Mystery device on Volvo 2001

[the_branflake]

Hello,

Could someone help in identifying or offering any info on what this device could be that is connected to the back of my alternator?

I have a VP2001 1991 with a saildrive attached. I also know that the engine has that negative isolator that you can see in the photo.

The device is connected via a fuse to the positive out terminal on the alternator and has another connection to that negative isolator.

Couple more pics here http://s1159.photobucket.com/albums/p628/the_branflake/

I also have a couple of earths going from the negative isolator to the block, is that correct??

Just in the process of getting all this sorted. Ive not had the boat long, but what i can say is that the engine starts, runs, charges, Tacho works, warning lights all operate as they should and ive not noticed anything wrong. Although i've not done any testing to see if this isolator is working properly.

I hope thats enough info.

As always many thanks for any info
Mat

 

[starfire]

It looks like a fairly big electrolytic capacitor, though why it there & what it is doing, I have no idea.

Others more familiar with the VP2001 may be along with a clue.

edit. It looks like the negative isolator has been linked out with those green/yellow wires.

I would be very tempted to pull that engine out & give it a little TLC, unless you have good access to sort things in place, while the saildrive looks clean, the engine looks like it has suffered a few leaks.

The electrics look like they are on their last legs.

 

[SimonD]

Suppressor (to prevent radio interference)?

 

[starfire]

Suppressor (to prevent radio interference)?

I don't think so, normally a suppressor would be a small, say 1uF non polarized cap.

But it was put there for a reason, judging by the (cleaner than the rest) crimps, recently, is it possible to ask the previous owner, who may have put it there ?

 

[Easticks28]

It looks like a fairly big electrolytic capacitor, though why it there & what it is doing, I have no idea.

Why would there be a fuse in the +ve to a capacitor?

 

[the_branflake]

I would be very tempted to pull that engine out & give it a little TLC, unless you have good access to sort things in place, while the saildrive looks clean, the engine looks like it has suffered a few leaks.

The electrics look like they are on their last legs.

Hi, Yeah i have fairly good access and have just finished working on the saildrive. The engine is my next target!!

The last owner wasn't sure either.

I think i need to check if that isolator is working this weekend. Also i did find some paper work for an inverter, could it be anything to do with this? The inverter was removed before i got the boat.

Thanks for replies so far.

 

[the_branflake]

Update

It does appear to be a capacitor. On close inspection i can just make out something like 150 or 1500uf and a small RS stamp on the top.

So what could its purpose be?

What might i notice if its removed?

 

[VicS]

It does appear to be a capacitor. On close inspection i can just make out something like 150 or 1500uf and a small RS stamp on the top.

So what could its purpose be?

What might i notice if its removed?

I can only assume it was added to overcome some radio interference problem. It may or may not have been effective.

Id take it off.

 

[William_H]

Capacitor on alternator output

Yes I agree it is probably an electrolytic capacitor fitted in an attempt to reduce radio interference from the alternator. Alternators don't usually cause a lot of radio interference. Usually a smaller value capacitor is sufficient. In this installation the long leads tend to provide inductance which stops the high frequencies being bypassed. The preferred style being a feed through capacitor which is cylindrical with a stud at each end. The body is earthed and the generator output goes to one end and out the other. The stud is just a continuous bolt. Or better still is a filter which has an inductance (choke) in line with the alternator output and appropriate small and large bypass capacitors on the input.

Often however a badly interfering alternator has a diode dead so it will not charge full current (often not noticed) but means the output is syncopated with each AC cycle so makes interference.

The fuse on the capacitor is because large electrolytic capacitors often have a failure mode going short circuit hence the good idea of fitting a fuse.
OP can easily remove the fuse to see if it makes any difference. Check the fuse for condition (and the holder) as these fuse holders are not very reliable anyway. It may have disconnected itself long ago.
good luck olewill

 

[nigelmercier]

What terminal does it go to?

 

[the_branflake]

Hello,

It was wired to the alternator + output terminal and battery negative.