Wont start. UCH / Battery / ECU ??

[AJ9939]

Hi,

Really need some help please!! I've searched, and done some of the common checks, but Car still won't start. 2003 Clio 172.

Was fine yesterday. This morning would not crank over at all. Battery 2 years old. 12.6v with no load. Down to 5v (at one point) whilst cranking it over. Consistently down to 9v with ignition on.
Tried a jump start and it would crank for 3 seconds. Then die. Same again. Next time, no crank, then it would crank over for 3 secs.

It doesn't seem possible to be a Immob issue, because it did try and crank over. Don't think Crank Sensor either. But i'm out of options now!

Is there a way of telling for sure if its UCH and or ECU related, and do these have to be bought in pairs if required? Have seen some companies repairing UCH for £70, but not ECU's...

Any help would be great!
Thanks.

 

[bloke]

don't want to state the obvious...battery

 

[Paprika123]

Does a lead from battery negative to the block make a difference?

 

[AJ9939]

I'd be pleased if it was just a Battery. I'm taking it back tmrw and (hopefully) getting a replacement one because it had a 3yr warranty. I guess if it has dead cell(s) then it's well down on cranking amps ?
Any ideas on the UCH / ECU if it's not the Battery? Anyone know which fails more often ? That lot looks complicated.....new keys....decoder ring....uch....ecu.

Thanks.

 

[AJ9939]

Does a lead from battery negative to the block make a difference?

I haven't tried that. So leave the Battery connected as normal, and run a jump lead from the Neg battery terminal to eg: Inlet Manifold ?

 

[bloke]

I'd be pleased if it was just a Battery.

9V with just ignition on answers that one:wink:

 

[AJ9939]

9V with just ignition on answers that one:wink:

Ok, thanks mate

Just doubled checked and: Ignition off = 12.6v. Ignition on (dash lights displayed) = 9.6v. Heater won't come on. Xenons won't even light with ignition off. Sidelights take it from 12.6v to 10.4v. Buzzing from left of the Air Filter housing, and ticking / clicking (not whilst trying to crank it) from behind the drivers side xenon.
So definitely pointing to Battery because UCH etc wouldn't do this ? Sorry for the simple questions! and thanks for the replies.