ammeter question

[Ray Morley]

1970 Kadett Rallye 1.9

Here is the scenario:

Engine off: turn on headlights and the ammeter shows a discharge......normal indication.

Engine on: ammeter reads just slightly above the 'O' mark BUT when you turn on any electrics the ammeter goes to full positive indication.


With the engine running I disconnect the negative battery cable and the engine runs smoother and the ammeter indication returns to normal.

When I re-connect the negative cable the ammeter indication reads normal again until I turn on an electric and then the scale goes full positive again.

Any ideas?

[BQS4]

Ray;
It may be a bad ground somewhere, and the "somewhere" is the bad part.

[timemachine]

Ray,

This could be a tricky one, but three possible candidates are a) high resistance in the charging system, b) a faulty voltage regulator or c) a faulty alternator. You should fix it or have it fixed to avoid the possibility of an electrical fire. That the symptom only occurs when a load is applied tells me it is probably not a faulty ammeter.

a) High resistance in the charging system can be caused by a deteriorating ignition switch contact. You can go around this by connecting a wire directly from the positive terminal of the battery to the positive side of the ignition coil. (Along with jumping the starter with a screwdriver blade, this is how you hotwire a car from under the hood. We didn't always have steering column locks.)

b, c) Understand that the ammeter is only telling you how much current the battery is asking for from the alternator. It does not measure the total output which is naturally higher than zero. So, with the engine running and the negative disconnected from the battery, the ammeter should read zero because there is no load on the circuit. By relation, if the battery is called on to provide power the alternator can't keep up overall it will show a discharge at some rate and eventually the idiot light turns on too. The ammeter will read +2-10 amps when a discharged but good battery is connected. (A dying battery may not ask for a charge by contrast).

If the battery is good and charged, another reason the ammeter will read high is because the source ac voltage is too high, or because the regulator is faulty or misadjusted. Because turning on another circuit causes this is explicable by the charging circuit turning on when the load is applied.

It's the regulator's job to balance the demand for power with the speed of the alternator's turning to deliver steady voltage which should be around 14.2 V DC when the car is running. (With the car and all circuits off the battery normally reads 10-12 volts.) Ammeter current is measured relative to voltage. With everything connected and the car running, place a voltmeter across the battery terminals. If it is higher than 15 volts or so you should adjust or better, replace the regulator.

It is possible that the car runs better with the battery disconnected because high voltage is causing distributor arcing. I don't know about Opels, but some alternators should not run disconnected from the battery for fear of rectifier damage due to no load.

Hope this helps.

Jim

[Ray Morley]

Thanks Jim:

I use a bypass (OttoStart) system and the ignition switch on the car is new so thats probably not the problem.

With the engine running and ammeter showing full positive deflection the battery (pole to pole) is around 12 volts.

When I disconnect the voltage regulator connector the ammeter shows normal indications but I am now seeing the red idiot light (dimmly).

This is a strange problem as yesterday everything was working fine.

[Ray Morley]

I think I solved the problem.

I did a minor adjustment on the spring tab in the Voltage Regulator and I now have the ammeter reading +5 at idle. I also cleaned the two sets of contactors (they looked like igntion points) as they were pitted and not making good contact with each other. The car seems to idle alot smoother too.

[timemachine]

Ray,

That's good, the dirty contacts would account for high resistance, but the ammeter should get back to zero once the battery is charged. Besides cleaning, you should be able to adjust the regulator with a screwdriver until voltage is about +13.8-14.3 DC.
Better to replace it though. If the regulator uses a T-connector on the bottom you can swap it with any 1.9L 12V Opel regulator or similar period piece of the time. There are some on ebay from time to time or just go to rockauto and find one that looks the same:
https://www.rockauto.com/dbphp/mak,OPEL,1971

Good luck,

Jim

[Ray Morley]

Thanks for the link.

The Voltage Regulator on my car has the 3 tangs for the connector but it also has another wire that is separate that attaches to a shunt on the car body. Does this wire control the 'idiot' light ?

[timemachine]

Ray,

I'm not sure what you mean by a "shunt on the car body." Does it go to ground, which might be a normal design thing, or into a harness or other connection? I don't know Kadette's very well but normally the ammeter and idiot light are wired in separate circuits directly from one of the wires on the three-prong attachment. Mantas and GTs use just the three-wire connector and are grounded by their physical attachment to the body. Post a pic or maybe somebody else with a Kadette could have a look.

