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Member Since: 21 Mar 2014
Location: Suffolk
Posts: 2971
 
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| Alternator slow to respond to load change - is that normal? | |
I know the Pumas have an ECU controlled "smart" alternator, which means it does things like taking a few seconds to get going after the engine starts so if you turn the headlights on after starting the engine they're dim, then suddenly get brighter.
I've noticed when I switch on high current loads that the voltage drops before recovering a few seconds later. At first it was anecdotal, like if you start up the headlights and wipers with the door open the interior light dimmed and then came back. Then I saw it a bit more with the Ultraguage fitted, voltage typically sits about 14.0-14.2 but if you put the lights on it drops to 13.6 for a second or two.
I've now realised that's why my compressor sounds funny when it starts. With the engine running, you turn on the compressor, it starts and runs then after a few seconds speeds up. Looking at the Ultraguage, it's reporting that the ECU voltage drops from 14V to 11.5V for a few seconds, then rises back up to 14V again.
It's not a problem with the alternator not coping with the load, it's a problem with the alternator not picking up the load quickly.
Is that normal? I don't think it's a problem, just a bit odd!
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17th Jan 2016 1:28pm |
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