In time we will update our 1960 MK2 with 3.8L 4speed-OD from the original generator to a Delco 10SI internally regulated alternator. The update is fairly simple with having the internally regulated 10SI except what do do with the amp meter wiring

My question is what to do with the wires that feed the amp meter. I plan on installing a voltmeter instead. It looks like the wires can be disconnected on both ends and retired in place. Or do we still need to use on of them as a 12V feed to the center cluster. I recently did the same upgrade on an Austin Healey 3000, but there was not the complication of all the current going to an amp meter, as there was none.

Sorry for my initial confusion as we are just now looking at totally upgrading all the wiring with a new harness. See my recent post on a new main harness,

So for those of you who have changed to an alternator, how did you address the amp meter. I have read it is not advisable to keep it dues to the increased capacity of the alternator.

Thanks
jjsandsms

 

JJ when I converted my 1968 S Type from Pos to Neg earth all I had to do was reverse the wires on the Amp meter and left it in place. Without reversing the wires my Amp meter was showing a reverse of what it was actually doing ie discharging rather than charging, By reversing the wires the Amp meter is now working exactly as it should.

 

The ammeter measures and carries current to the ignition switch (and all the ignition switch controlled devices) and to the non- ignition controlled (the lights and some accessories). Most likely it will not be carrying current from the alternator to the battery, but that depends on how the alternator is installed. You could leave the ammeter connected - possibly with a bigger shunt (halved resistance) if it were carrying alternator current. If you take the ammeter out, because you want to put a voltmeter in its place on the instrument panel, you could simply connect the two cables that go to the back of the ammeter (and carefully cover the connection with insulation). I doubt that it's necessary to, or worth the effort of, adding new cables.

If you were to add some heavy current device like electric power steering, it would be wise to use a direct line to the battery through an ignition switch controlled relay (sort of similar to how the starter is wired and operated by the solenoid)
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i would consider at least two projects. one to replace the distributor with an alternator and two, to add a voltage gauge. a third may address the removal of the wiring for the ammeter, assuming you want it removed.

 

Sorry, re-reading it, my answer was over complicated. For the simple question of what to do with the two leads to the ammeter: connect them together.

 

Thanks for the replies thus far,

Yes I am going to replace the amp meter with a volt meter as part of the alternator upgrade. Looks like connecting the 2 amp meter wires is the simplest thing to do.

With regard to the volt meter, where would be the best spot in the center cluster to pick up the 12v feed for the volt meter?

By the way car is already converted to negative ground.

As far as other upgrades, A/C will be added but no other high draw additions such as electric power steering in in the mix.

Thanks
jjsandsms

 

It has been a while since I did the conversion, but I connected the amp meter leads together and insulated them. For the voltemter, I used a lead off one of the switched ignition wires, and used a spade connector off one of the fuseblocks.

 

In view of the proximity of the ignition switch, a short wire from the switched side to the voltmeter should be easy. The reading from a voltmeter requires more careful interpretation than an ammeter. If the voltage is a little low, it's clear something is taking a lot of current or the system isn't charging. The only alternator failure that I've experienced (and I think the most common) was in the regulator. The alternator was overcharging the battery, boiling the electrolyte. Detecting this at the voltmeter isn't easy. The battery is such a good sink of charge that the voltmeter will be only a shade higher than normal.

 

Stop fussing over the ammeter. I have done this alternator conversion a number of times on MK1s and MK2s and have had no problems with the original system.
I query the need for a voltmeter. Unless you know what a voltmeter is indicating the majority of people don't have a clue.
I understand this is a MK1 you are resurrecting and please preserve the basic instrumentation and woodwork as these cars are very rare.

 

Apologies. I made a mistake over the car, it being a MK2 rather than a MK1.
However, my remarks on keeping it original still apply.

 

There appears to be a general misunderstanding of the role of the ammeter in these cars.
It is simply a device to tell you that the battery is being charged or discharged.
It does not matter whether you have a 20-amp generator or a 100-amp alternator.
Either of these devices will be regulated to around 14 volts DC.
In operation the battery hangs across the electrical system and gets charged if the engine is running or discharged if the engine is not running.
If you want a voltmeter there are numbers of small digital devices which could sit on the parcel shelf.

 

As always, Bill has made a very good point: an ammeter is original and provides useful information. Why did manufacturers replace them with voltmeters roughly when they moved from dynamos to alternators? I'm going to suggest a couple of reasons neither of which relate to being useful to the driver.

First, apart from nicely decorating their dashboard, owners like to see needles on engine condition gauges sit steadily at the middle of the range. With an alternator, once the engine starts, an ammeter will momentarily make a big swing to hit the stop on the charge side.

Second, manufacturers want to avoid running heavy electric cable from the engine compartment to an ammeter on the dashboard and back again. It's cheaper and easier not to do it.

Some might claim that alternators are so reliable that they don't require monitoring and a voltmeter tells you more about the battery, but really how many drivers have such a sensitive eye? Modern cars have computers that control charging and condition of the battery and should inform you if everything isn't tip top. In fact, the alternator is giving up when the radio starts to moan and a tired battery shows up in something obscure like how hard you have to press the brake pedal for the starter button to work.
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Apologies if that seems a cynical view of manufacturers and owners.

 

As part of the conversion I did purchase a voltmeter (wasn't cheap) which generally look the same as the amp meter now in the car.

Here is a photo of the current amp meter and the new voltmeter. The new voltmeter does match the other gauges in appearance.

I do agree having all the current swimming around the dash can be a bit scary especially with the old deteriorating wiring.

Thanks
jjsandsms

 

Probably not much use in the US, but Reliant used the same pattern Smiths and Lucas instruments as Jaguar. Old ones (without the Jaguar association) sell at relatively modest prices on eBay.

 

all that's really needed and much more useful IMO is an idiot light. for the mechanism used for charging the battery and supplying electricity is either working or it's not. there's no advantage to having to look at a dial on a dashboard constantly to make that determination. it's a waste of time, a distraction, and probably a safety concern.