To those using a Dinoparts Voltmeter as replacement for the Amperemeter

Hi Adrian,
I did not even know that Dinoparts offered such a device. What a remarkably dumb idea!

Every time I start up the Dino, I look at the instruments and say a quiet thank you to the engineers at Ferrari for having the wisdom of including a genuine, honest-to-goodness ammeter in the dashboard. It costs more to do so, and it requires more heavy copper wire to implement in a design. But only a real ammeter can tell you everything about the charging system and the battery. A voltmeter will tell you next to nothing. Even worse, it tells you what is supposed to happen - not what is actually happening in the system. Only a real ammeter can do that.

I hope you will remove that useless toy and re-install the real ammeter. I agree with you, there is nothing wrong with that. Sure, you could have problems if the wires are loose, but so what? I know a lot of wires that could cause problems in a Dino if they are loose or corroded. Better to make sure that all connections are clean and tight, instead of ruining a good and thoughtful design with poorly designed aftermarket devices. At least, that is how I feel about it.

Lars

 

I thought the voltmeter was the better gauge to have, it shows actual voltage in the system as opposed to current flow.

 

It may seem like it, but it is not. In the automotive charging system, everything is revolving around the current that is flowing into or out of the battery. The (charging) voltage is just the facilitator. For example, you may have a defective battery, which no longer accepts any charge. Everything would look fine on the voltmeter - at least while you are driving - but an ammeter would warn you by showing the abnormally low charging current.

Think about it this way: When you put a discharged battery on mains operated battery charger, that charger usually has an ammeter. The ammeter tells you everything: How deeply discharged the battery was (battery is soaking up maximum current from the charger), how healthy the battery is (by the number of hours that it keeps soaking up that heavy current) and when the battery is fully charged (current falls to near zero).
Now imagine if that charger had a voltmeter instead of an ammeter on its front panel. The voltmeter would show its 13.8 - 14.3 V all the time. That would not tell you anything, except that the charger is working.
Seeing how many amps are flowing into the battery, and for how many hours, is the only way to know that real Amperehours are being stored in the battery.

 

The allegation that the ammeter is the source of flames starting in the dash is well known from Corbani's cautioning posts but I've found the dust and dirt forming on the Bosch ignition contacts is more prone to this. Keep the Ammeter contacts solid and secure to prevent problems.

 

Yes i was warned some time ago by JC about this and when i did my dash i actually seperated the wires from the loom. About 600mm from the ammeter the wires showed signs of overheating!!

Thanks for the info, i am converted

 

Just to clarify: A voltmeter is a very nice and useful device to have in a vintage car. It is only when it is used to replace a real ammeter that it is a step backwards, in my opinion. As a complement to the ammeter, it is perfect.

Came to think of it, Adrian, the voltmeter from Dinoparts is probaly intentionally designed to exaggerate the deflections below and above normal values. It may be an attempt to get the attention of the driver in case of a failure. The actual voltage difference between a good system and a defective one is of course fairly small (initially at least), and may otherwise be missed by the driver. That way, the voltmeter also mimicks the movements of an ammeter. A valid concept, I suppose. I should not have called it a dumb idea, though. Sorry! That is too strong. I should have said that I personally don´t like the approach and that I would never remove the ammeter from my car.

A voltmeter in a car can never replace a real ammeter, but it is still a huge improvement over a system with only a generator/alternator warning light.
It is strange that just yesterday, I got to experience the shortcomings with such a system, and it nearly left me stranded:

I have an old unrestored original Giulietta Berlina TI, which has been mostly sitting for a long time. I thought it was time to get it registred and taken on the road. That required making an appointment to have the car inspected for registration (it was imported from another European country). So, yesterday, I fired up old Miss Giulietta and took her on the 45 minute drive to the inspection station. I drove with the headlights on all the time - as is required by law here. Of course, it was raining too! The inspection went well, but when it was time to start the trip back, the battery was almost completely dead. Without knowing it, I had been driving on mostly battery power! There had been no indication that anything was wrong. The "DINAMO" light had behaved normally, coming on only at idle.
Fortunately, I managed (just barely) to get it started and headed home, navigating nervously through the torrential downpour while the headlights were getting dimmer and dimmer.... Made it home, luckily, and put the voltmeter on the system: 9.0 V at idle, only 10.2V at higher rpms with lights on. No wonder. With headlights off, the voltage slowly moved up to almost normal levels.

Obviously, the generator is tired and in need of a rebuild. It tries to put out some voltage, but it is totally incapable of supplying the heavy current required by the headlights and wipers. The majority of that current is drawn from the battery instead.
An ammeter would have indicated the problem as soon as I turned the lights on. An accurate voltmeter would also have given me some warning, but not as immediately or as clearly as the ammeter (because the battery would keep the voltage up for a while). Still, it would have warned me.
The warning light gives no warning at all in a situation like this. It is very deceptive. Only if the fanbelt breakes, or the generator/alternator dies completely, does the warning light come on.

In the Giulietta, once the generator is rebuilt, and I have measured the currents with an external ammeter, I plan to keep a digital voltmeter in the glove compartment, and to monitor the voltages frequently - with the headlights turned on!

In the Dino, we are fortunate to have an ammeter. Keep an eye on it now and then! It provides some very useful information. A digital voltmeter in the glove compartment would not hurt, there either.

 

I had a similar problem last week with my 246. I drove home and stopped the car. When I got back in to start it, it was dead. I tried charging the battery, but it would not hold a charge. Thinking that my 6 year old battery was the problem, I purchased a new one. When installed , the car started, but the ammeter was below the half way mark. I checked the alternator fuse and belts--all working. My next thought was the Marelli voltage regulator.
Am I thinking correctly? Whats the best way to check the voltage regulator. If it is bad does anyone recommend the newer electronic regulators?

 

This may help you

http://www.ferrarichat.com/forum/showthread.php?t=237645&highlight=alternator

In addition to the problem i encountered i eventually found after numerous tests that the ammeter wire at the battery terminal was completely Sc&**d and after remaking the joint the high resistance was gone and everything worked great afterwards.

Sounds like your alternator has stopped working to me.

If the above link doesnt answer your question try searching "alternator" in the search field, most dino owners get this problem and there is plenty written on the subject

Tony

 

Here is the way I check my Voltage regulator
http://www.ferrarichat.com/forum/showthread.php?t=193757

Here is how I chose and installed an alt with solid state voltage regulator
http://www.ferrarichat.com/forum/showthread.php?t=268373