Menu toggle

In-car voltmeter

vincematthews

vincematthews

Member
I've been doing some work to try a get round the in-car voltmeter reading low especially when the battery is under load. Using a DMM to check at the battery terminals showed the the voltage under load was an acceptable 13.5 V. Using the same DMM in place of the in-car voltmeter confirmed an unacceptable voltage drop (taking into account the difference between the two voltmeters). It would be nice to be able to look at the in-car voltmeter and have it confirm everything was OK.

Has anyone tried rewiring the in-car voltmeter to more directly read battery voltage? Obviously it would have to be on a switched/fused circuit. I'm just wondering where is the best place to connect. Thanks
 
I had the same issue with mine. After cleaning all the earths and from memory the voltmeter gets its power from a thin black wire which start from a pin on the fuel pump relay. Once I cleaned that up the voltage was far closer to what I was seeing at the battery. The wiring diagrams in Haynes manuals gave me what I needed to trace it back

Good luck
 
Thanks Russ, I'll check that out. There is still a 0.3V difference between the DVM and the VDO voltmeter at around 12V, do you know if it's possible to adjust the VDO voltmeter?
 
I don’t know. Given the volt gauge is going to be 40 years old or so I just accept it’s not 100% accurate but gives an idea on what the battery\alternator is doing and if I need to worry.
 
You must log in or register to reply here.

Posts made and opinions expressed are those of the individual forum members

Use of the Forum is subject to the Terms and Conditions

Disclaimer

The opinions expressed on this site are not necessarily those of the Club, who shall have no liability in respect of them or the accuracy of the content. The Club assumes no responsibility for any effects arising from errors or omissions.

Porsche Club Great Britain gives no warranties, guarantees or assurances and makes no representations or recommendations regarding any goods or services advertised on this site. It is the responsibility of visitors to satisfy themselves that goods and/or services supplied by any advertiser are bona fide and in no instance can the Porsche Club Great Britain be held responsible.

When responding to advertisements please ensure that you satisfy yourself of any applicable call charges on numbers not prefixed by usual "landline" STD Codes. Information can be obtained from the operator or the white pages. Before giving out ANY information regarding cars, or any other items for sale, please satisfy yourself that any potential purchaser is bona fide.

Directors of the Board of Porsche Club GB, Club Office Staff, Register Secretaries and Regional Organisers are often requested by Club members to provide information on matters connected with their cars and other matters referred to in the Club Rules. Such information, advice and assistance provided by such persons is given in good faith and is based on the personal experience and knowledge of the individual concerned.

Neither Porsche Club GB, nor any of the aforementioned, shall be under any liability in respect of any such information, advice or assistance given to members. Members are advised to consult qualified specialists for information, advice and assistance on matters connected with their cars at all times.

Porsche
Lockton
Pirelli
Officially approved
Oracle Finance
WEX Esso
Collecting Cars
Archant Dialogue
Back
Top