TR6 Ammeter blown.. bypass?

[Doug Sabbag]

Hi guys,
I have a 1969 Triumph TR6.

I have been installing a new front wiring harness and while doing that, at one point I hooked up the battery to wire up the ammeter to start the car and I had the brown & white wire on the connector which the solid brown wire was on.
Sparks flew and the alternator was blown.

After I installed a new alternator, I'm seeing no movement of the ammeter needle and reading just under 12 volts on the battery.
So, the alternator isn't charging the battery.
So, apparently I blew out the ammeter too, and without that, the alternator output isn't getting to the battery.

So... I'm wondering if I can temporarily bypass the ammeter so the alternator will charge the battery?
I'm afraid to run a wire connecting both ammeter terminals, because I don't want to blow another alternator.
Is there anything I can do until I get a new ammeter?

Help sure will be appreciated!
Thank you,
Doug

 

[mctriumph]

Have the new alt checked first ,I do not think the amp meter fails in this way. But it is an easy fix.
if it has. A good up grade on a 6 is to add a fuse to the brown lead (know to leak smoke).
Mad dog

 

[Doug Sabbag]

Have the new alt checked first ,I do not think the amp meter fails in this way. But it is an easy fix.
if it has. A good up grade on a 6 is to add a fuse to the brown lead (know to leak smoke).
Mad dog

I did have to 'adapt' the new alternator to the 1969 wiring, i.e., couldn't just attach the 2 plugs I had, into the new alternator.
So I followed some schematic which gets you down to just 2 wires instead of 5 and no more ground.

 

[Doug Sabbag]

Have the new alt checked first ,I do not think the amp meter fails in this way. But it is an easy fix.
if it has. A good up grade on a 6 is to add a fuse to the brown lead (know to leak smoke).
Mad dog

Also, does it matter which side of the amp meter the NW wires are attached to?

 

[Sarastro]

I can't see why connecting the brown-white wire to the wrong terminal of the ammeter would cause a problem, other than no indication from the ammeter. The brown wire is from the battery to the ammeter and the BW goes to the alternator, light switch and ignition switch. I can't see why that would result in visual sparks and it certainly wouldn't kill the ammeter. It sounds to me like there are wiring errors elsewhere. Or, maybe the alternator was blown before you started.

But to answer your question, there is no harm in putting a jumper across the ammeter. But I also doubt that your ammeter is blown. You can check it with a multimeter--if it's blown, there will be no conduction between the terminals.

 

[CJD]

You can bypass the ammeter by just jumping the 2 large connectors. Before doing that, however, I would check for continuity (ohms) between the connectors on the back of the ammeter. They should read less than 1 ohm if the ammeter is good. But!...

I would assume the fuse would blow long before you overloaded the ammeter enough to kill it. If the ammeter blew, that would infer that you have a major wiring issue. Any time I check a large wiring rebuild, I do not directly hook up the battery, but rather run one lead of the battery through a 12v test light. That way, even with a direct short in your harness, the worst it will do is light up the test light. With all switches off, the light should also be off. Then, test switches one at a time, while watching the light. With each switch it should come on dim, along with whatever system the switch powers. If it comes on very bright...then you have a short past that switch (or a very heavy load, like the starter motor.)

The test light saves the step envolving the sparks and smoke!!

 

[Doug Sabbag]

You can bypass the ammeter by just jumping the 2 large connectors. Before doing that, however, I would check for continuity (ohms) between the connectors on the back of the ammeter. They should read less than 1 ohm if the ammeter is good. But!...

I would assume the fuse would blow long before you overloaded the ammeter enough to kill it. If the ammeter blew, that would infer that you have a major wiring issue. Any time I check a large wiring rebuild, I do not directly hook up the battery, but rather run one lead of the battery through a 12v test light. That way, even with a direct short in your harness, the worst it will do is light up the test light. With all switches off, the light should also be off. Then, test switches one at a time, while watching the light. With each switch it should come on dim, along with whatever system the switch powers. If it comes on very bright...then you have a short past that switch (or a very heavy load, like the starter motor.)

The test light saves the step envolving the sparks and smoke!!

What 'fuse' are you referring to?
I only have fuses in the fuse box.
are you talking about one of those?

I'm thinking the alternator I received which only provides 2 output / connections, isn't working with my 1969 wiring.
Though they provided a schematic for adapting my older wiring to this newer alternator, that schematic doesn't take into account how many wires I HAVE to connect.
I must connect an NW, NY and NR.
This new alternator is only set up for NW and NY.
I need the NR too.
Looking at my schematic, it seems clear that my ignition switch and the direct battery wire to the starter should work, no matter what is going on with the ammeter. So, just because she starts, isn't telling me the ammeter is good.

