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MG Midget and Sprite Technical - Modern Electrics (NMC)

My daughter rang me to come and help. Her partner's car is a Golf V5 which was refusing to start.

Turning the ignition on, the dash warning lights all come on, it goes through its self-check as normal. Turning the key to operate the starter all dash lights go out. There is no click from the starter solenoid. I assumed from this that there is a dead short on the starter circuit.

On releasing the key from the starter position, there is a rapid clicking noise, all the dash lights, interior lights etc flash rapidly. This continues for about 20 seconds before it settles down to just the normal steady dash warning lights.

But the same seems to happen when, with ignition on, I turn on the main headlight switch. Everything goes off until I switch the lights of again, when it then goes through the berserk flashing dash lights routine for 20 seconds.

So I guess there is a short somewhere, but not the starter motor. I tried disconnecting and reconnecting first the battery and then the ECU but no improvement.

So how would I go about isolating the problem?

Guy
Guy Weller

'Modern' cars. Doncha jus luv 'em?

Jesting aside, I had similar symptoms with my (not so modern) Astra. Transpired that it was the battery that suddenly died (one minute running fine, the next - quirky non-starting symptoms).

Further investigation showed that one of the battery's internal cells suddenly went short circuit which gave enough battery terminal voltage to power the dash warning lights, but as soon as any serious load was put on the battery (starter solenoid, starter motor, main lights) very weird things happened.

My advice to you: get the battery checked before you do anything else.
Andy Hock

Ah, I did think of trying the jump leads but had convinced myself that here was a short so didn't try that.

Guy
Guy Weller

I think its the battery also!!
Mick - trying to sort the wiring

yep id go with battery , most modern batteries go that way now ok ,ok ,ok , then buggered , no in between
Darren 2 litre frogeye

We left the car parked where it was last night but will go back to it today. What threw me was all the lights going berserk and rapidly flashing off and on like that. Made it seem like something much more serious than just a flat battery!
Why couldn't it just make that familiar "clunk" of the starter failing to turn and dim the ignition light like any proper car?

Guy
Guy Weller

Yep, and why can't the oil just leak slowly out the rear seal? Cars these days, not what they used to be!

My bet's on the battery.
R S Amos

And if it had a dead short in the wiring, I think you would have seen or smelled smoke. If the battery is internally shorted, it may not respond well to jump starting, and so will need a replacement to check it out.

Charley
C R Huff

Guy,

had something similar on an Alfa 156 Selespeed which wouldn't engage gear - turned out to be a dodgy battery, modern batteries just seem to be fine one day and dud the next.
Jeremy
Jeremy 3

My vote's also on the battery. I was having similar issues with my '98 GTI VR6 recently, with things being great one day and a non-starter the next, with fluttering lights, etc. I took it to our local garage, who diagnosed a bad battery. The dumb part is that I could have easily thrown a new battery in there myself, but decided to play things safe and get an official opinion. So I ended up spending a lot more than I needed to just to find out something I already suspected. Argh...

-:G:-
Gryf Ketcherside

Could also be poor connection on battery, as well as battery not up to the job of turning the starter.

Brown-outs confuse the ECU which has to be re-set probably by a watch-dog timer figuring it needs a warm reboot. All the lights, relays etc are controlled by the ECU, so everything appears to go haywire for a mo.

A
Anthony Cutler

And the answer is......

Battery!

Thanks everyone!.

It jump started immediately (off the Sprite) and behaved normally except it now has a warning light about the ABS which may sort itself, or not.

Checked with a meter - when running volts across the battery terminals were 14.27 so the alternator is working fine. The quiescent state of the battery showed only 9.8 volts so it certainly looks like a dead cell. Couldn't check cranking volts because even after a bit of a run there wasn't enough power there to do any cranking.

Replacement battery will be purchased!

Guy
Guy Weller


A (Slightly related) word of warning -

Be very careful about jump-starting from moderns. I have a friend who have completely kippered his electrics by offering a jumpstart to someone else.

It was a Renaultsport Clio which had a whole host of bizarre symptoms like the self-leveling headlights adjusting up-and-down-and-up-and-down, random dashboard warnings, cutting out when it hit the rev limiter. Took it to the garage and the first thing the mechanic said was 'you haven't given someone a jump start, have you?'. He never really sorted the problems and ended up selling it...

It was there somewhere in the manual - don't give jumpstarts from this car - but who ever reads the manual cover to cover?

beware!

Mark
MarkH1

I bet your Sprite was right chuffed at the opportunity to jump-start your "modern"! I know my midget was just tickled pink a couple years ago when it was the only car in the harem that started in the bitter cold we were having ;-)

Since then I have replaced the battery on the VW GTi VR6 with a new Interstate unit and it works better than the original EVER did.

9.8V means that one of the cells is completely dead and the remainder are none too healthy either.
David "I am not yet dead" Lieb
David Lieb

David, funny you should comment on that.
I was parked in front of the VW and getting the jump leads out of the boot when a chap walked past and offered to help push it. I said no its OK, and he stood by and watched as I hooked up the jump leads. His expression when I first started the Sprite and revved it up a bit before we started the VW was priceless! He thought it was really funny when he realised his mistake.

Battery has been replaced and VW now fully operational again.
Guy Weller

Guy,
That IS priceless!
David "too bad you don't have the video" Lieb
David Lieb

a good job I was elsewhere innit?

what would I have said?

you guessed it... *

well done for sorting it.





* no, not condenser!
Bill sdgpm

At the time, the thing that threw me was the way the lights all flashed on an off. Gryf called it "fluttering" which is a very apt description. It made me think that there must be something drastically wrong with the on-board computer ECU thingie. And those things are expensive to replace!
Guy Weller

Guy,
What you were seeing was the resulty of inadequate voltage to the ECU. It kept trying to run the power-on self-test (POST), failing, and starting over. Had you simply connected the jumper cables and turned the ignition on, it would have looked normal. Fancy electronics tend to be very sensitive about voltage level. Since you had a dead cell rather than merely a tired battery, your voltage was not high enough to actually operate the electronics. With the more usual tired battery, the current is inadequate to handle loads like lights and starter, but the voltage is there up until you attempt one of those big tasks. Therefore the symptoms on a "modern" are very different from one scenario to the other.
David "low wattage" Lieb
David Lieb

This thread was discussed between 12/06/2009 and 17/06/2009

MG Midget and Sprite Technical index

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