R129 jump start

[truck71]

Having not driven the car for three weeks battery is flat, when I call the aa to start it what do I need to tell the chap?

[ZX10R NIN]

Nothing apart from it won't start lol

[mickyveloce]

I wouldn't jump start a 129; too many things to get fried in the event of a surge. Charge the battery, or stick a new one on!

[BrightonIMD]

Certainly don't jump start it. Take the battery out and charge it.

A guy who was looking after my car jump started mine after being sat for 6 months the other year. I told him specifically not to do this, as it can damage the ECU. He did anyway and the roof ECU module blew up. It cost him £900 for a new one! Be careful!

[truck71]

Cheers, I guessed as much. I'll invest in a charger, does anyone have any recommendation or do i just get a £30 one from a motor factor?

[harrykul]

I use the Ctek MXS 5.0 on my SL- any of their products seem well regarded.

[env]

I have a (sort of) related question....

I bought the SL500 that was on sale at Speedwell a few months ago now, the battery keeps flattening itself, will only stand for 2 days.

I was trying to work out why and noticed that when left you can hear the interior fan running very quietly, this must be the culprit.

Any advice on why the fan might run when everything is turned off and locked down? Quite confusing!

Thank you for any help in advance.

[V12 AMG]

mickyveloce said:

I wouldn't jump start a 129; too many things to get fried in the event of a surge. Charge the battery, or stick a new one on!

When you fit a new battery, you will experience exactly the same type of surge as when you jump start it.

I've personally jump started 100's if not thousands of MBs and never had an issue.

Procedure is simple, connect leads between cars with engine off. Start other car and leave for a couple of minutes before attempting to crank the car with the flat battery. Larger leads will help.

If you connect small leads whilst the other car is running then you will get voltage spikes.

If you crank it over without giving it a minute or 2 you can fluctuate from 14V down to as low as 10V. This fluctuation is where it becomes dangerous.