Talk Morgan

Voltmètre or Ampmeter?

Posted By: Toucan

Voltmètre or Ampmeter? - 30/12/19 10:15 PM

Hi all,
On my dashboard l have an indicator posted as a Volt meter round shaped, last on the right side.
On the wiring diagram for 1981 4/4 it is suposed to be an Ammeter.... Needle on 14 (+++) nearly all the time. is this a real Voltmeter, and wiring diagram wrong, or an Ammeter indicating the charging status poetically posted as Voltmeter by the factory? wine
Has anybody got a wiring diag with a Voltmeter? confused2
Posted By: Image

Re: Voltmètre or Ampmeter? - 30/12/19 10:36 PM

An ammeter should have brown and brown/white wires going to it and be between your alternator and solenoid.... It should also read both ways from the centre + and -

A voltmeter goes from something to earth, reads one way, and 14 ish volts would be good high charging volts for your battery

Try turning your ignition on... If the meter comes up to 12/13 without the engine running it's a voltmeter (and may rise to 14+with the engine running)

An ammeter will sit (pretty much) with the ignition turned on.... Go negative if you put the headlights on.... Go really negative when you hit the starter... And come back up when it's running (pretty much to the middle if your batteries good or into the plus if it's putting back what you just took out)


K

PS... welcome Toucan... I also have a crossflow engined car.... Gradually being reduced to a chassis before coming back better than ever hopefully
Posted By: Eddie Cairns

Re: Voltmètre or Ampmeter? - 30/12/19 10:42 PM

Yes it is thought for normal use the voltmeter confirms that the electics are working.

A true ammeter in the circuit is a possible failure point in the electrical system and with modern alternator equiped cars since the late 1970's there is no advantage to be gained by having an ammeter.

Only a place for things to go wrong.
Posted By: +8Rich

Re: Voltmètre or Ampmeter? - 30/12/19 10:46 PM

As has been said it will be a Voltmeter, Ammeters went out with dynamo's if I recall correctly, think sixties.
Never forget however that it is a Morgan and many owners like adding modifications including to electrics.
A simple definition of the Ammeter is that it has to be in series with the battery whereas the Voltmeter is in parallel with the battery and that can be easily traced. Your reading of 14 does sound very much like the charging voltage to me this is a little high but these instruments are fairly agricultural tbh.

Here is a diagram with Voltmeter courtesy of Lorne.
Posted By: Image

Re: Voltmètre or Ampmeter? - 30/12/19 11:10 PM

My '75 has an alternator and an ammeter in the 'multi' instrument big dial.... As you say, ammeters are more of a dynamo thing so that is probably a transition thing.... With the voltmeter taking over by the time Toucan's '81 came along.... You can't rush these thing you know! :-)
K
Posted By: +8Rich

Re: Voltmètre or Ampmeter? - 30/12/19 11:12 PM

You are right it is a Morgan after all.
I guess as you say yours is a transition set up.
Posted By: John V6

Re: Voltmètre or Ampmeter? - 30/12/19 11:21 PM

The Gomog website will have wiring diagrams
Posted By: Image

Re: Voltmètre or Ampmeter? - 30/12/19 11:29 PM

The 'transition' was probably as long as it took them to run out of the big box of dynamo 'multi dials' they had out back. :-)

K
Posted By: +8Rich

Re: Voltmètre or Ampmeter? - 30/12/19 11:33 PM

laugh2 thumbs
Posted By: Taffmog

Re: Voltmètre or Ampmeter? - 31/12/19 01:35 AM

Ammeters were still use with alternators. +/- 30 for dynamos and +/- 50 for alternators.
Posted By: RichardV6

Re: Voltmètre or Ampmeter? - 31/12/19 09:02 AM

As already mentioned ammeters, which measure the current both going into and out of the battery (hence centre zero scale) generally went out of use when higher current alternators took over around the late 1960's. If you know what to look for they offer more immediate information on your cars electrical performance than a voltmeter. Downside is that all the battery current has to pass through the instrument or its shunt which is usually integral to it. This is an extra link in the chain involving higher current handling cables so generally not practical with modern car alternators putting out 50 + amps for reasons of reliability and cost. Higher current ammeters with remote shunts are available, the ones on my boat measuring up to 500 amps, but not practical for use on cars.

