voltmeter

[nigel]

Can anyone tell me if this is normal.
when the car is running the voltmeter reads three quarters and I have a 14v reading from the alternator at the battery (which is brand new).
but if i turn on the lights heater and wipers the reading drops to one quarter.
I dont think this is correct if its not any ideas?

[UKPhilTR7]

Is this when idle or running? I know that mine goes down to about half when I have the electric fan on , but dropping down that much with the things on does not sound too good at all.

[nigel]

This happens even when I am driving. I would expect it to drop to half as yours does

[Cobber]

You need to do a load test of the charging system.
This is done with a load tester to see what voltage your getting with an artificial load applied.
But you probably don't have such an instrument, so you can turn everything on, such as high beam, heater fan, wipers and hazards etc.
and with some revs, take a voltage reading using a multimeter, not the rubbish gauge Triumph stuck in the dash.
One must remember the gauges in the dash are to be used as an indicator, they're not to be taken as gospel.

"Keep calm, relax, focus on the problem & PULL THE BLOODY TRIGGER"

80'Triumph TR7, 73'Land Rover (Ford 351. V8),
'89 Ford Fairlane
'98 MG-F, 69'Ford F250.

[Hasbeen]

I found that a standard alternator, even after being overhauled & in very good condition, could not maintain battery voltage if the lights, wipers & the radio were running, let alone the ventilation fan. If an electric radiator fan was added, you could cool the engine, or use the lights, or the wipers, but not all of them.

Even without the lights, it could not run the rest.

There are a number of people offering an 85 amp output alternator kit. This is really only just enough to maintain my voltage, on a hot wet night, after I installed, & used the air conditioning.

Hasbeen

PS. That alternator, [with 25 or 35 amps output what ever it is] fully overhauled & used for just a few days, is in the shed, available free to anyone who can find a use for it. It might run a day time only track car.

H

[FI Spyder]

Mine reads 14.5 volts with battery fully charged (the reading will go up as the battery gets charged creating more resistance). With lights. heater, etc. going it drops down just a little on the voltmeter by indicated by lights only slightly dimmer, signals only slightly slower. On the voltmeter gauge it drops down a needle width or two max. Having A/C it must have the higher output alternator. I have taken apart the alternator initially and replaced the brushes (I think, the old ones weren't bad and I can't really remember if I changed them out while I had it apart) and I cleaned the oxide off the commutator. All wire connections (in the car)were cleaned while I had the dash and heater out and as I was going over the car (first winter project preparing it for out of country safety check). The battery has just been replaced after being in there for 8 years. This would be the optimum one can expect from the higher output factory alternater.

- - -TR7 Spider - - - 1978 Spitfire- - - - 1976 Spitfire - - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra - Yellow TCT

[nigel]

I have just done a test battery reads 12.76 volts,with the engine running volts reads 14.2v with lights heater and wipers on i have a reading 13.45 this sounds ok to me but the dashboard voltmeter reads a quarter.

[Cobber]

Then the gauge is probably stuffed

"Keep calm, relax, focus on the problem & PULL THE BLOODY TRIGGER"

80'Triumph TR7, 73'Land Rover (Ford 351. V8),
'89 Ford Fairlane
'98 MG-F, 69'Ford F250.

[qac]

I BOUGHT AN ELECTRIC METER FOR ALL A/C BUT IT NOT ONLY READS D/C VOLTS ITS ALSO A D/C AMPS . READ THE AMPS DRAW AT THE BATTERY WITH NO EXTRAS ,THAN ADD A FAN & READ, THAN ADD WIPPERS& READ AND SO ON . MATCH THE ALTERNATOR DESIGN LOAD AMPS AND YOU HAVE A BETTER I/d OF THE PROBLEM

QAC ACROSS THE POND

[sonscar]

Do not think of it as a voltmeter,think of it as an indicator,30 years old and with it's own charming ways.It has no calibrations so it's accuracy cannot be verified.Remember where it normally runs and if suddenly it is in a different place then investigate.Triumph put a red segment at the very top and bottom so I work on the principle if it is not in either of them things are(probably) ok.Steve..

[UKPhilTR7]

From what you have said it does seem like the volt meter has gone and needs to be replaced.

I do like the last comment about the top and bottom red sections and think that is a good rule to live by with our questionable volt meters. I have a new starter and Alternator on the way which I am hoping will help my overall car charging.

[Beans]

It's not a Volt meter, it indicates the amount with which the battery is charged.
The more power users you switch on means less charge.
Which in turn will drop the needle.

Might well be three's nothing wrong there.
And do bear in mind the original alternator isn't the most powerful.


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[FI Spyder]

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Beans</i>

It's not a Volt meter, it indicates the amount with which the battery is charged.
The more power users you switch on means less charge.
Which in turn will drop the needle.
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

This is true in one sense but as the voltage, resistance, current (amps) all tied in together it is measuring voltage in one sense or another but it's not really a voltmeter per se unlike the volt/ohm meter you would put across the battery terminals to measure battery voltage or alternator voltage if the car is running. More of a charging system gauge (you are gauging the system rather than measuring it) than any kind of meter.

- - -TR7 Spider - - - 1978 Spitfire- - - - 1976 Spitfire - - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra - Yellow TCT