Intermittent No Electrics

[benfl3713]

I've recently started getting a really odd electrical issue with my car. Sometimes I go to unlock the car and nothing happens, the key-fob has a small red light on it that lights up when I press it. In the end I just use the key in the door to get in.

I then put the key in the ignition and turn it and absolutely nothing happens. If I leave it for around 10-15 seconds there's a sudden click (sounds like a relay) and the electrics spring to life and the car start fine with no sign of low power on the starter.

I though it was a battery issue however when I checked the voltage it was fine.
Worth noting I recently installed a new radio unit and speakers

Any ideas what the issue may be?

[Dev]

 What kind of radio did you install. Was it used. 
 If there is a short in any electrical component it could create issues this includes aftermarket radios that draw parasitic power when the car is off.
 What I would do is disconnect the radio from the harness and see if the behavior goes away.

[paulj]

See what the immobiliser light does when you put the key in the ignition.  Its the red led in the middle of the heater controls.  It should go out immediately it recognises the key, very quick.  If yours stays on for a while it may help identify a problem.

As for the key fob unlock not working, this is a separate system which controls the alarm.  Sounds like your key might have become unregistered.  Can you lock the car with the fob or is it totally dead?  There is a how to guide on the site for reprogramming a key to the alarm (and to the immobiliser). Both add the new linked key to the list and delete the oldest entry. 4 on the alarm and more on the immobiliser, so unless you have a drawer full of keys it is worth a go. It involves lots of presses on pedals in the right order.

[benfl3713]

Hi @Dev thanks for getting back to me.

The radio I bought was from halfords: https://www.halfords.com/technology/car-audio/apple-carplay/sony-xav-ax8050d-car-stereo-with-apple-carplay-and-android-auto-342958.html?stockInventory=undefined

In theory it shouldn't draw power other then to keep the clock ticking on the radio but I will try and leave it disconnected for a bit to see if the issue stops occurring.

[benfl3713]

Hi @paulj thanks for replying

I completely forgot about the immobiliser light, I'll keep an eye on it if the issue occurs again. Perhaps it sometimes takes a while to detect the key.

The keyfob does work most of the time it's just when the car goes into the weird electrical state that it stops functioning.

[Dev]

Hi @Dev thanks for getting back to me.

The radio I bought was from halfords: https://www.halfords.com/technology/car-audio/apple-carplay/sony-xav-ax8050d-car-stereo-with-apple-carplay-and-android-auto-342958.html?stockInventory=undefined

In theory it shouldn't draw power other then to keep the clock ticking on the radio but I will try and leave it disconnected for a bit to see if the issue stops occurring.

Sony makes solid headunits even thought their units from the past were bad for sound quality they have made up for it in their newer offerings especially their ES line that they brought back.
 Anyway too much information. I would still disconnect it just to be sure to rule out any wiring issues just because it was the last thing that was done before you had this problem.

[benfl3713]

I think the issue has been resolved as it hasn't happened for a while now.

I was working on the car speakers again to change the tweeters, and when I did the big speaker on the right door stopped working. If I swapped the wires around on it, it started working again.

I didn't think it mattered which way the cables go on speakers but it seems to of made a difference as there have been no electrical issues since.

[fawtytoo]

Polarity does matter on speakers, but I don't see what that has to do with your remote key or delay with the "relay" click.

If the car does start, does it turn over slowly or fast as it should? If slowly then maybe what Dev says could be right. If it starts normally (turning over at correct speed), then I agree with paulj that it's an immobiliser issue.

How have wired up the stereo? Did you use an ISO converter, or have you cut/spliced wires?

[Dev]

As fawtytoo mentioned polarity does matter but it should have no effect except for sound issues however there is something not right based on your observations.

The speaker should work if you switch polarity in both directions. This would concern me enough to remove the head unit and do a bench test with a test speaker to see what is going on.  This could indicate a short of some sort that can effect the entire electrical system (ghosts in the machine). Usually this is the result of a failing transistor or burned out diode.

[ucb]

I had similar issues with a Volvo v50.
Turned out to be the battery terminal connector

[benfl3713]

The car does start fine and idles at the same rpm it always has in both cold and warm scenarios. I think you're right that it sounds like an immobiliser issue, or though I still have had the problem re-occur.
I got a wiring iso harness so I didn't have to do any manual wiring to the new headunit.

If the issue occurs again then I think I'll pull the lot out and test both the speakers and headunit for shorts.

The battery is fairly newish and the connectors look fine and I can easily test the voltage on the connector ends and there's no voltage difference compared to the physical battery terminals.

I think for now I'll see how it goes as it hasn't happened since I changed the speaker cables around. If it does happen then I'll do some proper testing of the different things mentioned.
Thanks everyone for the help

[fawtytoo]

How many keys do you have? Have you tried them all?

When I bought my Hyundai, of the 2 keys that came with it, one key starts the car, and the other doesn't. The one that doesn't just cranks the engine but does not fire. That's the immobiliser doing it's job correctly.

Diagnosis: faulty key.
Solution: new key.

Perhaps your key has the intermittent fault and not the car.

Also, I wouldn't ignore it. You don't want to be far from anywhere, and your car refuses to start.