Fan Switch Wiring And Temperature

[MarkBzero]

Hi,

At last the engine is running, in th old car I use a variable fan switch but with ST170 I am using retro ford water rail which includes a fan switch.

1. Does any one have a wiring diagram you can share, the fan switch only has one terminal?

2. What temperature should fan come on and switch off?

3. Currently using rad with coolant cap, but want to block of and fit inline filler in top hose so I do not need to flip nose forward when checking coolant level. How do I block off old rad? It has a over flow spill and suck pipe.

4. What thread size is the temperature sender where the the wire fits through eyelet? Not metric and looks like a fine thread.

Thank you.

Edited July 30, 2017 by MarkBzero

[Peter Bell]

Answer to part of your questions is you can buy just a plain blanking cap for the rad, and you will need to block off the overflow pipe.

[Big Jim]

One way of doing it. http://nw.rhocar.org/fan%20wiring.htm obviously there are other ways.

[tractor]

there are two connections on the switch you run a ignition twelve volts through it to your fan relay the it will switch on at the set temp if you look on retro fords website it may have the info

[MarkBzero]

Answer to part of your questions is you can buy just a plain blanking cap for the rad, and you will need to block off the overflow pipe.

Thank you, lots of different blanking caps, it's the standard GBS zero rad do you have a part number/link please?

[MarkBzero]

#1

Assumption - I dont know - just surmising

If the switch only has one terminal - is it switching to ground? - also assuming the switch body is grounded to chassis somewhere.

 

So your circuit would be on the coil side of the fan relay -

 

12v -> Fuse -> (Relay coil 1 .... Relay coil 2) -> (fan switch line ... Ground)

 

-> are wires

... are internal to the relay or switch

 

So power direct from battery or ignition supply? Thanks

[MarkBzero]

One way of doing it. http://nw.rhocar.org/fan%20wiring.htm obviously there are other ways.

Thanks Jim, I understand this diagram and if I buy new switch with two terminals I could make this work. It's weird because the retroford thermostat on their website has two terminals. I might just buy one.

[alanrichey]

It also depends on whether you use a switched earth or a switched live. If you use a switched earth (i.e. one side of the fan is permanently at 12V) and the sensor is screwed into the block then it needs only one terminal. If you are using switched live or the sensor is not screwed into the block then you need 2 terminals.

[fry61]

Without an electrical circulating pump for the engine coolant is there any point in the fan running when the engine is stopped?

 

NW area's circuit is designed to take out the fan load when cranking a hot engine & a relay is best practise for the heavy fan current, so ignition supply -- fan "earthed" through starter windings & relay switched by the supplied 'stat with ignition live supply.

 

NW's method gives the best battery power to the starter motor.

[IanS]

In the 1930s most cars did not have a water circulating pump and depended on thermocycle to circulate the water.

If the top of the radiator is above the top of the engine block and the bottom is level with or below the inlet to the block there will be some thermocycle circulation.

The 1930s cars did have the top of the radiator a long way above the top of the engine to achieve good thermocycle circulation.

Personally I stop the fan when the engine stops to save the battery.

[fry61]

That's the way they worked back when I were a lad --- but to-day most 7 style cars have a problem with venting all the air from system because the rad is at or even below the top of the engine, so no thermo-syphon.

[MarkBzero]

Thank you for all the replies, away this weekend so will wire up next weekend.

Cheers