Electrics - fuse 28

Fri Oct 28, 2011 8:45 pm

Hello.

I've blown a 30amp fuse (no. 28 ) by plugging a small electric car fan heater into my cigarette lighter socket.

When I try and replace the fuse with a new one, it sparks and blows as I push it into place (ignition is off).

The radio stopped working when the fuse blew, but not sure why as the radio fuse (no. 12) is OK, and the instruments continued to work.

Now I can't lock the car with the remote key fob (Sigma alarm), and can't start the car as the immobiliser has kicked in and the horn sounds when I turn the key. I guess the alarm runs off the same circuit...

If power is still running through fuse 28, could something in the cigarette socket be stuck? Maybe if I disconnect the battery first I can get the fuse in place? Can't see to do much tonight and have run out of fuses, so will try and fix it tomorrow.

Any thoughts (apart from not using crappy heaters again)? Thanks!

Fri Oct 28, 2011 9:12 pm

ahhh...fuse 28...

i,ve had this problem twice before... caused by a metal object sliding underneath the ashtray and shorting out the red/yellow cigar lighter feed.

remove the 2 screws and have a look under the ashtray cover

Fri Oct 28, 2011 9:32 pm

Ahh..nice, thanks! Will give it a go tomorrow...

Fri Oct 28, 2011 10:45 pm

Look into the lighter socket from the top first. Quite common for a bit of metal foil or a pin/clip to find its way in there.
Also quite common for aftermarket ICE installers to take their live feed from 28.

Sat Oct 29, 2011 11:42 am

I checked the lighter socket and as you suggested, there was a tiny piece of metal foil stuck underneath. I removed it and was then able to fit a new fuse 28 without it blowing. I closed the doors and bonnet, pressed the alarm fob and the doors locked / alarm set.

So far so good.

I unlocked the car with the fob, tried to start the engine, and it started but the horn sounded continuously at the same time, (the alarm has it's own seperate siren).

I ended up removing the entire horn from the engine (I couldn't disconnect the wires as they had rusted on). Then I started the car....no problems.

There is another seperate issue...when I unlock the car with the alarm fob, I have 10 seconds to start it before the immobiliser kicks in. If i wait too long, I have to press the button on the alarm fob to switch off the immobiliser so I can start the engine.

Now, when I try that, the immobiliser turns off, but the central locking triggers, locking me in. I can lift the door lock to get out, but it wasn't doing that before this whole fuse thing started.

So, I can't use the horn, and I think I might have fried the electrics =(

But at least i'm back on the road.
Thanks for your help!

Sat Oct 29, 2011 4:51 pm

There is probably an internal battery in your alarm, which was just clinging to life while being charged by the main battery. With fuse 28 blown, it no longer had this supply available, and has now died.
Any idea on the make/model of this alarm?

Sat Oct 29, 2011 5:22 pm

I think i've fixed it.

I bought some new connecters for the horn and refitted it. Now I have a two tone horn that works as it should. I'm too embarrassed to say why it was sounding when the engine was started...let's just say...'dumb user error'!

The central locking problem seems to have corrected its self.

The only thing that doesn't work (and this is a completely seperate issue) is that there is no hot air entering the car when the heater is on. Apparently the heater pipes on the matrix are hot, and I dropped the glove compartment to check that the blade fuse was OK (there were two, an 8 amp and a 15 amp, and both were OK).

I'll search the forum for heater answers before I post again.

Cheers...

Sat Oct 29, 2011 5:47 pm

re: heater. I remember it working before the water pump was replaced. Could it be possible that the garage reconnected some pipes incorrectly? Not sure what is involved with a water pump replacement, and my Haynes manual doesn't cover M42 engines.