Richardtr3a Posted March 3, 2020 Report Share Posted March 3, 2020 I have my son's VW Passat. I will be fitting the new battery tomorrow. If I disconnect the existing will I lose any of the settings, mileage etc. I could run two cables from the new battery to the car before disconnecting the old battery, so that the supply is constant I am hoping that it as simple as fitting a new battery to my 3A Any advice would be helpful. Richard & B. Quote Link to post Share on other sites
BlueTR3A-5EKT Posted March 3, 2020 Report Share Posted March 3, 2020 Take it to Halfords If it goes wrong you can shout at them. Peter W Quote Link to post Share on other sites
Peter V W Posted March 3, 2020 Report Share Posted March 3, 2020 Hi Richard, Read the handbook, should give details. Quote Link to post Share on other sites
Waldi Posted March 3, 2020 Report Share Posted March 3, 2020 Richard, in most cases it will reset an internal memory, like for errors detected in the ECU system. But milage will not be affected. If there is a radio with a pin code, I would install a temporary feed for belts and braces. If it is a more modern version car like less than 10 years old, I would certainly do as Peter recommends above. Waldi Quote Link to post Share on other sites
peejay4A Posted March 3, 2020 Report Share Posted March 3, 2020 You’ll need to reset the electric windows. Quote Link to post Share on other sites
G Denson Posted March 3, 2020 Report Share Posted March 3, 2020 What ever you do Don’t just disconnect the battery. You MUST connect up another one in tandem so there is a constant supply of current. If you don’t you could loose some of the stored information. Halfords seems to be a good idea so if it goes wrong you can blame them Good luck Cheers Gordon Quote Link to post Share on other sites
Grahamgl Posted March 3, 2020 Report Share Posted March 3, 2020 Will Halfords fit a battery they have not supplied? Graham Quote Link to post Share on other sites
Richardtr3a Posted March 3, 2020 Author Report Share Posted March 3, 2020 It looks as if I was sensible to start this thread. I already have the battery, delivered by Lincon batteries, who make a very good replica for the TR3 battery. So I think I will have to find the jump leads and take some care next time it stops raining. What would be a smaller cable that would work? Thanks Richard & B. Quote Link to post Share on other sites
peejay4A Posted March 3, 2020 Report Share Posted March 3, 2020 (edited) What’s the year of manufacture? If it’s recent then you’re unlikely to have a problem. Settings, mileage etc will be stored in flash memory. If it’s an automatic the gearbox adaptations might reset to default but that’s no problem as it will relearn. As I said before the windows will need resetting so that the safety sensors work. Usually you fully open a window and keep the switch operated for a few seconds. Then close the window and hold for a few seconds. Repeat for all the windows. You don’t need a parallel battery. Edited March 3, 2020 by peejay4A Quote Link to post Share on other sites
ianc Posted March 4, 2020 Report Share Posted March 4, 2020 Modern cars have a socket into which a temporary supply can be plugged in order to keep the vehicle's brains alive. In my Citroen, it's under a flap in the cubby/elbow rest between driver and front seat passenger. Halfords (and other companies) just carry battery with connected adaptor, and plug this into the socket, then disconnect and replace the car's battery. Ian Cornish Quote Link to post Share on other sites
Richardtr3a Posted March 4, 2020 Author Report Share Posted March 4, 2020 This is a 15 tear old VW Passat and has covered a high mileage, but runs well. Today it was dry weather until I opened the bonnet. It was clearly going to rain soon. So I disconnected the battery and removed it and then fitted the new one from Lincon Batteries. The operation was swift and went well. No lost spanners in the engine bay. I went to start the engine and it worked immediately. The only difference was the clock which was easy. I did try the windows as suggested and the radio did not have a code. However it is the same as my TR3a. Once you have fixed some problem it seems to run better, or is it just in the owners imagination. The VW is now smoother when starting from cold. Thanks for all the advice. Richard and B. Quote Link to post Share on other sites
HSM Posted March 5, 2020 Report Share Posted March 5, 2020 All Volkswagens retain the codes in the ECU you can change the battery without any extra precautions Harvey S. Maitland Quote Link to post Share on other sites
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