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10th January 2019, 18:13 | #1 |
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75 model car Join Date: Apr 2011
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Charging system
My brother in law called me today to ask about a battery problem. I popped round with a voltmeter after he had charged the battery and taken the car for a good run. The reading was 12.83, after starting the engine it went to 13.88, but when the revs were increased the reading remained static, instead of inreasing to 14.3. Does this mean the alternator is not charging?. I tested my own vehicle and once the engine was started and revs increased it went sraight to 14.3v.
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10th January 2019, 19:02 | #2 |
Doesn't do things by halves
Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model. Join Date: Mar 2007
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Rich,
With my own cars I have noticed some variation in the charging voltage. 13.88 volts is fine. Simon
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11th January 2019, 07:25 | #3 |
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13.8 will be ok Rich, but it depends how many on board systems the car has, obviously 14+ would be better.
It may be the first sign that the alternator is wearing out.
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11th January 2019, 18:12 | #4 |
SERVICING AND DEALER DIAGNOSTICS
MG ZT CDTI 135 + & MGZT CDTI AUTO 160 & ROVER 75 TOURER CDTI 160 TROPHY YELLOW Join Date: Aug 2013
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Andy is spot on 13.8 can soon drop when on idle with lights/heating/stereo/and wipers running, I would suggest turning on all the accessories and then measuring it at idle.
I too would rather see 14+ at idle Mick
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11th January 2019, 18:30 | #5 | |
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Quote:
The lower voltage could indicate the battery was nearly fully charged. The internal resistance of the battery INCREASES as it charges. Could be making that multi-meter voltage drop slightly. Also the voltage regulator could be the limiting factor due to a slight change in which its internal components are working. However 13..88 volts will keep the battery charged in normal use of the car.--- Don't forget that you will only get an accurate voltage reading from the battery several hours after it has come off charge. Immediate readings are never accurate.--- |
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13th January 2019, 18:47 | #6 |
This is my second home
R75 Saloon. Join Date: Feb 2009
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Richard.
How did you get on with that problem you asked a question about ??? |
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