KAD32 Supercharger still on at idle

Montemar

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Hello
we have had a Sealine S23 since March, it had an engine service two weeks ago.
After a trip from Poole back to Weymouth we found the compressor did not disengage at 1400 rpm as normal. It cuts out at 2800 rpm so no problem there but is still droning at low revs and engine is lumpy.
I feel sure it must be a simple fault.
Please give me some ideas of where I can start looking for the problem components.
Thanks.
 

volvopaul

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The charger takes postive and negative to pull the clutch in, its permanently wired positive when the ignition is turned on, the black box relay cuts in and out by a signal from the speed sensor, now there are many reason why its still in.

The throttle arm has a magnetic switch on it to bring in the SC from idle if you want the kickdown feeling, it may be the switch thats failed, or a metalic object is pressing on it.


The Earth wire has grounded sending negative supply to the clutch.

The relay box has melted and shorted inside.

The speed sensor has failed sending the cut in signal.

Lastly the clutch has been to hot and has fused together.

Disconnect the plug on the clutch, if its still in then its the clutch.

Test the 2 wires with a meter looking for 12 volts or more.
 

Montemar

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Fantastic. This I can understand.
My multimeter and I now have a whole new Saturday morning!
Que sera sera.
Your help is very much appreciated. I shall report back on what I find.
M.
 

Peanuts

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Hi

Although the basics have already been outlined by VP I would just like to add my view.

You mention that the S/C disconnects at the top end so we know the magnetic clutch works and that the speed relay is working (at the top end).
I would disconnect the S/C at the 2 pin block (about 6" from the S/C), then with the engine running and your multimeter plugged into the engine side of the socket, + into the red cable and - into the white cable. At idle it should be 0 V, increase upto 1700rpm and check for 12V supply coming on, if you were to increase upto 2600 then it would drop but then you know that already happens. I think that you will find 12V at idle, I would check the wiring within the black box and the speed relay - not that there is much to check on the relay.

I have to admit I am wondering if there is any relationship between the engine service and this problem?

Let us know how you get on.
 

Montemar

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Thank you for refining Volvopauls suggestions.
We have used the boat since the service though not hard largely because of weather however today we got it flat out in Weymouth Bay. 28 knots but rather bouncy! It occurred to me that it could be related to a bit of serious use.
Gracias.
 

Montemar

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I went back to see if the supercharger was still engaged at low speeds and inevitably it was now working normally.
I checked the wiring, could not find a ground to earth, separated and remade all connections. The only possibility was the large multicored cable that comes in through a gland on the front of the black box. It was loose and could be pushed in, the locking ring didn't as it seemed to be missing a matching thread. As I do not have a wiring diagram I cannot say if this had been the fault.

What I did not try was restarting the engine after the fault originally showed. It could be that with the ignition off the companion plate on the end of the supercharger sprang back.

However thanks to you both for your help. I see that a new rotation speed relay is a real L&A job so keep my fingers crossed it was the loose multicore cable!
 

RIN

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Hope it is all right for you now.

We had a failure of the magnetic switch that VP mentions (the kickdown switch) it was intermittent but eventually failed altogether (when we were on a cruise up the Seine). The failure caused the compressor stay on all the time. As we had twin engines it was easy to swap bits over until we identified the cause. Also useful is a compressor switch we had retro fitted to the control box (just put a waterproof switch in the white wire inside the control box) so we were able to manually switch the compressors off. If it is the switch that has gone, its £160 squid. Peanuts can tell you how to make one for £30 though
 

Montemar

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Thank you.
Actually I could not see the kickdown switch. Is it on the engine or with the control levers.
I suppose one could just pull out the plug at the supercharger in extremis.
 
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