Engine compartment blower wiring on SO42i?

[DavidR]

Hi everyone, wondering if anyone can put me straight on the wiring for the ventilation blower on a 2007 Sun Odyssey 42i. I'm guessing it will be similar to many of the other SOs this age. I've recently replaced the failed blower but there is no power in the line running to it. Is this on the ignition circuit? And is it normally on all the time the engine is running? I have read that some models have a thermostat control but can't see one.

Any help appreciated. 

[plas50]

I recently replaced mine.
Mine was on the ingnition side.
And runs when the engine is running.
I don't appear to have a thermostat on the 42DS.
It gets quite warm in the engine compartment, especially in Spain, and the fan runs constant during engine running.

Andy

[Trevor]

Hello Davidr,

The SO42i will most likely have the same wiring as the SO42DS as they have the same hull. The fan is fed with a small relay located in the wiring behind the alternator. The relay is switched when the ignition is on. It is the same relay that enables the anchor winch to operate only when the engine is running. The relay is fed by a 7.5amp fuse located in a fuse holder just inboard of the battery switches under the aft cabin mattress. If the anchor winch works when the engine is running, it is not the relay at fault as it does both jobs.

I hopes this helps.

Trevor

[NZL50505]

I’m not a fan of the thermostat option.

Even if the engine isn’t hot enough to need a fan running, the blower still gives 2 other key benefits (1) improves oxygen flow to the engine (2) minimises engine room smells from the saloon. If you are used to a continuous blower and then try running your engine without it, you’ll soon notice an ‘engine smell’ the saloon.

[Andrei]

I agree it is not good to run the engine without the blower, thermostat or otherwise. An even better option for this blower, which I've seen on a newish boat by Hanse,  is wiring with off timer - the blower runs for additional 60(?) seconds after the ignition is turned off to safeguard against residual heat build up once the engine cooling water flow shuts off. 

[Andrei]

Also, I've got wiring for 2013 SO 409, it might be close enough to be useful.

Looks like the relay is triggered by the alternator output, not the ignition switch,  which makes sense to me. 






 

[Trevor]

The schematics are available on this website by going to specifications/manuals and finding the SO42DS schematics. The SO42DS is the same hull as the SO42i and the wiring of the hull is the same.

[OhWell]

Thank you for this thread.   

I've replaced the relay and the checked the 7.5 amp fuse on our 2001 43DS.   Still no power to the blower with the engine running.
  
Any other thoughts?   

Thanks 

[zaphod]

Sept 14, 2022 12:06:35 GMT OhWell said:

Thank you for this thread.   

I've replaced the relay and the checked the 7.5 amp fuse on our 2001 43DS.   Still no power to the blower with the engine running.
  
Any other thoughts?   

Thanks 

Are you getting power to the relay? Is the relay closing when the engine switch is on?

Time to break out the multimeter and start troubleshooting.

[OhWell]

Mystery solved.  On our 2001 there's a thermal switch in the negative wiring inside the blower hose so it will not come on until the engine space gets to around 100F.  You won't see voltage at the blower until the space heats up or you jump over the switch.   With reliance on big alternators these days it probably makes sense to just let it run all the time.  

[zaphod]

Sept 16, 2022 20:29:50 GMT OhWell said:

Mystery solved.  On our 2001 there's a thermal switch in the negative wiring inside the blower hose so it will not come on until the engine space gets to around 100F.  You won't see voltage at the blower until the space heats up or you jump over the switch.   With reliance on big alternators these days it probably makes sense to just let it run all the time.  

Ah that explains it! I would think itcwould make sense to have it run continuously to keep the engine compartment in negative pressure. Are you in a cold climate? Maybe the fan is wired that way to help the engine warm up faster or for cold starting?

[DavidR]

Sept 9, 2022 23:17:30 GMT DavidR said:

Hi everyone, wondering if anyone can put me straight on the wiring for the ventilation blower on a 2007 Sun Odyssey 42i. I'm guessing it will be similar to many of the other SOs this age. I've recently replaced the failed blower but there is no power in the line running to it. Is this on the ignition circuit? And is it normally on all the time the engine is running? I have read that some models have a thermostat control but can't see one.

Any help appreciated. 

Thanks for the great advice everyone. Problem sort now. As suggested no thermostat and problem was a short. Looking forward to a saloon without the fumes!