Alternator fusible link - Melted

[swokrams]

I was checking out the wiring on my A-4 trying to find out why the fuel, gas tank, and oil pressure gauges aren’t working. I discovered a blown fusible link on the back of the alternator housing. I think it ran from BAT to #2 regulator input but I’m not sure. It looks like the alternator may have been installed with a three wire circuit. There is an ammeter which appears to work and the system charges at least one battery in the usual way (high and then lower current).

I believe the alternator was purchased from MMI – mostly because the engine has just about every other MMI kit installed. It looks like the high output model with the cadmium(?) finish on the back cover. It is shiny and sort of orange. It is brand new.

Before I attempt to fix this, I’d like to know which alternator I have. Can anyone tell me how to identify the alternator and if the one I have sounds like the high ampacity unit sold by MMI?

If it is, can someone tell me what the fusible strap protects? I’d like to know before I replace it.

Thanks, Steve M.

[Don Moyer]

Steve,I'm having a bit of a problem identifying your alternator from your description. Could you send a picture?

Don

[swokrams]

Hi Don. It looks like the one you sell in your catalog. I will try to get a picture of the back where the conductive strap is located.

[swokrams]

Hi Don,

I was at the boat today (12/31) and took another look at the alternator. I didn't have a chance to look too closely - it was a quick visit. But the previous picture I showed you is not what my generator looks like. (Brain fart).

It looks like this snipet taken from one of the pin up photos in your gallery.

There is a thick grey wire in this picture which on my alternator is a metal stap (with a melted gap in the middle).

[Don Moyer]

Swokrams,

Your alternator is indeed one of our 55 amp API alternators. I'll forward your picture and comments to the manufacturer for a determination of what purpose the small rectangular electrical device serves. Before taking that step however, could you tell me why you believe the device is "blown"? I can't quite tell from the picture.

Meanwhile, the "B" terminal under the connecting lead of the device is the main (and only) output connection. This terminal should be the only connection to the battery bus, in your case through the ammeter. The fact that your alternator appears to be working OK (begins charging on the high side at startup and then dropping down) suggests that the device in question may be a noise suppressor of some type and not causing any negative effect in basic performance of the alternator.

Regards,

Don

[swokrams]

Hi Don,

I was out at the boat today and looked at the alternator again. It is indeed an API.

To be clear, the picture I attached in the previous email looks like the alternator I have, but is not exactly like my alternator. My alternator has a metal "strap" leading from the alternator output to the regulator input. The alternator in the picture shows a round "wire" connecting the alternator output to the regulator. My alternator uses a flat metal strap.

This issue has nothing to do with the small box which is also connected to the alternator output. (what is that thing anyway? a cap?).

Yes, the alternator output leads to the ammeter (orange wire) which is the connected to the battery via a red wire.

On my alternator, there is a red wire leading from the bottom alternator terminal to the + side of the ignition coil. This might be an error - was mayve supposed to be part of an idiot circuit to pick up the B+ voltage.

Here is my speculation. . .

There may be an error in the alternator wiring on my boat. Alternators can be wired with an idiot light where the battery + and the alternator + are compared. When one or the other is lower than the other, the idiot light turns on.

If I understand you correctly, you are saying there needs to be only one wire from the alternator, period. The regulator would control the current output (assuming the strap isn’t blown).

I am suspecting that my A-4 alternator is wiring somewhere inbetween a single wire and a three wire circuit. This would be consistent (with all due respect to the previous owner) with several other semi/partially installed upgrades I have had to correct or finish.

Sorry for the long dialog, but can you recommended a configuration for this alterntor (single wire or three wire).

Can you identify what the amperage rating of the fusible link might be? I need to replace it. I suspect my alternator rotor always runs at full current.

Or alternatively, should I just pull the alternator, take it to a shop and say, “fix it”?

Thanks for any light you migth be able to shed on the proper wiring of the API alternator.

