Testing the radiator fan

[Harrie Harrison]

New poster! (less than 10 posts)

Is there a clever way of checking that the radiator fan will start up automatically as the engine gets to max temp without risking overheating? Before I bought my 5GT I deliberately kept it idling until the cooling fan kicked-in (the temp needle was on the second line) to prove it worked but now that I own the car, I am less inclined to tempt fate!
I have just changed the oil filter and owing to the previous owner's choice of replacement radiator the job was complicated by a water hose being in just the wrong place and blocking the filter from unscrewing right next to the temperature switch. Consequently I am worried that if I have knackered the wiring when struggling with the filter I won't know until the car overheats! I know the fan works so it is just how can I simulate high temperature?
Grateful for your advice, HH

[Mr Raider]

Bottom rad hose and oil filter area is fairly snug, do you have a picture? If you connected longer wires to the fan switch then carefully dipped the sensor side in hot water this would simulate engine getting hot so rad fan would kick in.

Or run it up to temperature on idle keeping a close eye on the gauge and where the fan cut in beforem to see if it does still work as it should.

[Harrie Harrison]

New poster! (less than 10 posts)

Thanks for the advice. I was hoping to test it without taking the switch out and draining the coolant. Sudden thought came to me while looking at the wiring diagrams this evening - what if i just disconnect the two wires to the temperature switch and touched them together? I assume that if the fan starts then it indicates the switch 'works'? (electrics are not my strongest specialist subject!)

[Matt Cole]

New poster! (less than 10 posts)

Thanks for the advice. I was hoping to test it without taking the switch out and draining the coolant. Sudden thought came to me while looking at the wiring diagrams this evening - what if i just disconnect the two wires to the temperature switch and touched them together? I assume that if the fan starts then it indicates the switch 'works'? (electrics are not my strongest specialist subject!)

Yes, bridge the two sensor wires and the relay will start the fan.

[Trevhib]

Aye. That will show the fan's electrical circuit works but it won't prove that the thermostatic switch is working.

To overheat the car you really have to go some. Way past the second line. For me it's a matter of refitting everything and testing it by allowing the car to heat up and see if the fan cuts in. If it obviously doesn't, just switch the car off and go back to the wiring/switch to investigate.

If you are worried, just fit a manual toggle switch to the thermo switch's wires, so you can force the fan to run if the car gets hotter than you want.

[francob80]

Not ideal I know but previous owner wired my fan to a switch so I can use when I feel the car is running a little hot which is rare to be honest.

[Harrie Harrison]

New poster! (less than 10 posts)

Many thanks for the advice. I will short the two wires to check the fan then test it by letting it run hot and watch the gauge/fan.

[Trevhib]

Let us know how you get on