Twice this last month I have gone to the rescue of a dead unit,well,if drivers think they can run all the toys in the cab these day’s without keeping batteries charged,silly billy’s.Neither driver knew the secret of jump starting today’s modern pieces of electronic junk which we are all driving.ECU’s,the electronic control units that control just about everything have to be protected from the sudden surge of 24 volts and this is done by switching on all the lights on the DEAD unit BEFORE jump leads are attached.Now all you remember this as ecu’s cost about £1000 each to replace,todays handy hint making you all more pro.Ricki,best you feature this in T&D,could do a whole page on jumping I expect,you could even feature the $%^ mechanic who actually burnt out 3 ecu’s x £1000,nice one.
getting a ‘Jump’ on the road ?
OH !! - I thought this was going to list houses of ill repute across the UK 
ROG:
getting a ‘Jump’ on the road ?
OH !! - I thought this was going to list houses of ill repute across the UK
me too and it too would be great if it had its own section in T+D!!
Armagedon:
ECU’s,the electronic control units that control just about everything have to be protected from the sudden surge of 24 volts
Absolute rubbish. What do you think happens when you turn on the ignition key?
For the benefit of Conor…switching on the ignition is merely bringing into play a power source which is already in place…attaching jump leads is introducing an external source but you do it your way…at a price or go and ask your pro mechanics what they do.
turning on all the lights and gadgets would actually cause a power surge due to the massive amount of draw caused by everything been switched on , remember electricity is not pushed its pulled so if everything is switched on it will pull a massive amount of electricity , just like when the power comes on after a power cut at home everything goes bright for a few seconds.
There is a right way and a wrong way to jump start a truck. I always turn off both battery isolators before connecting the leads, and only three clips should be connected to the battery set, the fourth and final connection should be to an earth, away from the battery set, on the truck which is giving the jump start, to minimise the risk of the stricken batteries exploding when the connection is made.
Harry Monk:
There is a right way and a wrong way to jump start a truck. I always turn off both battery isolators before connecting the leads, and only three clips should be connected to the battery set, the fourth and final connection should be to an earth, away from the battery set, on the truck which is giving the jump start, to minimise the risk of the stricken batteries exploding when the connection is made.
I always thought that the final connection to earth was to the truck receiving the jump rather than the giver. 
and i thought that every truck on the road for the last 15 or so years had a battery guard of some sort on it . 
I always thoght the best way was to turn off the battery masterswitch first, then connect jump leads, turn back on master switch then start up,.
Turning on the ignition only sends a low current to the ignition relay which then goes to the solenoid.
Any truck fitted with a computer should be jump started with care, either using a surge protector or at least turning on the headlights before connecting the leads as HM suggested
macplaxton:
Harry Monk:
There is a right way and a wrong way to jump start a truck. I always turn off both battery isolators before connecting the leads, and only three clips should be connected to the battery set, the fourth and final connection should be to an earth, away from the battery set, on the truck which is giving the jump start, to minimise the risk of the stricken batteries exploding when the connection is made.I always thought that the final connection to earth was to the truck receiving the jump rather than the giver.
I may be wrong, but I’m given to understand that the danger is that the electrolyte in the stricken batteries may be frozen and this is what causes the risk of explosion when current is applied, as the electrolyte in immediate contact with the plates boils. It is a sudden expansion, rather than a fuel-based explosion. Sulphuric acid fumes are not flammable, and even if they were this would cause a flash above the batteries and would not cause them to burst open.
I would be interested to know the definitive answer though.
al_P:
turning on all the lights and gadgets would actually cause a power surge due to the massive amount of draw caused by everything been switched on , remember electricity is not pushed its pulled so if everything is switched on it will pull a massive amount of electricity , just like when the power comes on after a power cut at home everything goes bright for a few seconds.
The force which pushes the electrons causing them to swap atoms orderly and in the right direction is a potential difference placed across a conductor. This force ( electrical pressure ) is more commonly known by its unit of measurement VOLTAGE.
dave:
and i thought that every truck on the road for the last 15 or so years had a battery guard of some sort on it .
Yes, but you have to remove it before connecting the jump leads, otherwise you won’t see where to connect them to. 
Blimey, my taxi is here already… 
Sorry Dave, I couldn’t resist… 
dieseldave:
dave:
and i thought that every truck on the road for the last 15 or so years had a battery guard of some sort on it .
strange as the mechanic {from mercedes} who came out to jump my actros off didnt do any of the above, he just hooked me up and turned it over, no headlights or anything like that
if you read the manuals you’ll see what armagedon says is correct…oh silly me iforgot …not only are you lot trukers you’re men as well (well most of you) the manuals will be chucked as soon as the wagons done 10 kms
Chaversdad…a Mercedes mechanic…please buddy,excessive laughing I am told will endanger my health…Mercedes do not have mechanics they have fitters and there is a massive difference which is why he did not do as I have stated.
Positive of flat battery to positive of good - then earth of good battery to a good CHASSIS earth on the dead vehicle - start & run for about 5 minutes at 1000 to 1300 rpm - then turn on the lights and allow the vehicle to idle for about a minute - take off the leads starting with the chassis earthed negative lead - then turn the lights off - ECU’s safe 
Steve
Armagedon:
Chaversdad…a Mercedes mechanic…please buddy,excessive laughing I am told will endanger my health…Mercedes do not have mechanics they have fitters and there is a massive difference which is why he did not do as I have stated.
maybe, but the point i,m trying to make is there was no almighty bang or ecu,s being fried, the truck was exactly normal, and i have to admit on the twice i,ve jumped it off {after xmas hols} i,ve just pulled the forklift up next it and jumped it straight off with no probs at all, so maybe i was just lucky 3 times