Steve Markowski

[baileyem]

Steve
The 'fusible link' looks like a 'ZAP Stop'. A 'fuse' that is in the circuitry to stop the alternator from frying if someone turns the main elelectrical switch off while there is a load on the alternator. I assume that someone did turn your main switch off, the link did its job, and the alternator is still operating. I would replace the link before it happens again.

Mike

[swokrams]

I don't think so. The picture isn't my alternator, just one that looks like it. The gray wire in this pic is different than my alternator which has a bare metal strap instead of the insulated wire. I've got to pick up a digital camera and take a pic of mine and post it. Stay tuned.

In the meantime, here is a typical schematic of an alternator with an integrated regulator. I think the strap is probably an internal alternator-to-regulator connection - such as from the diode trio to the regulator? Just a guess.

Thanks for the suggestion though. :) I didn't know such protective devices existed. I think I'll pick one up!

Steve

[swokrams]

Food for thought - lots of head scratching.

[swokrams]

A picture is worth a thousand words. Here is the siruation. - Steve

[Jesse Delanoy]

I'm no expert, but it appears that the short gray wire, in the photo from the catalog, has been replaced with a bare metal link on your alternator. Also, it's hard to tell from the photo, but it looks like the metal link may be, or have been, in contact with the alternator case. If so, is it possible that the link grounded out to the case, caused a short, and melted the link (possibly doing additional damage to the alternator or regulator as well)? If the link is indeed a fuse, perhaps no damage was done, and it just needs replacing.

[swokrams]

Ah... good point. I think this explains it. If you look at the new alternator picture, you will see that the grey wire is actually a metal strip with a black insulating cover. Also, there are chared, melted platic lumps on the blown link indicating tht is once was insulated before it burned.

ALSO, if you look closely, there is another link like this on the lower part of the generator (just barely in view).

ALSO, the gray wire/link in the picture of the new alternator shows the original shape, before it got bent, shorted, and blew.

This also explains why the alternator could still work - the output from the stator is still connected to the battery. I expect it is not regulating properly as the link to the regulator input is blown.

Thanks a bunch. I'm headed to a TRACK Auto to get it tested.

Steve

[swokrams]

Don,

Thanks for taking my call today.

I called API and spoke with Brian. The blown link runs to the regulator sensor input. This connection carries a low current. I described the results of the alternator test I had done and he said the alternator is working correctly. It runs unregulated with the blown link. It regulates the voltage lower with the link connected.

Per Brian's directions, I can replace strap with a wire jumper. We probably will never know why the strap melted.

Steve

[jhwelch]

It looks like the red output wire from the alternator has some damage. Did
it come into contact with a hot soldering iron or was something
rubbing on it to wear the insulation away? It also looks like the
main feed from the battery is getting a bit rusty -- a wire brush
could touch that up.

-jonathan

[swokrams]

I don't know. I got the boat a few months ago and have just started digging into the engine compartment. The engine needs to be painted, the oil pressure gauge is intermittant, the head needs to be flushed, the thermostat is currently soaking in vinegar (it was clogged up), the fule gauge isn't working, I unjammed the choke cable, I relocated the dip stick extender kit (it didn't fit over the alternator), let's see what else... , oh yeah, the throttle control on the wheel tends to vibrate up in rpm, several wires have burned/melted protectors on them, it needs a PCV kit to help eliminate the smell, it has a gas leak somewhere which seems to be just big enough to smell, the oik change kit was instatalled with the wrong size hose for the pump, a fule/water separater is on-board, but still in a box, and the hose from the "T" tap for anti-freeze doesn't fit into anti-freeze jugs.

Fortunately, I love fixing these things. - Steve

[Don Moyer]

Good for you Steve. I'm glad to hear there is no apparent damage to the alternator internally. This 55 amp API alternator is essentially the very same piece of equipment we sold through API for approximately 10 years as a replacement for the original 35 amp Motorola. The alternator was originally marketed under the name of "Mando", and to my knowledge we have never had a single reported failure. Because of this good service record within the Atomic 4 fleet, when Mando went out of business several years ago, API began importing the separate components directly from the various manufacturers and assembling the alternators in their plant here in the US.

Don