the battery so remove the alternator lead from the battery and measure between it and the battery to see if the alternator is drawing power.

If there's anything else connected directly to the battery you can use the same method to see if there's current flowing when it should be off.

Just a word of warning though don't try these tests with the ignition on unless you're very sure the circuit draws less than the rating of your ammeter or you'll blow it's internal fuse.

There's the possibility that your battery is faulty too. Leave it disconnected for a few days and see if the issue goes away.

Happy hunting.

Pete

[mikinoz]

Thanks Pete. I thought I would that I should update you and advise that tonight the car started after charging the battery on Sunday. I did disconnect the radio so if I can still start it on the weekend, then I reckon that may be draining it. I will connect the radio power to the accessories and maybe that will sort it out... Where can I locate an isolator like yours?

[Peter Jones]

i found that one in an auto shop many moons ago. Also try boat shops or 4wd places.

Pete

[blutopless2]

There is the potential for a dud battery here. If its dropped a few cells then it wont hold charge and may get really hot, also be careful of any fluid coming out of it.
I would test each circuit to see which one is using power.
Unlikely that the memory for the radio is draining it, unless the radio is only on standby mode rather than completely off.

[mikinoz]

After a whole week with the radio disconnected sees the car continue to start. I have no idea where I have gone wrong with wiring it in, but need to make a reassessment.

Thanks all for the input.

[mikinoz]

I knew it was too good to be true. Battery flat tonight. Isolator coming to a battery terminal near you soon.

[mikinoz]

Bought an isolator but think that the issue is with one of the relays on the driving light circuit, so I have disconnected that and see how long the charge lasts...

This is worse than looking for weep leaks in walls..