Attn Volvopaul and spannerman

[DavidJ]

Reguarding you both as the fountains of all knowledge, I have an interesting problem. (Happy to hear from other fountains of course!)
I have an S37 fitted with KAD43's
I had an intermittent problem from new which was that the turbo on one side sometimes refused to come in (at 1600RPM) eventually it totally refused and I identified the problem (by swapping parts) as the little electronic box on the top of the engine. Volvo replaced it under guarentee.
On examining the box a transistor had burned out.
The problem went away but I believe now, 3 years later, that it is slowly returning. It seems (I think?) more of a problem under heavier load ie dirty bottom or lots of people on board.
My question (eventually) is "is this a problem that you have come across before and can there be something external to the electronic box causing the problem.
ta

 

[spannerman]

Hi David, I guess you mean the compressor wasn't cutting in at 1600rpm which is indeed controlled by a rpm sensing relay in the electrical box on top of the engine.
I have changed a few of these when they packed up, but not aware of any external factors that could cause it to fail. Unless Volvopaul knows of anything.
Have you had the oil checked/changed in the compressor, are the belts correctly tensioned, and is the belt tensioner bearing OK.
I see that some motors now have a 'Powerbooster' in this box which I believe has something to do with the relay controlling the compressor.

 

[DavidJ]

[ QUOTE ]
I guess you mean the compressor wasn't cutting in at 1600rpm

[/ QUOTE ]

Yes that right. Also I tension the belt to spec using the torque bar method and although I haven't changed the oil (only 300hrs) I do keep a check on level and it looks very clean on the dip stick.
I guess it could be the electronic box again but because I did some swopping around during my diagnostics I can't remember which side ended up with the new one. I can tell though when I'm on the boat again because the part number changed on the replacement box.
thanks for your comments

 

[volvopaul]

Ha ha had this problem before, you mean the supercharger at 1600 rpm not the turbo you wont see that till past 3000 rpm.
Any way whats happening is that the coils in the charger clutch are nearly burnt out and on there way going to earth out, net result is your little very exspensive black box up in smoke again.

Do you notice when the charger comes that the rev counter drops its reading though the engine is actually rising in revs ? well you need a new clutch assembly get one before you need a box ! the throttle has a kickdown facility too when you open up flat out the charger should kick in before 1600 ish revs as well, think thats all I can add to our Norwegian friend whos English is better than mine.

Incidentally had really hard day today working on a floating skip, ( Steel barge) thing thats why im home late! huff huff.

 

[DavidJ]

[ QUOTE ]
whats happening is that the coils in the charger clutch are nearly burnt out
Do you notice when the charger comes that the rev counter drops its reading though the engine is actually rising in revs ? well you need a new clutch assembly

[/ QUOTE ]

I'm a bit light on real data but my perception is that once the charger has switched in then the revs climb and all is well. It is an intemittent problem so impossible to 'make' it happen.
Is there an electrical check or comparison I can do?

Am I right in thinking that the problem is exacerbated when I have more load (dirty bottem or more people aboard) or is it my imagination.

 

[Peanuts]

Hi

Might be able to help on this one.
PM on its way - hopefully!!

 

[DavidJ]

Just got back from the Med leaving, thanks to you guys, the sweetest running engines ever.
The breakthrough advice was the diagnostic check "when the charger comes in that the rev counter drops its reading though the engine is actually rising in revs"
What I though was an intermittent problem was in fact a very repeatable one when doing the suggested check (with the boat out of gear)
The test gave me the confidence to buy a compressor clutch assembly (€340!!) which solved the problem and was quite easy to fit myself.
Interestingly the old clutch was completely shreaded but the coil tested and looked OK (4 ohms and nothing to earth, same as the new one) so the source of the problem still remains a mystery and the coil and clutch only come as a set anyway, so nothing wasted.
I think I've had the problem from new because opening up past 1600RPM on both engines has never been so sweet.
A big thanks once again