Fan Thermostat Switch

[Guest Wozzer]

Hi All,

 

I want to control my electric fan from a switch in the top rad hose. A friend of mine will braise a threaded nut into a length of 32mm copper pipe which I can insert into the hose.

 

Question: Does anyone know which scrappie car to pinch one off that will be a metric (or common) thread and switch the fan on and off at the correct temperature?

 

Warren

[Guest salty_monk]

Pretty sure a lot of people use the Fiesta sender....

[Big Jim]

you want a 22mm thread in your boss, then either the switch from a Fiesta will fit, or a switch from a Vauxhall diesel (I believe) or you can get "pucka" switches from Premier wiring (good people) or even Demon theives nowadays, and you have a choice of a varied selection of temps "swich on's"

[steve in stockport]

peugeot 205 fan switch is 22mm thread as Jim said, fan comes on at 88 deg and knocks off at 79 deg, vauxhalls opens at 99 and knocks off at 95.

or go to your local spares shop and check the catalogues for the switch that gives the temp range and fitting you want

 

Steve

[Peter Bell]

I bought mine from a rad specialist with the radiator, it fits in the bottom of the rad and switches on at 78°. The man said that the problem often with a high temp switch was that by the time the fan came on it was almost too late. The previous one I had was about 90°. It has been fine but ocaisionally on a very hot day when driving on a motor way the fan runs all the time!

Peter.

[Guest Ant]

The previous one I had was about 90°. It has been fine but ocaisionally on a very hot day when driving on a motor way the fan runs all the time!

Peter.

Was it in the bottom hose doing this, or in the top hose?

 

Ant

[Big Jim]

it fits in the bottom of the rad and switches on at 78°. The man said that the problem often with a high temp switch was that by the time the fan came on it was almost too late

It's no wonder with it fitted in the bottom of the rad!

Lets do this logically............What part of the cooling system do you want to ultimately control the temparature of? The engine or the radiator? I would say the engine. so you want to measure the temperature of the water in the engine, and make alterations by cooling the water entering the engine (ie. through the rad) so you switch the fan on and off as required. If you have the switch in the bottom of the rad, In my opinion you have less control. It will work to a degree, but it's not as good.

[Peter Bell]

OK Jim I'll try to defend this a bit, this is a standard rad with a temperature sensor in the bottom, (Fiat 127) fine aluminium finned, copper tubes. By making sure the temperature of the water returning to the engine is reasonably cool you are providing a temperature gradient to allow the engine to cool. If you are worried about overcooling, (not much fear in a Hood I think) water flow will be controlled by the thermostat anyway, which is sensing the temperature of the water coming from the engine. I had a problem with a different car where the sensor was high up in the system and when the coolant level dropped due to it boiling, the sensor no longer thought that it was hot!

Peter

[Big Jim]

I had a problem with a different car where the sensor was high up in the system and when the coolant level dropped due to it boiling, the sensor no longer thought that it was hot!

Yes, but I'll bet it was in the radiator, if the sensor is in the top hose, or thermostat housing, then the water has to pass it (once the stat has opened) and if there's not enough to do that, then it's not going to flow through the rad anyway, so your stat in the bottom of the rad won't do anything either.

I will still argue that it's the engine coolant that you want control over, changing the temparature of the coolant in the radiator obviously has an effect on the engine coolant, but you cam leave yourself open to hot/cold spots in the rad, blockages etc.

I know of a guy with a very nice Sierra cosworth, in fact it's showrome condition, he has a very expensive alloy rad in it, with the temp sensor down near to the bottom of the rad, the problem is, it's in a cold spot in the rad, and his engine keeps overheating, he's had it back to the main speciallist at least 3 times for them to try and sort it, but they haven't managed to yet!

In theory, if set up correctly, and all the bits work, then Yes it'll work, but there's no choice if it's in the top hose, it just will work.