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![]() | Home > Technical > HDC Fault - car won't start |
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Boycey Member Since: 10 Mar 2013 Location: Midlands Posts: 97 ![]() ![]() ![]() |
I often get an 'HDC fault' message on starting on very cold mornings but it disappears quickly, and it's never failed to start.
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pab Member Since: 28 Aug 2012 Location: Now in Mid-Wales Posts: 2007 ![]() ![]() ![]() |
I suspect the HDC Fault message may be a symptom rather than the cause - HDC faults wouldn't usually prevent the car from starting aiui.
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jonellis69 Member Since: 19 Mar 2013 Location: Bristol Posts: 2 ![]() ![]() ![]() |
Thanks for the advice chaps.
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pab Member Since: 28 Aug 2012 Location: Now in Mid-Wales Posts: 2007 ![]() ![]() ![]() |
The Start Control Unit is in the dash - it's where the key docks. This is presumably what the dealer means when he says he's replaced the start button? In which case there's a good chance that was the cause of the problem. Fingers crossed! |
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JST Member Since: 01 Nov 2011 Location: Lizant Posts: 1098 ![]() ![]() ![]() |
....or it is simple matter of the battery on it's way out. John
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oldgeezer Member Since: 09 Apr 2011 Location: Wiltshire Posts: 1302 ![]() ![]() ![]() |
HDC fault is triggered by a battery voltage drop , so when a heavy demand is on the battery, or its not top notch then HDC disabled appears during start up !
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michal969 Member Since: 01 Sep 2012 Location: Semily Posts: 185 ![]() ![]() |
Agree with oldgeezer
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oldgeezer Member Since: 09 Apr 2011 Location: Wiltshire Posts: 1302 ![]() ![]() ![]() |
Yeah i had over 3.5 volts on cranking across the earth !
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Boycey Member Since: 10 Mar 2013 Location: Midlands Posts: 97 ![]() ![]() ![]() |
Can you explain this test in more detail please? Surely if you connect between the block and negative terminal you're just checking continuity? How can you be measuring voltage without a positive side to the circuit? I don't doubt for a second I'm failing to understand, & would be very interested to know better. Cheers |
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Pete The Biker Member Since: 30 Sep 2012 Location: Leicestershire Posts: 77 ![]() ![]() |
If you have the test meter set to read volts, you are not testing continuity, you are testing for a voltage differential from one end of the earth strap to the other. This differential would be caused by a poor connection through the earth strap, creating a resistance.
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Boycey Member Since: 10 Mar 2013 Location: Midlands Posts: 97 ![]() ![]() ![]() |
Thanks, Pete. I think I understand now. THe test would be (reading volts) first across positive and negative of the battery, and compare that with reading across positive battery terminal and cylinder block when cranking? I can understand that would give a voltage reading. Maybe I misread the original, but it said with the multimeter set to volts, connect one lead to neg terminal of the battery and the other to the block. I'm right in thinking that wouldn't give a voltage reading aren't i? Cheers Boycey |
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EYorkshire Member Since: 18 Nov 2010 Location: (!) Posts: 4392 ![]() |
Boycey, You are right in thinking if you put the probes across negative battery post and the other to engine block you SHOULDN'T get a voltage reading and if you don't then all is good |
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Boycey Member Since: 10 Mar 2013 Location: Midlands Posts: 97 ![]() ![]() ![]() |
Ah!! The coconut goes to 'E' Yorkshire. NOW I understand. Thanks very much ![]() A day wasted if you don't learn anything, so delighted to pick up tips here. ![]() |
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oldgeezer Member Since: 09 Apr 2011 Location: Wiltshire Posts: 1302 ![]() ![]() ![]() |
but you need to watch the needle for voltage when the starter engages so you need someone alse crancking it and it needs to be cold and left overnight before you try it
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