Richmac Posted May 31 Report Posted May 31 (edited) Please wait while image is uploading... I have a TR4 fitted with an old electric fan. I turned the thermostat down to minimum (60) and left the car ticking over and it didn't kick in when the temperature gauge read 70. Is there another way of testing the fan motor and thermostat without just running the car up please Thanks Richard Edited May 31 by Richmac Add photo Quote
RobH Posted May 31 Report Posted May 31 The only way with that thermostat would be to take the sensor out of the rad or pipe, set the thermostat to max then and put the sensor it in a pan of water at near 100C while measuring the water temperature. As the water cools past the thermostat setting, the fan should turn off. You should be able to adjust the thermostat down to turn the fan on again, and that way check the setting against the actual temperature at a number of steps If you do that be very careful not the bend the capillary-tube sharply. If you fracture it you will need a new thermostat. Quote
Richmac Posted May 31 Author Report Posted May 31 Thanks Rob. Is there a way I can bridge the terminals to activate the fan to see if it even works please Thanks Richard Quote
jerrytr5 Posted May 31 Report Posted May 31 Identify the wires from the fan motor & connect to 12v supply. Jerry Quote
RobH Posted May 31 Report Posted May 31 From the photo It looks to me as though that thermostat only has two connection tags, with two wires going to each, in which case it must just be a 'make' contact. My guess would be that the green wire is ignition-switched supply so you could check that first with a meter or test lamp. I think if you bridged the terminals with a wire link, the fan should run. Be careful not to earth the link as it will be at 12V. Depending on how it is wired, you may need the ignition switched on. If it has been wired properly there should be a fuse in the supply line to the thermostat so if it doesn't run that is the first thing to look for. Quote
Richmac Posted May 31 Author Report Posted May 31 Thanks Rob excellent advice as usual, much appreciated Quote
Richmac Posted June 1 Author Report Posted June 1 No power to the thermostat on any terminal when tested with a test lamp. All fuses I can find are good but can't decipher if any are serving the fan. Mmm Quote
james christie Posted June 1 Report Posted June 1 (edited) As it seems to be the flavour of last week. If anybody wants a period pusher Kenlowe fan FOC + postage from France. Will he put his hand up or send me a PM No relay, no switch, just the fan with its L shaped legs james Edited June 1 by james christie Quote
RobH Posted June 1 Report Posted June 1 3 hours ago, Richmac said: No power to the thermostat on any terminal when tested with a test lamp. All fuses I can find are good but can't decipher if any are serving the fan. Mmm Pity - not much you can do other than try to trace the wires from the thermostat and find out where they go. Is there a manual override switch? I would think there is from the way it is wired. My guess for starters would be: Green - power in Blue wire and one Blue/grey wire - to override switch ( this just shorts out the thermostat contacts) other Blue/grey - switched power to fan motor ( other side of motor is earthed ). You could disconnect both blue/grey wires and use the test lamp from 12V to each wire in turn. If it lights on one of them that is probably the motor power lead. You could connect that to 12V to see if the fan runs, but make the connection through a 20A fuse just in case. Quote
Brianjone5 Posted June 2 Report Posted June 2 I have a fan like the one James Christie offers. I especially like that it is free-standing. It may be positioned close to the the radiator, but has no contact with it. No zip ties through the radiator fins, no brackets to weld on. This makes servicing the radiator or the fan much easier. Quote
RogerH Posted June 2 Report Posted June 2 Hi Brian, that fan is not really free standing. The 'L' shaped brackets MUST be attached somewhere - otherwise it will fly away. Roger Quote
james christie Posted June 2 Report Posted June 2 In fact Roger, if you have a non functioning engine, you can switch the fan on and using the battery you can advance the car, provided the legs are attached. But you don't have to believe me.......🤪 james Quote
rcreweread Posted June 2 Report Posted June 2 1 hour ago, james christie said: In fact Roger, if you have a non functioning engine, you can switch the fan on and using the battery you can advance the car, provided the legs are attached. But you don't have to believe me.......🤪 james it obviously came off Concorde - I'm surprised Roger didn't recognise it Cheers Rich Quote
Richmac Posted June 2 Author Report Posted June 2 On 6/1/2026 at 5:43 PM, RobH said: Pity - not much you can do other than try to trace the wires from the thermostat and find out where they go. Is there a manual override switch? I would think there is from the way it is wired. My guess for starters would be: Green - power in Blue wire and one Blue/grey wire - to override switch ( this just shorts out the thermostat contacts) other Blue/grey - switched power to fan motor ( other side of motor is earthed ). You could disconnect both blue/grey wires and use the test lamp from 12V to each wire in turn. If it lights on one of them that is probably the motor power lead. You could connect that to 12V to see if the fan runs, but make the connection through a 20A fuse just in case. Hi Rob The wires are wrapped in the loom which I'm reluctant to unveil. There is a manual override switch with two blue wires and one black. The thermostat does indeed only have two terminals. With one green wire the other three are all blue. Thank you for trying to help me I'm rubbish at electrics Quote
RobH Posted June 2 Report Posted June 2 (edited) Ah - the 'grey stripe' I thought was there in your first photo is obviously a reflection then - sorry. Using the same colour wires does make things difficult. I think the manual switch must be illuminated and the black wire is an earth connection for the lamp. The wiring is probably like this: Disconnect the green wire from the thermal switch in case that connects to something earthed - and insulate the end. Then If you take both blue wires off the right-hand terminal and connect them in turn to 12V , one should light the bulb in the switch and the other should run the fan - just make a note of which is which. ( I suggest you do that power connection connection through a 20A fuse just in case.) If the fan runs you could re-connect the two blue wires and run a new power lead to the thermal switch in place of the green wire, to check the operation of both switches. After that it's a question if why there is no supply on the green wire. Edited June 2 by RobH Quote
Richmac Posted June 3 Author Report Posted June 3 Thanks Rob. You were correct running power to the two blue wires one does run the fan, so at least I know it works, and the other does light the manual switch light. However if I then run 12v to the green connection I get nothing from the override switch Quote
RobH Posted June 3 Report Posted June 3 OK - then how about lifting the blue wire from the left-hand terminal on the thermal switch and connecting 12V to that wire. That should put power directly on the override switch and it should then work the fan when you operate it. If it doesn't, either that switch is faulty or there is a break in that blue wire. If the switch does work, there is something odd with the connections at the thermal switch. Quote
RobH Posted June 3 Report Posted June 3 In that case it's possible that both the manual switch and thermal switches have been damaged - maybe by the motor start-up current which could be quite high. It's always a good idea to use a relay for motor switching, so the switches themselves only carry the relay operating current, and let the relay contacts do the hard work. Do you have a test meter with an Ohms range? Quote
RobH Posted June 3 Report Posted June 3 That would be fine for checking that the blue wire you have just tested does actually go to the manual switch and for trying to find out where that green wire goes, so that you can at least get power to the thermal switch. Other than that you are now at the point where replacement of the switches is probably necessary. If you are doing that it would be an opportune time to include a relay: Quote
Richmac Posted June 4 Author Report Posted June 4 Thanks Rob really appreciate the time and effort you have put in to try and help me. I really hope I can help you with something one day Kind regards Richard Quote
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