Originally I planned to fit radiator fan switch in a joiner between thermostat housing outlet and top of radiator but may not have the room.

But there wil be a long joiner in the bottom hoseso the switch will sit in the cooled water coming out of the radiator.

What would be a good value to have the radiator fan(s) switch on?

Engine is 1600 crossflow, 88 degree C thermostat. I have no idea of temperature drop across radiator.

hmm, i don't know, but wouldn't the temperature of the water in the top hose always give the engine water temp, whereas the bottom hose might vary depending on a lot of factors, like outside air temp, air speed over the radiator, and maybe other stuff.

i think you 'could' get situations where your engine is overheating, but because its below 0 degrees outside, your raditors cooling a lot more and the fan doesn't come on?
^ but then the waters colder going in... so would it be a problem...? lol i don't know. if you've got space for a hose, why wouldn't you have space for a joiner with temp sender? they're not much bigger than the hose itself? or is it more a length issue?

[Edited on 18/1/10 by blakep82]

Hi
I ran my fan switch in my bottom hose on my 1600 crossflow and the only problem I found was that on hot days the fan didn't run/cut in properly enough to keep the engine at a safe coolness, I was always worrying it was gonna overheat so it took the fun away from driving it. Saying that, It never did overheat but I moved it to the top hose and was suprised how much more the fan cut in and kept the temp at a more stable heat.
hope that helps.

Gary

What type of radiator ?

If its an old fashioned brass rad solder a brass nut to the top tank of the rad. I