2.5L Automatic Petrol Connoisseur Tourer non-start.

brds · 30th December 2022, 13:47

Battery was flat yesterday (3.6V) so I tried to jump start it with a spare battery. Alarm horn went off and indicators flashed. Couldn't shut them down and car wouldn't start so disconnected the jump battery.
Left car battery connected and on charge overnight with an automatic level sensing charger. - N.B. I've never had a problem charging it like this before and it's now 13V.
Today: Dashboard ignition sequence lights look OK and the starter motor turns OK but it doesn't start so the attempted jump start has obviously damaged something.
Other symptoms: Doors won't unlock via key remote or centre button but the indicators flash. (Got in with drivers door key).
No trip mileage shown and the dashboard gear-shift indicator shows (ER).
My initial thoughts are with an immobiliser or BCU problem.
I'll use my other car, so not desperate but any ideas to save time would be welcome before I start looking with TOAF and checking all the fuses - it's cold outside.
Bob

SD1too · 31st December 2022, 10:27

Quote:

Originally Posted by brds

Battery was flat yesterday (3.6V) ...

Hi Bob,

Unless your car has been standing unused for many months, 3.6v suggests an internal battery fault. If so, connecting a second battery in parallel with it is likely to drag down its voltage and give you unexpected results.

Before you go any further I would say that it's time for a new battery and take it from there.

Simon

dave lincs · 3rd January 2023, 06:58

Now that you're battery is properly charged I would start by checking the 150amp Megafuse as it will have blown which is in the under bonnet fuse box

brds · 5th January 2023, 12:46

Many thanks for the ideas guys & sorry for tardy reply. Weather's better today so I've just checked the car.
Battery is fine, only dropped to 12.6V in five days and cranks engine OK.
Dave, you were spot-on with the 150A Mega Fuse, it is Dis which is a worry as I've never had something as drastic as that before.
Assume you've had the same problem so do you know why it happened and is there anything else I should check before attempting to replace it.
regards,
Bob

30th December 2022, 13:47	#1
brds Regular poster Rover 75 Tourer Join Date: Jun 2010 Location: Haverhill Posts: 36 Thanks: 4 Thanked 6 Times in 4 Posts	2.5L Automatic Petrol Connoisseur Tourer non-start. Battery was flat yesterday (3.6V) so I tried to jump start it with a spare battery. Alarm horn went off and indicators flashed. Couldn't shut them down and car wouldn't start so disconnected the jump battery. Left car battery connected and on charge overnight with an automatic level sensing charger. - N.B. I've never had a problem charging it like this before and it's now 13V. Today: Dashboard ignition sequence lights look OK and the starter motor turns OK but it doesn't start so the attempted jump start has obviously damaged something. Other symptoms: Doors won't unlock via key remote or centre button but the indicators flash. (Got in with drivers door key). No trip mileage shown and the dashboard gear-shift indicator shows (ER). My initial thoughts are with an immobiliser or BCU problem. I'll use my other car, so not desperate but any ideas to save time would be welcome before I start looking with TOAF and checking all the fuses - it's cold outside. Bob

3rd January 2023, 06:58	#3
dave lincs Posted a thing or two Rover 75 Saloon Join Date: Mar 2014 Location: Louth Posts: 1,450 Thanks: 380 Thanked 986 Times in 476 Posts	Now that you're battery is properly charged I would start by checking the 150amp Megafuse as it will have blown which is in the under bonnet fuse box

5th January 2023, 12:46	#4
brds Regular poster Rover 75 Tourer Join Date: Jun 2010 Location: Haverhill Posts: 36 Thanks: 4 Thanked 6 Times in 4 Posts	Many thanks for the ideas guys & sorry for tardy reply. Weather's better today so I've just checked the car. Battery is fine, only dropped to 12.6V in five days and cranks engine OK. Dave, you were spot-on with the 150A Mega Fuse, it is Dis which is a worry as I've never had something as drastic as that before. Assume you've had the same problem so do you know why it happened and is there anything else I should check before attempting to replace it. regards, Bob