So, I'm thinking I really need to reinstall my old alternator, plug the plugs in and possibly bypass the ammeter.
I opened up the alternator and nothing 'looks' fried, of course if diodes are gone, I couldn't tell by looking.
I see my style of alternators at Roadster Factory, so if this alternator really is fried, I'll bite the bullet and buy that.
We'll see.

 

[Sarastro]

Before you panic and keep buying things, let's figure out what is going on.

First, any alternator needs two wires: the heavy output wire (the NW) and something to operate the ignition idiot light (NY, in the diagram I posted). The NR, I suspect, is a sense wire, which not all alternators have. If your new one doesn't have it, just tape the connector and let it dangle. I don't know what the NY jumper on the original is for, but if your new alternator doesn't have the two terminals, you don't need them both. Just connect the NY wire from the idiot light to whatever terminal is provided.

So, we're down to two wires, two terminals.

I take it that, if you disconnect the alternator, all the electrics work normally. In that case you should get a small current, maybe 5-10 amps, when you turn on the ignition switch. It should increase when you turn on other electrical equipment, like headlights, turn signals and so on. If you see that, the ammeter is fine.

If the electrics work but the ammeter doesn't indicate, there is something wrong with the mechanism internally. The ammeter is really simple; it consists of a loop of heavy wire and a pointer mechanism. The pointer moves in response to the magnetic field around the wire. So, even if the ammeter doesn't indicate, it still is usually possible for it to carry current normally. It's pretty hard to blow out that loop in the ammeter, but I suppose that, with enough current, it's possible. But if you blow it, it turns off almost everything in the car, so you can't do that without realizing it.

I would do this:

1. Make sure the electrics are working normally with the alternator disconnected.
2. Make sure you are getting reasonable readings on the ammeter, as I described above.
3. Hook up the alternator, start the car, and see if you observe charge current on the ammeter.

If you see charge current, the alternator is OK. If not, it's either bad or you haven't connected it correctly.

 

[Doug Sabbag]

Hi Sarastro,
Well, the ammeter needle is positioned slightly to the right - discharge - with zero movement, whether the car is running, or any lights, etc., are on or off.

Thinking my alternator was blown, I purchased a 60 amp one, without knowing it wasn't going to mate with my existing (2) plugs, which connect 1 heavy NW, 3 thin NYs and 1 thin N.

According to my schematic, that thin N goes, along with another N from the fuse box, to a 'block' which feeds another N, to the starter, which is connected at the starter with the wire from the battery.
The other side of that N, at the fuse box, are 2 Purple wires, which feed power to the horns, which are working.

All of that tells me that thin N coming from that block, is feeding power from the battery, to the alternator.
And, this new alternator doesn't need that.
Ok.

So, back to what this alternator DOES need, or expect, is 1 NY.
I have 1 NY and a double of 2 NYs, so I have 3 NYs.

Understanding that 2 NYs just connect 1 terminal to the other one, in the original alternator, leaves 1 NY as useful to the new alternator.

So, I assumed the single NY was that one and initially connected that to the new alternator with the thick NW to the positive connector.
That did nothing.
The car starts and runs fine, the lights work, the wipers, the horn, but the voltage at the battery is just slightly under 12v and, of course, the ammeter doesn't even flinch.

So, I tried the pair of NYs, which did nothing. Then I tried all 3 NYs, which did nothing. Then, I tried the thin N, alone, then with 1 NY, then all 3 NYs and the N.
None of any of those connections does anything, i.e., the voltage at the battery remains just shy of 12 and the ammeter does not budge at all.

So.... I'm stuck with a new $250 alternator, which does nothing.

Tomorrow I will try my original one, which the 2 original plugs will happily connect to. I might well still have no change, but, there I am.

Next, I can buy an original configuration alternator and see what that does.
Otherwise, I can drive until this battery is dead.

Any other advice?

 

[Sarastro]

Well, if the ammeter needle is not moving, there's something wrong with it, so you can't draw any conclusions from what it does.

If you leave off the NY wires from the alternator, it shouldn't affect the alternator's operation, just the ignition lamp. So you can leave those off for now, as they are just confusing things.

I'm more concerned by the fact that the system voltage doesn't increase with the alternator connected and the engine running. If it's wired right, you should see the system voltage rise to about 14V when it is charging properly. So, it sounds like the alternator may have gone to that great electrical system in the sky.

The only things I would check at this point--make sure you're seeing battery voltage at the alternator's output (heavy NW) with everything off, and you could try a jumper across the ammeter just to be sure it's not the problem. But unless there is some unrecognized

 

[Sarastro]

By the way, these meters are often not perfectly zeroed (mine isn't), so if the pointer is a little one side of zero, and it stays there when all the power is turned off, you can take that as zero.