Ignition cuts out when brake pedal pressed

**goldiloxgirl** · 29th June 2015, 11:19 AM

I have searched the archives and can't find a precedent for this problem, so thought I'd ask if we have an exorcist here...or even a few ideas? My p38 had been sitting unused for a few months with the battery disconnected (brand new), but it started ok. After driving it a few miles it developed the usual ghost in the machine symptoms of radio turning itself on and refusing to turn off, gearbox fault, and eventually the instruments and ignition cut out whenever I used any electrical item such as blinker, brake pedal cabin light, headlights etc.

Alright, I know that the P38 loves voltage, and lots of it, so I put the battery on a charger overnight. Next day I could start her up but pressing the brake pedal caused the ignition and instruments to cut out. Other electrical items had no ill effect. By removing the brake switch fuse, I was able to restore normal function and drive home (a little cautiously with my eye on the rear view mirror) without brake lights.

Any ideas guys?

**Keithy P38** · 29th June 2015, 02:22 PM

I'd say that your alternator is kaput.

It doesn't explain the problem, but I think it'll go a long way towards fixing it.

Cheers
Keithy

**mtb_gary** · 29th June 2015, 02:23 PM

A quick test to see if your voltage is the problem. Try turning on the headlights. If it stops or hiccups I'd be looking potentially at another battery. Then of course there are the multiple earth connections. Definitely worth a check up.

**goldiloxgirl** · 29th June 2015, 10:42 PM

Thanks Keith and Gary. The alternator was putting in 13.3 volts when I checked and the ghost in the machine symptoms disappeared after I fully charged the battery. All that remained was the ignition and instruments going dead only when the brake was pressed. No other electrical items including headlights caused a problem, only the brakes. If there was a dead short in the brake light circuit, I would've thought the fuse would blow but perhaps it's only shorting enough to trip a relay? Or maybe there is a ghost inside the BeCM.

But I know one thing...brakes are suppose to stop the car _ not the engine!

**TheTree** · 30th June 2015, 08:17 AM

Hi

I would suspect an earth connection, the one behind the side panel where the bonnet release is.

Also worth checking the under bonnet ones

Steve

**Rupert Prior** · 30th June 2015, 09:13 PM

if you are around the area of Bexley or up to Padstow, i can have a quick free look at it (rover electrics is what i do for a living) ring me 0421509083 regards Rupert

**d2dave** · 30th June 2015, 09:32 PM

Originally Posted by Rupert Prior

(rover electrics is what i do for a living

You must be a very busy person

**Rupert Prior** · 30th June 2015, 10:30 PM

not so much now, values are low, parts are expensive, even some sports are beyond economic repair.

**Ghind** · 1st July 2015, 10:47 AM

Now that you've fully charged the battery, start the car, turn the rear window heater on, high beam headlights on and heater fan in max. Hold the engine at 2000rpm. What voltage are you getting across the battery then?

Is it ok to post a link to a post I wrote on another Range Rover site about how to diagnose this?

**glenhendry** · 1st July 2015, 07:47 PM

Originally Posted by Ghind

Is it ok to post a link to a post I wrote on another Range Rover site about how to diagnose this?

Your electrical sticky has helped so many over the years, I certainly hope it is ok to link to from here...

Thread: Ignition cuts out when brake pedal pressed

Thread Tools

Ignition cuts out when brake pedal pressed

Bookmarks

Bookmarks

Posting Permissions