Fan switches

Post by **katanaman** » Sat Aug 18, 2007 5:59 pm

I think its a different type your on about Tom. I think the type your on about is a pipe that you screw a normal radiator type switch into, little more than a bimetallic switch. The type I used is a thermistor and a transistor along with a variable pot so you can tune the temp. Completely electronic hence why it has a relay as there isn't anyway for the transistor to dump heat when its sitting on a 90 deg pipe in the first place. Its a good idea to use a relay with your type of switch as well by the way, especially if your running big fans as it will stop the switch from welding itself or burning the contacts.

The Original Tom · Post by **The Original Tom** » Sat Aug 18, 2007 7:33 pm

Although I mentioned the X-eng one (linked) I don't have one, just suggested it's a good one. 30A won't burn out as most fans draw only 7A constant, my first one was only 5A!
The switch I have, which has the capillary, does now have a relay attached. The NO terminal was rated at a max of 6A, and although this was ok for the original fan I've now relegated that to the "on load" fan, it won't deal with the twin-fan setup from a Disco 2 I've bought for the main fans.

Post by **katanaman** » Sat Aug 18, 2007 9:32 pm

Depends on the size of fan I guess but most of the after market fans (13") are in the region of 25 amp constant. I don't know what the starting current will be but it will be a fair bit higher, 7 amp is a bit weedy if you ask me.

The Original Tom · Post by **The Original Tom** » Mon Aug 20, 2007 8:00 pm

Well just going on what I know, that 6A fan was soley resonsible for cooling a 2.5l engine for the best part of 6 years and it never overheated to my knowlege (certainly in the 2 years I had it).