Flat Car Battery And Key Battery

[Learuss]

Hey all,

I have a 2001 VX which hasn’t been used for 6 months as I’ve been out the country. I’ve just come to start it and 2 problems 1. Car battery is flat, which is an easy fix, just jumpstart it… nope.
Problem 2. Key battery is also flat. I have a spare key from mister Minit that was never programmed to the car… I’d known original key was on its way out but stupidly never programmed it with the car and it was just sitting in a drawer.

Before I left for overseas I got the old key to work by heating it up with a hairdryer enough to remotely open the car and start the ignition. Now nothing.

I have no idea which issue to address first. Can I disconnect the immobiliser and jumpstart the car?

I used the original car key to open the car but when I put in the ignition nothing.

Any advice taken. Car is only worth $500 so don’t wanna spend a lot if I can help it but need transport asap.

 

[Lex]

Hey all,

I have a 2001 VX which hasn’t been used for 6 months as I’ve been out the country. I’ve just come to start it and 2 problems 1. Car battery is flat, which is an easy fix, just jumpstart it… nope.
Problem 2. Key battery is also flat. I have a spare key from mister Minit that was never programmed to the car… I’d known original key was on its way out but stupidly never programmed it with the car and it was just sitting in a drawer.

Before I left for overseas I got the old key to work by heating it up with a hairdryer enough to remotely open the car and start the ignition. Now nothing.

I have no idea which issue to address first. Can I disconnect the immobiliser and jumpstart the car?

I used the original car key to open the car but when I put in the ignition nothing.

Any advice taken. Car is only worth $500 so don’t wanna spend a lot if I can help it but need transport asap.

Do you have a battery charger, or can you borrow one? Try charging the battery over night..

Maybe the battery is no good & needs a new one?

Add some fresh fuel.

When its got a good battery, sit in the car & try locking & unlocking with the key fob.
If locks & unlocks ok, try & start it.

 

[RiffRaffMama]

My son swears up and down that if you touch the keyfob to your head when you press the button that it works better.
But like Lex says, a good battery may be what the car needs to communicate with the keyfob. It takes a long time for the keyfob batteries to die, and it'd be the most bizarre coincidence if both batteries died at the same time. If your car battery has been flat long enough, it won't recharge, no matter how long you hook it up to a charger for.

 

[Fu Manchu]

Yep. Battery first.

Avoid jumpstarting. Voltage spikes aren’t great for fragile module circuits and they are getting hard to find.

Charge the battery out if the car

Then if the battery holds charge, the car will start. The key will get 3V via the slip ring to power the key.

Then you can go through key linking processes.

 

[RiffRaffMama]

Then you can go through key linking processes.

Can you do that yourself? I always thought you needed a Tech II or something to be able to program a blank key to your car? You can get a thing on ebay for about $80 that you plug in to that port under your steering wheel that programs 3 keys for you. I tried asking the seller what happens to it after 3 keys and he couldn't really tell me. He said it probably still works. Can you do it without devices, though?

 

[Fu Manchu]

You need a suitable bidirectional scan tool. It doesn’t have to be Tech2. There are many others that can do it.

A decent mobile mechanic or a locksmith that has the gear to code a new key.

Then, there’s the other method (let’s bear in mind the perceived value of the vehicle.) of opening the key and replacing the battery. There is plenty of info here on the forum for how to do that.

*I should mention in my post where I said “start the car”, it will only start if using a paired key. It won’t matter if the battery is flat.

Also when there is a low voltage key, try putting it just off the lower centre of the windscreen. There is a small flat panel between the de-mister panels are. That is the infra red signal receiver (and sun sensor). You might get the doors to open if really close.

If that fails, do as @RiffRaffMama’s son suggests and have the key to your head. Of course there’s you laying across the bonnet, key to the windscreen, with your head on it. So that could get weird.

 

[RiffRaffMama]

So that could get weird.

Yeah, I'd probably recommend you ensure you have all the issues ironed out before you hit up your local shopping centre.

 

[chrisp]

My son swears up and down that if you touch the keyfob to your head when you press the button that it works better.

It might be that holding the fob higher off the ground (which is a ‘ground plane’) allows the RF signal to propagate better? So, nothing to do with the ’head’ as such. Get him to hold it high over his head and see if it works any better or not.

 

[Fu Manchu]

It’s because our bodies are quite good antennas.

Here’s a link that has a formula for it. A video showing Jeremy Clarkson trying it and some explanations.

Why does a remote car key work when held to your head/body?

I was trying to unlock my car with a keyfob, but I was out of range. A friend of mine said that I have to hold the transmitter next to my head. It worked, so I tried the following later that day: ...

physics.stackexchange.com

 

[figjam]

My son swears up and down that if you touch the keyfob to your head when you press the button that it works better.

Do you have to think, "Start ya bastard'' at the same time ?

I would be worried that enemies of 'Straya would be able to read my thoughts after that, and plot a nuclear strike on my house.
Or perhaps I have been reading too many doom and gloom threads on here.