Hello,

At present I have wired my fan through the temperature switch to power with a manaul over ride switch in parralell to the temperature switch. This was during one of thoose late night efforts and then in the morning I suddenly though t I should have probably used a relay.

Should I pull of all the nice binding tape and start again?

Cheers Blair

To be on the safe side i'd use a relay. Fans do draw a lot of current, both the temperature switch and override switch might burn out. All depends on their rating really.

I used a relay on mine, probably best otherwise you will always be thinking "should I have used a relay" and it will bug you.

Rich.

Definately use the relay

would say relay

It's not the running that will kill your switches, it's the kick-in... relay, you know it makes sense.

TBH, the temperature switch in the cooling system will most likely take the current. However the same cannot be said of the over-ride switch.

Use a relay!

Thanks Guys,

Moral of the storey is draw up your circuits when you are awake and wire them when you are asleep!!!

Off to buy a relay with a built in fuse so I can mount near the radiator and not need to run to many new wires.

Not sure what I'm talking about here but... the micra rad that I have fitted is wired originally by nissan and it does not have a relay fitted.
If Nissan don't think it needs one... I'm kinda thinking... maybe I don't need one..
Is my logic ok.. or way off?
Cheers guys

Depends on the quality of switch that Nissan used in the original car! They may have used one with big meaty contacts that could take the arcing. Other car makers used finer and more delicate contacts that always require a relay.
Anything that has big coils in it (like motors) take a big current hit when they first connect, then give a big back-EMF when disconnected (EMF = electroMotive Force - in other words, a short, sharp burst of high voltage and current for a fraction of a second). The back-EMF causes arcing that burns inadequate contacts. If in doubt, fit a relay!

David

Use a relay definatley. Like hellfire said its the draw when it kicks in that kills it. Use a heavier duty one aswell as the contacts on the smaller ones stick.

Relays are a safe way of taking current away from your switches.

I was going to have my fan come on with the ignition and run all the time. Not a good idea? What do you think?
Cheers
Jon

I'm with the previous poster who said if all the bits come out of a micra and that doesn't have a relay then my car doesn't need one either. The micra switch is obviously rated for its purpose. They are a very competently designed bus!
If I were putting a mishmash of different bits together, the relay would go in for sure!
The back emf on a motor would normally be slightly below the 12V supplying it. Contact arcing on switch off is a very short lived affair due to motor inductance, a small capacitor would catch it effectively: most motors include such caps for commutator supression.
Current surge on switch on is very real & on this size motor could be several tens of amps lasting for a couple of hundred milliseconds until the motor spins up. Not a big deal for a switch 'cos it happens when everything is cold, for a short period, more of a fuse issue.
cheers
Bob

Mine comes on with the ignition, but doesn't have a relay - it's the premier wiring loom and no probs so far.

Pat...