Abs_ Posted February 26, 2020 Report Share Posted February 26, 2020 Hello all! back with another enquiry, with cold weather here in the UK I’m coming across a problem on morning when I’m starting the car on idle the car revs are bouncing up and down slightly, the lights are diming ever so slightly too. Battery has already been replaced a while ago not more than a year with Bosch s5 so good reliable battery in. Iv noticed this happens when the heater blower is on. When I turn this off the revs stop bouncing so was wondering if anyone can help?? Once the car is fully warmed up Revs doesn’t bounce and everything runs fine it only happens on cold ? Quote Link to comment Share on other sites More sharing options...
momo Posted February 28, 2020 Report Share Posted February 28, 2020 Have you checked voltages? Bosch S5 batteries had lots of recalls recently.. Replaced mine at the beginning of 2019 because it stopped holding charge. Admittedly mine was 5 years old (and 3 months, so JUST outside of the warranty). I went with Yuasa. Quote Link to comment Share on other sites More sharing options...
coop Posted April 2, 2020 Report Share Posted April 2, 2020 (edited) Mine does this too on cold mornings, I believe it is because some or all of my glow plugs are not working [due to faulty glow plug control unit]. Does it also puff out some unburnt diesel smoke when you start it up the first time on cold mornings? If so, then you've probably got a duff glow plug control unit like me. I did replace the control unit once [quite a few years ago] and it rectified these problems. However the replacement unit only lasted about 18 months before it packed up, so I've never bothered again since. The control unit costs about £40-50 and is positioned in the most inaccessible place they could possibly have put it. Must admit I've never tried switching the heater off, I just leave the climate control in auto mode. Edited April 2, 2020 by coop missed something out Quote Link to comment Share on other sites More sharing options...
Willse46 Posted April 11, 2020 Report Share Posted April 11, 2020 This is normal behaviour according to research I have found on the net. the pulsating is due to energy being drawn from the engine for the auxiliary heater. Once the car gets up to temperature sufficiently (usually within 10-15mins) you will find that it stops. Also if you keep the temperature control at 16deg when the engine is cold the revs stop pulsing. mine’s being doing it for the last 5 years. Took me ages to find out it’s normal behaviour. Quote Link to comment Share on other sites More sharing options...