A voltmeter on the other hand is very easily fitted without interrupting any of the existing car electrics, allowing an approximate guide to battery state of charge before engine started and also if it is being charged to some degree afterwards.
Posted By: MDS61

Re: Voltmètre or Ampmeter? - 31/12/19 11:08 AM

I love instruments within the car to tell me "stuff".

However, as soon as one of these does something - out of the ordinary, I can go into a blind panic!

The missus modern however, does not even have a temp gauge, yet I never worry about the car over-heating....."knowing stuff - is important - but can worry you?"
Posted By: Toucan

Re: Voltmètre or Ampmeter? - 31/12/19 11:17 AM

JohnV6, l didn't find the one with Voltmeter,alll found were with Ammeter, including the one within the instructions booklet provided with the car and hopefully gone to me. Could you provide a link or send me the right one via MP?

BTW, thanks all of you who answered, it helps. I didn't know the link between Ammeter and dynamos / Voltmeter and alternator.
Seems that factory improvement was not synchronized with documentation update.
Posted By: +8Rich

Re: Voltmètre or Ampmeter? - 31/12/19 11:26 AM

If you click on the Blue Voltmeter link on my earlier reply you will see the link to the diagram from gomog they call it a volt gauge , Lorne is the owner of that very useful site. The diagram is for an 1988 model but the first one with a voltmeter I could find.
Posted By: John V6

Re: Voltmètre or Ampmeter? - 31/12/19 12:38 PM

Originally Posted by Toucan
JohnV6, l didn't find the one with Voltmeter,alll found were with Ammeter, including the one within the instructions booklet provided with the car and hopefully gone to me. Could you provide a link or send me the right one via MP?

BTW, thanks all of you who answered, it helps. I didn't know the link between Ammeter and dynamos / Voltmeter and alternator.
Seems that factory improvement was not synchronized with documentation update.

GoMog has an 84 car
http://www.gomog.com/allmorgan/Wiring44Diagram1984.jpg
and a 74 car
http://www.gomog.com/allmorgan/wiring44diagram1973.jpg

Both as you say show ammeters
Posted By: Image

Re: Voltmètre or Ampmeter? - 31/12/19 01:14 PM

I guess it took Morgan longer to use up their stock of wiring diagrams than it did their box of ammeters!! :-)

K
Posted By: Toucan

Re: Voltmètre or Ampmeter? - 31/12/19 02:26 PM

rofl
Posted By: Button

Re: Voltmètre or Ampmeter? - 31/12/19 09:33 PM

Originally Posted by MDS61
I love instruments within the car to tell me "stuff".

However, as soon as one of these does something - out of the ordinary, I can go into a blind panic!

The missus modern however, does not even have a temp gauge, yet I never worry about the car over-heating....."knowing stuff - is important - but can worry you?"


+1 - My '63 +4 has a ammeter as well as a voltmeter. Not sure what the ammeter does except scare the hell out of Me. As I have an Alternator I pay attention to the Voltmeter and not the ammeter. My Son In Law (auto electric mechanic) says the ammeter is "TROUBLE". Remove it!!!!!!
Posted By: RichardV6

Re: Voltmètre or Ampmeter? - 02/01/20 08:15 AM

Originally Posted by Button
My '63 +4 has a ammeter as well as a voltmeter. Not sure what the ammeter does except scare the hell out of Me. As I have an Alternator I pay attention to the Voltmeter and not the ammeter. My Son In Law (auto electric mechanic) says the ammeter is "TROUBLE". Remove it!!!!!!


Having both gives you the fullest picture on battery charging and electrical consumption but OTT on a car. Basically ammeter gives instantaneous info whilst voltmeter gives trend (cause and effect). Your SIL is right though in suggesting you remove ammeter unless it's kept for originality. The shunt within is necessarily a very low resistance so mechanically robust, but the extra cabling and connection's on what is the main power feed to all but starter add a degree of unecessary unreliability.
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