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Voltage drop when AC on but no battery dash light

Help, Advice, Owners' Discussion and DIY Tutorials on S40 and V40. In this forum you'll find S40/V40-specific owners asking and answering questions on maintenance, ownership, repairs, tutorials and almost every do-it-yourself thing you can do to save money owning these Volvos.

1996 - 2004 S40
1996 - 2004 V40

Kags1969
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Year and Model: 2004 v40
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Kags1969

Voltage drop when AC on but no battery dash light

Post by Kags1969 » Tue May 21, 2019 9:50 am

I purchased a 2003 V40 for my sister and am trying to get it to a good spot where she can drive it worry free for a while. Here is the issue that I am noticing.

Using a ScanGauge2 to monitor:

~13.7 on startup drops to 12.7-13.0 during AM commute in (typically no ac)
On commute home (low rpm) 12.7 is normal unless I run the AC at which point it will drop to 11.8-12.0
I can shut off the AC and the voltage will come up to 12.2-12.4 (at idle - low rpm commute speeds)


Not sure if this is a voltage regulator issue or an alternator issue. Any sage advise?



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RickHaleParker
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Re: Voltage drop when AC on but no battery dash light

Post by RickHaleParker » Tue May 21, 2019 10:05 am

Before you start throwing money and parts at it. Clean the battery terminals and the electrical connections to the alternator. Inspect the cables to both for damage. Voltage drops under load can be something that simple.


Platform: P80 1998 C70, B5234T3, AW50-42, Bosch Motronic 4.4, Special Edition package, Plant: Uddevalla Sweden.

Platform: X40 (Nedcar) 2003 S40, B4204T3, AW55-50/51SN, Siemens EMS 2000. Plant: Born Netherlands.

Platform P2 2005 XC90 T6 Executive, B6294T, 4T65 AWD, Bosch Motronic 7.0, Plant Torslanda Sweden.
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1997 S90, B6304S, AW30-42, Bosch Motronic 4.4 - Sold

Kags1969
Posts: 2
Joined: Mon May 20, 2019 8:07 pm
Year and Model: 2004 v40
Location: TX
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Kags1969

Re: Voltage drop when AC on but no battery dash light

Post by Kags1969 » Tue May 21, 2019 10:30 am

Will do. Thanks, Chris



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