what's this thing that's attached to my alternator?

[Cptkid570]

1985 Mercrusiser 260 (5.7 liter)

I’m going to try to post a picture of it to give you all some clarity. But, I’m trying to figure out what a particular part is on my engine. It’s a light blue canister looking thing. It has a red wire going to my alternator and a black wire going to the engine block.

Is this some sort of voltage regulator? If I change to a different alternator (I think the one I already have sitting around is a Mando) will I need it?

I looked at this link (http://www.ebasicpower.com/charge/alternatorwiring.htm) and it showed that an early Prestolite alternator had a voltage regulator & with a red wire and black wire, but also said it was for OMC’s. I bought the boat used, so who knows what the put in it. I’m just trying to figure out if I’ll need it for my new alternator. (and how to wire up my new alternator – which may be in another post)

 

[Cptkid570]

Re: what's this thing that's attached to my alternator?

 

[tommays]

Re: what's this thing that's attached to my alternator?

Its a capacitor AND IMHP it should not be there

Somebody did some shadetree wireing in the past

Tommays

 

[Cptkid570]

Re: what's this thing that's attached to my alternator?

 

[Cptkid570]

Re: what's this thing that's attached to my alternator?

What does it do?

 

[tommays]

Re: what's this thing that's attached to my alternator?

I would WAG it was some kinda of attempt to stop high voltage spikes from a bad chargeing system ?

Never saw one in a boat before so its hard to say


Tommays

 

[Cptkid570]

Re: what's this thing that's attached to my alternator?

If it has wires on it, and isn't built for a boat, it may not be a good thing to have it in there!

I'll be putting a different alternator in anyway, so I'll just throw out that capacitor with the old alternator.

Thank you very much for your help.

 

[Don S]

Re: what's this thing that's attached to my alternator?

Capacitors like that were needed on alternators to stop the electonic noise that killed LORAN reception.
In case you don't know, LORAN was the method of finding where you were before GPS.

 

[Cptkid570]

Re: what's this thing that's attached to my alternator?

hahaha - I think this boat still has a loran on it!

I'm glad that I'll be able to toss this capacitor.

I'm going to be swapping alternators soon. I haven't really had a chance to take a good look at the back of the old or the new alternator yet.. but, I'm sure I'll be posting on here for some help figuring out which wire goes where.

I'd just bought this new alternator for my other boat before the engine died on it..so, I hope to use it on my current boat.

 

[johnbo]

Re: what's this thing that's attached to my alternator?

That capacitor is most likely dead at this point. Electrolytic capacitors are quite picky about the voltage that's applied to them. Applying voltages much above the rated voltage seriously degrades them.

Your capacitor was rated for 15 WVDC (Working Volts DC). Because of the spikes present in automotive/marine charging systems, I would guess that a 100V rated would have been needed.

The value of 21000 uF (micro Farads) is pretty high and would have been used in a DC power supply. It was aimed at suppressing ripple in the DC. For spike suppression, this would not have been a good choice, a much lower, non-electrolytic cap would have been much more effective.

Still its a hack. Has no place there. That part was not meant for that application. The good news is that it hasn't blown up yet. That is one of the side effects of too high of voltage on an electrolytic cap. But, generally they just break down internally and stop being a capacitor.

Yank it.

johnbo

 

[Boatist]

Re: what's this thing that's attached to my alternator?

That Capacitor is clearly not made for boats. It is a homemade atemp to fix a noise problem.
A good Loran C filter would have a coil and capacitor.
The Capacitor should be rated at twice the voltage it is filtering so in this
application should be 25 volts or 50 volts.

Alternator noise filters used for CB Radios or Single sideband Marine radio and Loran C.

The one you have is clearly not made for a boat and is too Large to be an effective filter..

Since the voltage rating is 15 volts your lucky if it not shorted out loading the alternator.

I also still use a Loran C and did try a Loran C filter to try and eliminate power noise
created by a Floresence light. It had no effect and it was a Capacitor / Coil design.