Jim

[Ray Morley]

Hi Jim

The V.R. has the 3 wires on the connector that goes down to the Alternator.

As you can see in the pic a seperate BLUE/WHITE wire goes over to the shunt where it ties in to another wire that I think by the wiring diagram goes into the the dash and is the red low voltage light.

Ray

[timemachine]

How does the extra wire connect to the regulator? Is there a separate terminal or is it part of the three-prong connection? Looks like a standard Manta/Ascona/GT regulator from here.

Jim

[Ray Morley]

The extra wire is not a part of the 3 prong connector and it enters the bottom of the V.R. about 1" beside it.

[Ray Morley]

Sorry Jim.........I had a brain freeze.

The Blue/White wire IS a part of the 3 tab connector plug.

[timemachine]

Ray,

You're in business then, swap in any contemporary 1.9 L Opel regulator or buy one of the aftermarket ones at Rock Auto. I've used them before and they work fine.

Jim

[jvandyke]

If I can piggyback on this thread.
My GT's ammeter has always (for the last few months total ownership) Read near zero, as you'd expect. The other night I was messing with stuff electrical and left the key on. Oops. I hooked up a tender for a few hours. Ran car then and commuted to work today. Meter has been on first mark to positive ever since. I would think the battery would have been recharged by now (commute to work is 16 miles at 70mph) but meters is still reading one mark to the plus side. Which, if I understand stuff, means the system is sending the battery voltage all the time. Would this indicate that I have an issue to hunt and resolve? My first move will be to start checking voltages but maybe it just takes longer then I think to build the battery back up?

[namba209]

There's a whole bunch of things that can do what you've indicated. Condition of the battery, the connections, alternator condition, and last but not least, sticking points in the regulator if it's one of the older, non solid state. Checking the battery voltage with the engine off and again running is a good check, if nothing more than to give you peace of mind.

[timemachine]

I've seen a lot of Opel ammeters "zero" just above the midpoint. So check with the car off versus on to see what it's telling you. Ron laid out the usual culprits including the regulator which seems to have been Ray's problem, but a very slight positive charge is not something I'd worry too much about. Always good to check those connections once in a while though.

Jim

[Ray Morley]

I have gained alot of insight of Voltage Regulators from this thread.

The official OPEL tech manual states that the that the Voltage Regulator will provide the battery with a +5 Amp charging allowance.

It does not say that you will always be seeing +5 on your Ammeter.

After I had solved my problem I was seeing the +5 indication and after the engine had been running for awhile I turned it off. The next day when the car was started the Ammeter read 0 and as I turned on electrics I could see a draw on the guage.


My guess is........that when the battery needs to 'top up' its charge the V.R. allows a max of 5 Amps to do that and when its back to normal the Ammeter will go back to 0 again.

One way to check this theory would be to start the engine and observe a 0 indication. Turn the engine off and turn on your headlights and let them run off of the battery for a short time and then start the engine again. If this holds true then the battery should need a slight charge and the Ammeter should show +5.

[73Manta72gt]

I think the old ammeters get sticky and if you put them in a discharge condition and make the pointer swing off center...like leaving the lights on it frees up the movement or seems to. I first noticed this on a Manta after leaving the lights on for a few hours. Now the pointer always shows about 5A when driving where before it would just move slightly above zero like it was stuck.

[Ray Morley]

The BLUE/WHITE wire thingie has me confused.

On my V.R. this wire comes out of the connector at the V.R. and then connects to the shunt as I had shown in one of my posted photos.

Now if you look at the wiring diagram photo attached you can see that this BLUE/WHITE wire is at the Alternator side but still goes to the same shunt.

Does it matter which way the harness is connected? If I switched the harness around and used a longer BLUE/WHITE wire will it make any difference? I guess what I am trying to explain is:

The B/W wire has two possible attachments...........the V.R. and the Alternator. Which end should it be at?

[timemachine]

Ray,

Your note about the charge state of the battery is right. Go back to my first reply.

As for the wire, you'll note that the t-connector on the ammeter goes right to the t-connector on the alternator, so it doesn't matter electrically which end the blue/white wire is connected at as long as it's the right terminal. Since all was well before, I'd leave it be unless something is exposed or chafing.

Jim