Engine Blower (Extractor) Wiring

[Ammonite]

Please can someone more electrically minded than me explain why there are two relays for the engine room blower on my Moody 36? Also, what would be the best way of changing this so that the fan continues to run after the ignition is switched off.

 

[starfire]

It looks like the lower relay is for manual control of the fan, the top one has thermostat contacts wired to it, so should continue running until things have cooled down.

Maybe a faulty thermostat or relay ?
Also, check the 2nd fuse from the left on the diagram.

 

[Ammonite]

Thanks but there isn't an override / manual switch and my understanding is that the fan will only run when the thermo switch closes. This operates the thermostat relay but won't operate the fan unless the other relay is on which also requires the ignition to be on...or at least that is my current take.

 

[Ammonite]

My current thinking is remove the engine fan relay and to take the load (supply) for the thermostat relay directly from the breaker as I can't see the need for the engine fan relay. Both relays are suitably rated for the fan. To ensure that the fan then runs after the engine and ignition are switched off (when it's most needed after a long run) I'm thinking of adding an adjustable timer delay relay to ignition feed so that it will run for a predetermined time after the ignition is switched off (provided the thermostat is closed). Alternatively I could forget the ignition feed to the thermostat and take this directly from the battery switch so the fan runs whenever the thermostat closes (50 degrees) regardless of the whether the ignition is on. Thoughts?